Nysson parvispinosus Reed, 1894: 641, by original designation and monotypy.

Cresson can be separated from other South American nyssonine wasps by the combination of i) metatibia lacking teeth, with bristles that clearly arise from an articulation in a socket; ii) metasomal sterna lacking lateral lobes as opposed to lobes present (compare Fig. 5 herein with fig. 154 in Bohart and Menke 1976); iii) metasomal terga with posterior margins thickened and appearing double-edged (Fig. 4, yellow curly bracket) versus simple and iv) a Υ-shaped crest on the lower frontal area with the apices of the paired arms recurved (Figs 1–3). Feature i) separates Cresson from Idionysson Pate, 1940, Metanysson Ashmead, 1899, Neonysson Bohart, 1968, and Zanysson Rohwer, 1914, ii) separates it from both Antomartinezius and Perisson, iii) separates it from Losada Pate, 1940 and Nysson and iv) from Epinysson Pate, 1935, Foxia Ashmead, 1898 and all aforementioned genera except Antomartinezius and Perisson.

Colouration: Black with white to cream coloured markings on face, pronotal collar (rarely absent), pronotal lobe, scutellum (rarely absent), legs, subapical bands on most terga, sometimes on sterna; red markings on metasoma absent to extensive. Both sexes with labrum and base of mandible pale, female with clypeus pale laterally, black medially, male clypeus entirely pale except lip orange-brown.

Pubescence: Silvery appressed to subappressed setae extensive on face, genal area, dorsal surface of pronotum, most of mesopleuron (sparser anteriorly and ventrally, absent posteriorly), posterolaterally on scutellum, metanotum, dorsolateral area of propodeum and sometimes on T1, setae of scutellum and metanotum anteriorly or anterolaterally oriented; fine erect setae longer on upper part of face, shorter on mesoscutum and mesopleuron, vertically oriented dense row of short setae occupying space between extreme apical margin of terga and base of succeeding tergum, metasomal sterna with scattered longer erect setae; male with median setal fringes on S2–S5 situated in a gap in the apical sternal depressions, lateralmost fringe setae longest, posteromedially oriented but sparser than more posteriorly oriented remaining fringe setae.

Surface sculpture: Microsculpture largely absent, integument shiny, punctures bimodal in size on face and mesoscutum, minute punctures sparsely scattered among interspaces between larger mostly dense punctures; larger punctures especially on face and mesoscutum with minute punctures at their bottoms and often with several punctures aggregated in groups with edges raised, sometimes giving somewhat striate appearance; minute punctures more numerous on metasomal terga and sterna among distinct larger punctures; junctions between mesoscutum and scutellum and between meso- and metapleuron foveate, the latter finely so; lateral surface of pronotum and posterodorsal part of lateral surface of propodeum obliquely costate; posterior portion of mesopleuron, metapleuron and rest of lateral surface of propodeum generally lacking sculpture, glassy smooth; posterior surface of propodeum coarsely sculptured; metapostnotum rugoso-striate dorsally. Portion of metasomal terga posterior to graduli (usually hidden beneath preceding tergum) imbricate, dull; sterna with similar imbricate areas more extensive. Metasomal terga and sterna with most punctures separated by distance greater than their diameters, except last metasomal tergum with coarse, irregularly shaped, almost crowded punctures; last visible sternum with small, scattered punctures; apical impressed tergal and sternal depressions with row of punctures at their base.

Structure: Head 1.3–1.5 × wider than long; labrum short, transverse, apical margin slightly concave to transverse medially; clypeus short, apicomedially concave with pronounced bevelled edge, lip approximately half as wide as clypeus; supraclypeal area small, sometimes hidden beneath ventral expansion of frontal crest, crest Ϋ-shaped, ventral margin of crest swollen with angulate ventral incision, in frontal view crest obscures the medial margin of the antennal socket lateroventrally, medially the crest is conspicuously developed, almost lamellate, dorsal arms less developed, recurved, space between median lamella and entire recurved arm with one dorsolaterally oriented lamella and varying number of subparallel carinae; space between lateral margin of supra-antennal area and compound eye with frontal depression extending upwards for a variable distance below lower tangent of median ocellus, dorsal margin of depression often ill defined; inner margin of compound eyes markedly convergent below, shortest distance between them at base of clypeus; occipital and hypostomal carinae complete, lamellate. Scape longer than wide, slightly produced basoventrally, integument somewhat translucent for apicoventral one-third of length; pedicel with medial surface globose, conspicuously narrowed towards base, lateral surface straighter; male apical flagellomere falcate, concave below narrowing to acute apex. Pronotum with vertical carina that in dorsal view appears as a tooth, pronotal collar in dorsal view transverse anteromedially, convex anterolaterally; in profile gradually rounded onto anterior declivitous surface except abruptly and angulately so medially. Mesoscutum posterolaterally markedly reflexed upward, projecting over medial margin of tegula. Lateral propodeal spine conspicuous, acute. Mesotibia of male with one apical spine, mesobasitarsus of male with ventral setal fringe; female lacking rake spines on protarsus; metatibia slightly concave apicodorsally, extreme apex angulate dorsally, lacking robust spines or teeth; arolia in both sexes small. Three submarginal cells, second cell petiolate; stigma subequal in size to prestigma; hindwing media diverging beyond cu-a by more than twice the length of the latter; jugal lobe somewhat larger than tegula. Metasomal terga posterior margins double-edged. T2 transversely depressed anteriorly. Apical tergum of both sexes with apicolateral margin spinose; in females, the medial pair longer than others, in males the single median spine is short. S2 swollen anteromedially and depressed anterolaterally. Metasomal sterna not extended laterally as lobes, male S2–S5 with apical sternal depression abruptly absent medially, this area in female sometimes slightly concave.

55 ♀, 47 ♂: Lectotype ♀; Chile, Colchagua Province [Region VI]; 1890; E.C. Reed; MCZ-ENT-17200; Additional material: 1 ♂; • Chile [Region IX], 20 km E. of Temuco; [-38.7 -72.35]; 7.i.1951; Ross and Michelbacher; CAS; • 1 ♀: [Region VII] Curicó Prov., Fundo La Montaña, Estero La Palma at Rio Teno, 6 km E. of Los Queñes; [-35.00 -70.75]; 4.i.1967; M.E. Irwin; CAS; • 1 ♀; Valparaiso Province [Region V], Valparaiso; [-33 -71.5]; 26.xi.1919; P. Herbst; MCZ; MCZ-ENT 00731885; • 1 ♀; identical data as previous; CAS; • 1 ♀; identical data as previous; 12.i.1921; MCZ (MCZ-ENT 00731886); • 2 ♀, 3 ♂; identical data to MCZ-ENT 00721886; CAS; • 1 ♀; Valparaiso [Region V], Concon; [-32.9 -71.5]; 74.xii.1910; P. Herbst; MCZ; MCZ-ENT 00731884; • 1 ♂; identical data to MCZ-ENT 00731884; CAS; • 1 ♂; [Region V], Rio Blanco; 7.xii.1917; P. Herbst; CAS; • 1 ♀; Valparaiso Province, [Region V] Olmué; [-33.0 -71.2]; 4.ii.1920; P. Herbst; MCZ; MCZ-ENT 00731883; • 1 ♂ (dissection code 65-xi-250); [Region V] Perales, Quilpué; [-33.05 -71.4]; 4.ii.1925; P. Herbst; CAS; • 1 ♀; Valparaiso Province [Region V]; Marga-Marga; 9.i.1919; P. Herbst; MCZ; MCZ-ENT 00731880; • 1 ♂; Santiago Province [Region Metropolitana], Cerros de Tiltil; [-33.1 -70.9]; 18.i.1919; P. Herbst; MCZ; MCZ-ENT 00731881; • 1 ♂ identical data as previous; 2000m; i.1920; MCZ; MCZ-ENT 00731882; • 1 ♂ (“homotype” A.R. Menke); [Region V], Valparaiso; 19.i.1921; P. Herbst; UCDC; • 1 ♀; [Region V], Altos de Lliu Lliu; [-33.1 -70.9]; 20.i.1919; P. Herbst; UCDC; • 1 ♂; [Region Metropolitana], Santiago; 1922; F. Jaffuel; UCDC; • 1 ♀; [Region Metropolitana], Santiago, Maipu, Quebrada de La Plata; 26.xii.1966; L. Stange; UCDC; • 1 ♀; [Region IV], 10 km E. of Fray Jorge Nat[iona]l P[ar]k; [-30.6 -71.6]; 28.xii.1966; dry wash; M.E. Irwin; CAS; • 2 ♂, 1 ♀; Region IV, El Pangue; -30.164 -70.664; 1700m; A Ugarte; PCYU; • 33 ♂, 40 ♀; Region III, 13.5 km W. of Los Sapos; -28.019 -70.554; 500m; 22–25.x.2010; pan traps; L. Packer; CAS, MNHN, PCYU, UCDC and ZMBH; • 1♂; Region III, Rd. to Pastos Largos; -28.164 -69.791; 2100m; 6.xi.–11.xii.2013; S. Monckton and J. Postlethwaite; pan trap; PCYU; • 1 ♀; Chile; UCDC.

The type species of the genus can be differentiated from the new species most easily by the more extensive red colouration of the metasoma in both sexes with T1–T2 entirely red (except for the extreme anterior margin and one male has a small posteromedial dark mark on T2) (Figs 12–14). Females usually also have T3 entirely red. The other species have T1 and T2 black at least medially, although T1 is usually almost entirely black (see Figs 24, 31). The pronotal collar is relatively longer, at least two-thirds as long as MOD, whereas in the two other species it is approximately ½ as long as MOD (compare Figs 34 and 35).

Lectotype Female (Fig. 10)

Dimensions: Body length 6.1 mm, head width 2.05 mm, forewing length 4.4 mm, ITW 1.15 mm.

Colouration: Black except as follows: cream to pale yellow on labrum, basal half of mandible (rest orange to red-brown), clypeus lateral one-third (entire apical bevelled region and lip orange-brown), small semicircular-triangular mark on upper paraocular area adjacent to compound eye, small spot on genal area above adjacent to compound eye; large lateral marks on pronotal collar almost twice as wide as the space that separates them, pronotal lobe, lateral spot on scutellum, narrow oblique mark in front of mesocoxa, small apicolateral mark on meso- and metacoxae, apicoventral two-thirds of profemur, narrow stripe on anterior surface of pro- and mesotibiae (suffused with orange on protibia), narrow dorsal stripe on metatibia (rest of legs dark brown, except metatibia posterior surface and all tarsi orange to orange-brown), medially interrupted narrow subapical bands on T1–T5. Most of ventral surface of scape yellow brown. Following parts orange-red: T1 and T2, T3 laterally; S1 and S2 (both suffused with red-brown medially), S3 narrowly subapically, S4 narrowly apicolaterally. Apical tergal and sternal depressions pale translucent brown to straw; T6 teeth pale brown.

Pubescence: [described from female from Valparaiso, MCZ-ENT 00731886]: Silver, appressed, obscuring integument only on lower paraocular area, genal area close to compound eye, most of mesopleuron and dorsolateral area of propodeum; sparser on clypeus, sparser and suberect on genal area posteriorly. Face with erect to suberect pale setae < 1.2 MOD, those of lower frontal area curved ventrally; pronotal collar and mesoscutum anteriorly with sparse, posteriorly oriented appressed setae; mesoscutum, scutellum, metanotum and mesopleuron with sparse erect setae < MOD. Metasomal terga and sterna with sparse short subappressed posteriorly oriented setae ≤ 0.4 MOD; suberect setae intermixed on terga < 0.5 MOD, these longer and denser on more posterior sterna, < MOD on S6.]

Surface sculpture [described from female from Valparaiso MCZ-ENT 00731886: Head, mesoscutum and mesoscutellum with minute punctures scattered in interspaces among large dense (mostly i ≤ d) areolate-punctate background; frontal area punctures denser, in rows with interspaces almost absent; upper paraocular area punctures smaller, irregularly spaced i < d; vertexal area punctate-reticulate; genal area with small punctures dense i < d sparser below, larger punctures scattered. Mesoscutum densely punctate i ≤ d except for a few larger interspaces posteriorly on disc, scutellum densely punctate i < d except punctures sparse on pale lateral portion. Mesopleural punctures coarse i < d except posterior glabrous portion with few scattered punctures restricted to ventral half and a subvertical row anterior to meso-metapleural suture; metapleuron with few short horizontal carinae posterodorsally; side of propodeum posterodorsally with irregularly sized shallow punctures among costae; metapostnotum horizontal portion longitudinally carinate-rugose with numerous faint transverse striae between carinae, areolate posterodorsally. Metasomal terga doubly punctate, minute punctures abundant; large coarse punctures dense i ≤ 2d on T1, i ≤ 4d on T2; T3–T6 punctures increasingly dense, i < 1.5d on T5, T6 areolate-punctate; S2 minute punctures sparse and obscure, larger punctures i = 0.5–2d; S3–S5 minute punctures distinct, larger punctures mostly i ≤ 1.5d; S6 i < d somewhat sparser along midline.]

Structure. Head ~1.3 × as wide as long, 83:60; [labrum transverse, narrowly oval, ~3 × as wide as medial length, W:L 41:14, aboral surface somewhat and apical margin conspicuously concave;] clypeus more than 2.5 × as wide as medial length, 63:24, lip ~half as wide as maximum width of clypeus 32:64; supraclypeal area median length one-quarter that of clypeus, 6; AOD 1.5 × maximum width of F1 (18:12); supra-antennal area with a complete somewhat dorsolaterally oriented lamella at lower third and several similarly oriented carinae above it and a few smaller ones below, area longer than maximum width 35:26, shorter than scape 37; frontal depression continuing above to somewhat below lower tangent of median ocellus; inner margin of compound eyes markedly convergent below UOD:LOD:MINOD 64:45:33; IOD = OOD; scape less than twice as long as greatest width (37:20); pedicel length = width; F1 ~2 × as long as greatest width 25:12; F2 ~1.5 × as long as greatest width 24:14, [remaining flagellomeres longer than wide, decreasing in length from F3 to F9, F10 longer L:W 22:16]; pronotal collar shorter medially than MOD, 15:19; [admedian line more than half medial length of mesoscutum], scutellum not depressed medially but with large posteromedial pit; length of scutellum:metanotum:metapostnotum 40:18:23. T6 somewhat triangular, sides slightly less than right angular to each other, with five teeth on each side, two apicomedial teeth the longest with length and basal width subequal, separated by somewhat more than their length. S2–S4 apical sternal depressions < 0.25 MOD, narrower medially, absent medially on S5.

Male: based upon the specimen from Cerros de Tiltil (MCZ-ENT 00731881), this specimen bears a minute red label devoid of script. (Fig. 11).

Figures 10–11. 

Cresson parvispinosus specimens used in the redescription of the species 10 lectotype female 11 male from Cerros de Tiltil (MCZ–ENT 00731881). Scale bars: 1.0 mm.

Dimensions Body length 4.93 mm, head width 1.47 mm, forewing length 3.45 mm, ITW 0.8 mm.

Colouration: Black except as follows: cream to pale yellow on basal two-thirds of mandible (rest orange to red-brown), clypeus (except lip orange-brown), supraclypeal area, lower paraocular area mark narrowly extending along inner eye margin to 1 MOD below lower tangent of median ocellus, small spot on genal area above adjacent to compound eye, ventral half of scape, small spot on pedicel, large lateral marks on pronotal collar twice as wide as space that separates them, pronotal lobe (margined with orange-brown dorsally), large lateral spot on scutellum, most of propodeal spine, mark in front of mesocoxa as large as ventral surface of mesocoxa, most of ventral surfaces of all coxae, most of ventral surface of profemur, dorsal surface of pro- and mesotibiae extending onto posterior surfaces apically, narrow ventral stripe on apical half of mesofemur, most of anterior surface of metatibia, anterior surfaces of all basitarsi (rest of metatibia and maining tarsomeres orange to pale orange-brown), medially interrupted narrow subapical bands on T1–T6, most widely separated on T2 and most narrowly on T6. Following parts orange-red: T1 and T2, T3 apicolaterally; S2 (suffused with red-brown medially), S3–S5 subapical markings increasingly narrow on more apical sterna. Apical tergal and sternal depressions pale translucent orange-brown.

Pubescence: As in female except for S2–S5 with dense apicomedial setal fringes, setae long, medially 0.75 MOD.

Surface sculpture: As in female except as follows: micropunctures almost absent on face and mesoscutum; upper paraocular area more sparsely punctate i > d; vertexal area punctures variable in size; lateral surface of propodeum punctures among carinae deeper.

Structure: Head ~1.3 × as wide as long, 81:60; labrum transverse, narrowly oval, less than 2.5 × as wide as medial length, W:L 37:16, apical margin somewhat concave medially; clypeus ~2.5 × as wide as medial length, 69:27, lip almost half as wide as whole clypeus, 33:69; supraclypeal area minute, median length one-quarter as long as clypeus 7:27; AOD equal to maximum width of F1; supra-antennal area much longer than maximum width 31:18, shorter than scape 34; frontal depression poorly demarcated above; UOD:LOD:MINOD 60:40: 29; IOD greater than OOD 28:23; scape almost twice as long as greatest width 34:18; pedicel length subequal to width; F1 more than twice as long as greatest width 23:10; F2 less than twice as long as greatest width 20:12, remaining flagellomeres longer than wide, increasingly shorter from F3 to F10, F11 L:W 18:11, F11 somewhat falcate, ventral surface markedly concave. Pronotal collar shorter medially than MOD, 13:19; [admedian line more than half medial length of mesoscutum], scutellum narrowly impressed medially, with large posteromedial pit; length of scutellum:metanotum:metapostnotum 35:14:18. T7 somewhat semicircular with five apical teeth, median one shortest, submedian ones longest. Apical sternal depressions short; anterior angle of all medial interruptions of apical sternal depressions acute, posterior angles obtuse, less markedly so on more posterior sterna.

In both sexes there is variation in the colour of the propodeal spine, ranging from mostly semi-translucent white through cream to partially or entirely black. The extent of the pale subapical cream bands on the metasomal terga also varies: on T1 and T4 in females, T1 and T5 in males, the band may be interrupted medially or entire, it is always interrupted on T2–T3 in females and T2–T4 in males but may also be entire on T5 in females and T6 in males. The number of metasomal terga and sterna that are orange-red varies (Figs 12–16). For terga, both sexes always have T1 and T2 orange, both sexes sometimes have T3 entirely orange, but only in females does this sometimes extend to the entirety of T4. For the sterna, S2 is sometimes not entirely orange in both sexes, females sometimes have S2–S4 entirely orange, though in males only S2–S3 may be entirely orange (Fig. 16). Figures 15 and 16 show the relative frequency of the number of terga or sterna that are red separately for males and females. Clearly females, on average, have more extensive orange markings.

Figures 12–14. 

Metasomas of C. parvispinosus to show variation in colour 12 male with T1–T2 red 13 female with T1–T3 and sides of T4 red 14 female with T1–T2 and sides of T3 red. Scale bars: 1.0 mm.

The frontal depressions are often almost obscured by silvery setae and vary somewhat in extent sometimes reduced such that their dorsal margin is 1 MOD below the lower tangent of the medial ocellus. The mesoscutal punctation varies from being fairly uniformly dense i < 0.5d, to having quite a few interspaces at least as wide as the adjacent punctures especially on the posterior third.

Figure 15–16. 

Frequency histograms of different colour patterns of C. parvispinosus 15 for metasomal terga 16 for metasomal sterna. Females in grey, males in black.

In males: 1) The supraclypeal area varies from entirely whitish to entirely black with intermediate conditions of brown or dappled pale and dark (Figs 17–19). 2) There is variation in the extent of pale colouration on the antenna, pronotum and scutellum. Some individuals have pale spots on the ventral surface of the pedicel and F1 and F2, while others have these lacking or restricted to the pedicel. The colour of these markings also varies from pale cream to orange-brown. The markings on the pronotum and scutellum, while always present, vary somewhat in size.

Figures 17–19. 

Heads of male C. parvispinosus to show variation in colour of supraclypeal area 17 area entirely white 18 area entirely black 19 area dappled with asymmetrical white mark (white arrow). Scale bars: 1.0 mm.

In females the extent of the pale marking along the inner margin of the compound eye is variable: it is subequal in length to MOD in the lectotype but may extend more narrowly to below the upper tangent of the supra-antennal area. There is minor variation in the extent of yellow-brown on the scape and of pale colouration on the clypeus, pronotum and scutellum.

Two males (MCZ-ENT 00731882) have an additional cross-vein towards the apex of the second discoidal cell. This can be seen in figure 11 as forming a wishbone shaped outline that is almost a mirror image of the second submarginal cell on either side of the median vein. In the second specimen the additional cell is much smaller. There is variation in the size of the second submarginal cell such that the petiole can be almost absent to extending for more than two-thirds the distance between the marginal and second discoidal cells. One female has the right forewing with an additional vein that separates off a small quadrate cell towards the distal extremity of the second submarginal cell. Another has this additional vein incomplete, and on the left wing. One male from El Pangue has the second submarginal cell sufficiently reduced it is almost circular with a diameter of less than three vein widths.

The two sexes average sizes are very similar; for the head width for the large sample from Region III females average 2.32 mm, SD. 0.215, n = 33, maximum 2.77 mm, minimum 1.82 mm; males average 2.33 mm, SD 0.16, n = 28, maximum 2.65 mm, minimum 2.03 mm. The series from the MCZ contains some smaller specimens: the smallest male has a head width of 1.45 mm, and the smallest female 1.48 mm. The smallest of all males available, the individual from El Pangue noted above, has a head width of 1.3mm.

There has been confusion over the nature of the type material of this species. Reed (1894) described a female specimen: his description starts with the female symbol. This is confirmed by the statement that the clypeus is pale marked on either side “una punta en cada lado del marjin anterior del clípeo …. amarillo blanquizco”; the male, in contrast, has an entirely pale clypeus. However, at the end of the description he implies that he has seen only two males, both from Colchagua “[H]e encontrado dos ejemplares, machos, de esta especie en Colchagua”. This is the only statement made about the provenance of any material of this species he studied. In the material from MCZ there is a single specimen from Colchagua and it is the only specimen bearing a red “type” label (Fig. 20). Seemingly confirming Reed’s confusion over the gender of the material he described, it bears a label stating that it is a male (Fig. 20). Consequently, I designate this specimen, which is a female, as the lectotype. As no other specimen from Colchagua is among the MCZ material, no paralectotype is designated at this time. Indeed, as none of the remaining MCZ material was available to Reed at the time of his publication (1894), they cannot be considered as syntypes. Pate (1938) was correct in noting that the “type” was a female, but implied that Reed had also described a male even though none of the males he listed had been collected prior to 1919, 25 years after Reed’s publication.

Figure 20. 

Labels from the lectotype of C. parvispinosus.

The lectotype female (Fig. 10) is in reasonably good condition, albeit with some apparent damage from mould with dried mycelia obscuring some features and it is missing the following parts: left antenna, right antenna beyond F4, left tegula, left mesotarsus beyond the 3^rd tarsomere, entire left metatarsus, right metatarsus beyond 2^nd tarsomere. Its condition necessitated some parts of the redescription to be made from a different specimen; the MCZ specimen from Valparaíso: MCZ-ENT 00731885 being chosen for this purpose.

Additional records for specimens not examined in this study but cited by Pate (1938) are as follows: Chile • 1 ♂; Valparaiso Province [Region V], Valparaiso; 25.xii.1919; P. Herbst; • 1 ♂, 1 ♀; Limache; [-33.0 -71.3]; 31.i.[no year]; A. Faz; AMNH; • 2 ♂ same collector as previous; CUIC.

Pate (1938) listed a female specimen from the MCZ with the locality “VALPARAISO PROVINCE, Concepcion, 4. Dec. 1910”, I believe that Pate misread the label, as it actually states “Concon”, with the gender of the specimen and date of its collection being the same, this specimen is listed in the material examined section above. Concon is just north of Valparaiso, there is no location known as “Concepcion” in Chile’s Region V (Ugarte, pers. comm.). The well known Chilean Concepción [Concepción de la Madre Santissima de la Luz] is the capital of Region VIII.

The type species of the genus is known from low altitudes in Central Chile, from 28°S in Region III in the north to ~38.7°S in Region IX in the south, Santiago to the east and Valparaiso and near Temuco to the west (Fig. 21). Despite our having collected extensively around Santiago and in the area between Santiago and Valparaiso, we have found no specimens of C. parvispinosus here. This area has been severely impacted by agricultural intensification since the time of the earlier collections of this species, but there remain large areas of good quality habitat especially in the more rugged areas, such as around Til-til (where we have collected frequently). Instead, most of our material comes from the southern Atacama Desert, over 500 km further north than the previous most northerly record for the species. Despite the distance and more arid habitat, it seems clear that the populations are conspecific, in that extensive study failed to reveal any consistent morphological differences among specimens from Region III and those from Regions V, VI, VII, IX and Metropolitana.

Figure 21. 

Distribution map of all records of Cresson spp. Red symbols: C. parvispinosus, star: the type locality for C. parvispinosus; blue: C. mariastea; green: C. salitrera. Scale bar: 500 km.

The Los Sapos locality where large numbers of C. parvispinosus were collected was a small, vegetated patch situated within a large area that was very dry and otherwise devoid of greenery over the time the samples were collected. It seems that roadwork immediately adjacent to the site had resulted in concentration of runoff in a small area (see fig. 30 in Mir Sharifi et al. 2018). Considerable numbers of bees and wasps were collected in traps (mostly bright blue) left out here for a few days and these included putative hosts for this cleptoparasitic nyssonine. The most likely hosts are among the following species for which large numbers of individuals were collected in the same traps as C. parvispinosus: two species of Tachysphex, identified using Pulawski (1974) as T. rufitarsis (Spinola) and a species perhaps allied to T. reedi Menke and two undescribed species of Parapiagetia Kohl.

9 ♀, 9 ♂ (several males missing apical metasomal segments): Holotype: ♀; Chile, Region I, 73 km E. Pozo Almonte; -20.312 -69.129; 3150m; 16.–21.iv.2012; pan trap; L. Packer; MNHN. Paratypes: • 6 ♂,7 ♀ paratypes identical data to previous; CAS, MNHN, PCYU, UCDC; • 1 ♂, 1 ♀paratype; identical data to previous; 10.v.2012; net; PCYU; • 1 ♂ paratype; identical data to previous; 21.iv.–10.v.2012; PCYU.

This species, as well as the following new species, is most readily distinguished from C. parvispinosus by the reduced areas of red on the metasomal terga (Figs 22–24); T2 with at least a broad medial black band for the entire length of the tergum (Figs 23–24) and usually mostly black, sometimes entirely so other than for the subapical cream band, most of T1 is also black whereas C. parvispinosus has T1 and T2 entirely red (Figs 12–14), with at most the extreme base of the anterior declivitous surface of T1 black and T2 with at most a small apicomedial dark mark (in one male). Females can be differentiated from those of C. salitrera Packer sp.nov described below by the structure of T6. In C. mariastea the apicomedial spines are relatively long, subequal to, to longer than, the space that separates them (compare Figs 25 and 26), the lateral spines are usually less numerous, most commonly with 4 in C. mariastea (range 2 to 6) and 6 in C. salitrera (range 4 to 7) and they are also relatively shorter, less sharp and extend less than half the way up the side of the postgradular portion of the tergum as opposed to ~three-fifths the distance in C. salitrera. In males, the easiest distinguishing feature is the degree of curvature of the apical flagellomere. In C. mariastea the ventral surface towards the apex is at an angle of ~40° to the long axis of the flagellum, while this is ~80° in C. salitrera (compare Figs 27 and 28). There are also differences in surface sculpture between the two species, most clearly shown in the basal depressed area of T2 in both sexes which has large, distinct, deep and dense (i < d) punctures in C. mariastea (Fig. 29) but minute, sparse (i > 5d) punctures in C. salitrera (Fig. 30) which are largely imperceptible with the light microscope.

Figures 22–24. 

Cresson mariastea 22 a paratype female, lateral view 23 holotype female, dorsal metasoma 24 male, dorsal metasoma. Scale bars: 1.0 mm.

Figures 25–30. 

Characters used to differentiate C. mariastea and C. salitrera 25 T6 of female C. mariastea, 26 T6 of female C. salitrera. Scale bars: 0.5 mm. 27 F11 of male C. mariastea 28 F11 of male C. salitrera. Scale bars: 0.25 mm. 29 base of T2 C. mariastea 30 base of T2 of C. salitrera. Scale bars: 100 µm.

Holotype Female (Fig. 22)

Dimensions: Body length 7.3 mm, forewing length 5.1 mm, head width 2.15 mm, ITW 1.3 mm.

Colouration: Black, following parts white to pale yellowish: mandible (except apical half increasingly dark towards apex, yellowish at midlength, red-brown at apex), labrum, lateral one-quarter of clypeus, narrow club-shaped mark on upper paraocular area adjacent to inner margin of compound eye extending from above upper tangent of antennal socket to below level of lower tangent of median ocellus, small mark on genal area above adjacent to posterior margin of compound eye, small mark towards side of pronotal collar separated by more than twice the width of the mark, pronotal lobe (margined with black above), small anterolateral mark on scutellum, triangular mark on mesopleuron anterior to mesocoxa, apical mark on all coxae (most extensive on mesocoxa where it occupies the outer third of the ventral surface), apicoventralless than two-thirds of profemur, anterodorsal surface of all tibiae (mostly pale yellow on pro- and mesotibiae, mostly white on metatibia), transverse subapical bands on T1–T5, entire only on T5, most broadly interrupted on T2, the interruptions are orange to orange-brown and narrower than the adjacent white bands. Scape yellow-orange apicoventrally. Following parts orange to orange-brown: torulus, all tarsi (probasitarsus suffused with yellowish, successive tarsomeres increasingly darker), posterior surface of metatibia entirely towards base, narrowing apically to absent at extreme apex; T1 and T3 narrow anterior margin to subapical pale transverse band, substantially broadened laterally on T1; T2 broadly towards side. Apical tergal and sternal depressions translucent straw laterally, orange-brown medially; T6 spines translucent orange-brown. S2 red brown, orange-brown towards margins; S3–S5 dark brown except red-brown towards apices.

Pubescence: Silver appressed and obscuring, or almost obscuring, underlying integument on lower paraocular area, genal area adjacent to compound eye, mesopleuron (sparser anteriorly and ventrally, absent posteriorly), scutellum posteriorly and dorsolateral portion of propodeum; somewhat less dense on clypeus, pronotal collar, anterior half of horizontal portion of T1; suberect longer setae ~0.7 MOD on most of genal area; sparse erect long whitish setae ≤ MOD on upper face, posterolaterally on pronotum, mesopleuron; similar setae somewhat shorter on mesoscutum and scutellum. Metasomal terga with short subappressed posteriorly oriented setae with sparse suberect setae intermixed, longest on T6, 0.3 MOD ; short setae

Surface sculpture: Micropunctures very sparse on head and thorax except on vertexal and genal areas, abundant on metasomal terga and sterna; punctation mostly coarse and dense, almost crowded on face with interspaces raised among linear groups of punctures; genal area with dense small punctures i < d among irregularly spaced large ones, surface uneven somewhat rugose posteriorly. Mesoscutum densely punctate i < d except posteriorly on disc i ≤ 2d; punctures of scutellum as on upper face except sparser laterally; metapostnotum longitudinally rugoso-striate on horizontal portion, areolate posteriorly. Larger punctures of terga mostly dense i < d with some sparser areas laterally on T1 and towards apex of T2 and T3; basal depressed area of T2 deeply, coarsely and densely punctate i < d; sculpture of T6 similar to that of face; sterna punctures dense towards sides i < d, less regularly spaced medially, i = 1–4d on S2, mostly i < 2d on S3–S5, i < d on S6 except midline largely impunctate.

Structure: Head almost 1.5 × as wide as long, 89:61; [labrum transverse, narrowly oval, three times as wide as medial length, W:L 36:12 apical margin transverse] ; clypeus almost 3 × as wide as medial length, 61:21, lip almost half as wide as clypeus, 28; supraclypeal area minute, median length third as long as clypeus; AOD 1.7 × maximum width of F1 (17:10); supra-antennal area longer than maximum width 27:20, shorter than scape 32; frontal depression poorly defined dorsally; UOD:LOD:MINOD 66:47:35; IOD:OOD 27:25; scape twice as long as greatest width 32:16; pedicel shorter than wide 11:13; F1 more than twice as long as greatest width 22:10; F2 less than twice as long as greatest width 22:12, remaining flagellomeres decreasing in length from F3 to F9 (F9 L = W), F10 18:12; pronotal collar approximately 0.5 MOD medially, 10:19; [admedian line distinct anteriorly for less than half medial length of mesoscutum], scutellum with faint medial line with large shallow depression posteromedially; length of scutellum:metanotum:metapostnotum 39:15:30. T6 triangular, sides forming an angle of ~60°, with three acute teeth on each side, restricted to less than apical one-third of side of tergum, two apicomedial teeth longer than their basal width 7:5, separated by a distance subequal to their basal width. S2–S5 apical depressions ~0.3 MOD , narrowed medially, abruptly so on S4–S5.

Male. Dimensions: Body length 6.6 mm; forewing length 4.1 mm; head width 1.75 mm; intertegular width 1.1 mm.

Colouration: Black, following parts white to pale yellowish: mandible basal third (mid third orange, apical third red-brown), labrum, clypeus, supraclypeal area, paraocular area completely filling space between antennal socket and compound eye below, extending narrowly along eye margin above to just below lower tangent of median ocellus, small oval mark on genal area above behind compound eye, ventral surface of scape, ventral spot on pedicel, pair of small spots on pronotal collar separated by more than 2 MOD and < 0.2 × the space that separates them, pronotal lobe (margined with black), large mark anterior to mesocoxa approximately equal in area to ventral surface of mesocoxa, ventral surface of all coxae except at base, ventral surface of profemur except basal fifth, apicodorsal mark on pro- and mesofemora, dorsal and most of posterior surfaces of pro- and mesotibiae, most of anterior surface of metatibia (posterior surface orange basally, orange-brown apically, blackish ventrally), anterior surface of all basitarsi and most of anterior surface of all second tarsomeres (remaining tarsomeres red brown), transverse subapical bands on T1–T6, very narrowly interrupted medially on T1, T4 and T5, more broadly interrupted on T2 and T3, complete on T6; S2 subapical band broad, S3 band narrow, S4 with small faint pale subapical mark. Pale marking on T1 narrowly margined with orange-brown, T2 with lateral orange brown spot anterior to pale band. Apical tergal; depressions translucent, largely colourless except orange-brown medially, apical sternal depressions pale straw except on S5 yellowish.

Pubescence: Silver appressed and obscuring, or almost obscuring, underlying integument on clypeus, lower paraocular area, frontal depressions, mesopleuron, metanotum posterolaterally, dorsolateral area of propodeum; somewhat sparser on genal area, pronotal collar, laterally on pronotum, anteromedially on mesoscutum, posterolaterally on scutellum, metanotum, most of horizontal surface of T1, anterior depressed area of T2. Longer, < 1.5 MOD , erect whitish setae on frontal and vertexal areas, mesoscutum and scutellum; similar setae somewhat shorter and sparser on mesopleuron; metasomal terga with sparse suberect setae posteriorly on T4–T7, longest on T7 < 0.5 MOD . Mesobasitarsal fringe setae < 1.3 × as long as greatest width of mesobasitarsus. S2–S5 apicomedial setal fringe ~0.7 MOD in length medially.

Surface sculpture: As in female except as follows: Micropunctures absent on head and thorax, abundant on metasomal terga and sterna; genal area densely punctate, vertexal area and scutellum rugoso-punctate, mesoscutum more sparsely punctate posteriorly on disc, i ≤ 3d; lateral surface of propodeum somewhat rugulose below propodeal spine. Larger punctures of S2 denser i ≤ 2d; S6 sparsely punctate except anterolaterally i ≤ d.

Stucture: Head ~1.4 × as wide as long, 86:62: labrum transverse, narrowly oval, almost 3 × as wide as medial length, W:L 35:13, apical margin transverse; clypeus less than 3 × as wide as medial length, 61:22, supraclypeal area almost entirely obscured by frontal crest in frontal view, only extreme lower margin visible medially; AOD slightly greater than maximum width of F1, 12:10; supra-antennal area longer than maximum width 28:20, shorter than scape 31; frontal depression extending to < 0.5 MOD below lower tangent of median ocellus; UOD:LOD:MINOD 55:38:26; IOD greater than OOD 23:16; scape more than 1.5 × as long as greatest width (31:18); pedicel length subequal to width; F1 twice as long as greatest width 20:10; F2 ~1.5 × as long as greatest width 19:12, remaining flagellomeres longer than wide, increasingly shorter from F3 to F10, F11 L:W 23:11, F11 somewhat falcate, ventral surface concave, apicoventral surface at ~40° to longitudinal axis of flagellum; pronotal collar approximately 0.5 MOD , 11:20; admedian line distinct anteriorly, obscure posteriorly, posteromedial scutellar pit obscure; length of scutellum:metanotum:metapostnotum 33:13:23. T7 somewhat semicircular with five narrow apical teeth, the median one shortest, the others subequal in length. Apical sternal depressions long, on S2 longer than the diameter of the largest punctures on the sternum; anterior and posterior medial angles of apical sternal depressions acute and obtuse, respectively on S2–S3, both approximately right angular on S4–S5.

The extent of red colouration on the metasoma varies, four males have the red restricted to a narrow line immediately anterior to the apical whitish tergal bands on T1 and T2 (as in Fig. 24), four have the mark on T2 expanded into a lateral patch and one has even more extensive red marks quite similar to the male imaged for the following species (Fig. 33). Five females have an expanded lateral red mark on T2 and the anterior edge of the white mark on T1 margined with red while four have large lateral marks on T1 and T2 (as in Fig. 23). Some specimens have more broadly interrupted tergal bands on T2–T4. Two female paratypes have whitish subapical transverse bands on S2 and one has such marks also on S3. Females vary in the size of the lateral pale mark on the scutellum from absent to extending for approximately half the length of the lateral margin. One male paratype has the pale spots on the pronotal collar extensive, almost as wide as the space that separates them, while three of them have these marks entirely absent. One male has a small pale lateral mark on the scutellum. One male lacks the pale mark on the pedicel while two also have pale marks ventrally on F1 and F2. The larger males have the lateral surface of the propodeum with dorsolaterally oriented carinae above as in the female. One male has the petiole of the second submarginal cell duplicated on one side, forming an additional, small, quadrate cell anterior to the normal second submarginal cell. One female has the petiole on the right forewing second submarginal cell almost absent.

Males vary in size from a head with of 1.6 to 2.02 mm; females vary in head width from 1.65 to 2.15 mm.

This species is named in honour of the late Maria Stea. During her too-short time at York University she was tireless in her efforts to assist the hymenopterists in the Biology Department.

All specimens of Cresson mariastea are from the mountainous area Northeast of the oasis town of Pica, and almost due South of Mamiña (less than 30 km from either) in an area known as the Pica Highlands (Fig. 21). This area has yielded many interesting species of Apoidea in recent years, including a new genus of fideliine (Praz and Packer 2017) and a new species of Colletes (Ferrari 2017) as well as its presumptive cleptoparasite, a recently described species of Isepeolus (Packer and Graham 2020).

An undescribed species of Parapiagetia and a species of Tachysphex I have not been able to identify were found simultaneously with C. mariastea and are its potential hosts.

7 ♀, 7♂. • Holotype: ♀; Chile, Region II, km 26.7, Rd. to Aguas Calientes (N. of Mina Vaquillas); -25.375 -69.288; 3350m; 31.x.2015–6.ii.2016; L. Packer, blue vane trap; MNHN. Paratypes: Chile • 1 ♀, 2 ♂ paratypes identical data as holotype; PCYU; • 1 ♂; Region II, Rd to Plato de Sopa, km 51.2; -25.379 -69.388; 3040m; 31.x.2015–6.ii.2016; L. Packer; yellow pan trap; PCYU; • 3 ♀, 1 ♂; CAS, PCYU; Region II, W. of Mina Vaquillas; -25.370 -69.372; 3130m; 31.x.2015–3.ii.2016; L. Packer; white pan trap; PCYU; • 1 ♂; Region II, S. of Cerro dos Hermanos; -25.404 -69.040; 4020m; 17.xi.–7.xii.2013; S. Monckton; PCYU.

Most readily distinguished from C. parvispinosus by the reduced areas of red on the metasomal terga (Figs 31–33), although usually not as reduced as in C. mariastea; T1 and T2 are at least black medially, although in one male only narrowly so. In contrast, C. parvispinosus has T1 and T2 entirely red, with at most the extreme base of the anterior declivitous surface of T1 black and T2 with a small apicomedial dark mark. Compared to C. mariastea, the apicomedial spines of T6 in the females are shorter, at most as long as their basal width, but the lateral spines are relatively longer and sharper (compare Figs 26 and 25). In both sexes the basal depressed area of T2 is minutely, sparsely punctate in C. salitrera (Fig. 30) but more coarsely and densely, i < d, punctate in C. mariastea (Fig. 29). The degree of curvature of F11 differs, in C. salitrera the ventral surface is at an angle of ~80° to the longitudinal axis of the flagellum (Fig. 28) while this is ~40° in C. mariastea (Fig. 27).

Figures 31–33. 

Cresson salitrera 31 male, lateral view 32 holotype female, dorsal metasoma 33 male, dorsal metasoma. Scale bars: 1.0 mm.

Holotype female (Figs 31–32)

Dimensions: Body length 7.1 mm, forewing length 5.1 mm, head width 2.18 mm, ITW 1.35 mm.

Colouration: Black, following parts white to pale yellowish: mandible basal one-third (rest red brown), labrum, lateral ¼ of clypeus, narrow club-shaped mark on upper paraocular area adjacent to inner margin of compound eye extending from upper tangent of supra-antennal area almost to dorsal tangent of frontal depression, small spot on genal area above adjacent to posterior margin of compound eye, transverse mark towards side of pronotal collar separated by slightly less than width of the mark, pronotal lobe (margined with black above, red–brown below), mark on scutellum occupying less than lateral one-quarter, posterior extremity of axilla, broadly divided transverse mark on mesopleuron anterior to mesocoxae, outer half of ventral surface of procoxa, outer half of mesocoxa, extreme apex of metacoxa, apicoventral and posterior two-thirds of profemur, anterodorsal surface of all tibiae (mostly pale yellow on pro- and mesotibiae, mostly white on metatibia), probasitarsus anteriorly, mesobasitarsus basal half; transverse subapical bands on T1–T5, entire on T1, T4 and T5, medial interruptions of T2–T3 blackish; narrow subapical bands on S2–S4 interrupted medially and incomplete laterally (replaced by orange-brown). Following parts orange to orange-brown: torulus, scape apicoventrally, most of posterior surface of metatibia (blackish ventrally), all remaining tarsomeres, T1 triangular marking anterior to subapical cream band broadest laterally, T2 lateral three-tenths red except anterior depression; apical tergal depressions pale straw to transparent.

Pubescence: Silver appressed and obscuring, or almost obscuring, underlying integument on lower paraocular area, frontal depressions, genal area adjacent to compound eye, mesopleuron, scutellum posterolateraly, metanotum except anteromedially and dorsolateral portion of propodeum; somewhat less dense on clypeus, pronotal collar, anterior one eighth of mesoscutum, most of horizontal portion of T1; suberect longer whitish setae ~1.2 MOD on most of genal area and mespisternum; erect long whitish setae <~1.7 MOD on upper face; short < 0.5 MOD erect pale setae on dorsal surface of mesocosm and T4–T6, similar setae shorter on T1–T3 and metasomal sterna with a few longer setae subapically ≤ 0.7 MOD .

Surface sculpture: Micropunctures absent on face except on vertex, sparse on mesoscutum and scutellum, abundant on metasomal terga, sparse on sterna and dense, i < d on genal area; punctation mostly coarse and dense, almost crowded on face with interspaces raised among linear groups of punctures, appearing almost striate, striae radiating from ocellar area; genal area larger punctures irregularly spaced i = 0.2–4d. Mesoscutum densely punctate i < d except posteriorly on disc i ≤ 2d; scutellum punctures i < d; mesopleuron large punctures i < 2d, posteriorly almost impunctate, metapleuron lacking sculpture except for a few short longitudinal carinae posterodorsally; lateral surface of propodeum carinate for posterodorsal two-thirds. Larger punctures of T1 irregularly spaced i < 3d, on T2 i < 4d except with areas lacking large punctures posteromedially; basal depressed area of T2 with shallow, sparse minute punctures i > 5d; T3 i < 3d, T4–T5 i > 2d, T6 i < 0.5d; S2 i < 2d, S3 i < 1.5d, S4 i ≤ d, S5 i < 2d, S6 i < d except midline largely impunctate.

Structure: Head almost 1.5 × as wide as long, 89:61; labrum W:L 36:13 apical margin somewhat concave medially; clypeus W:L 62:23, lip less than half as wide as clypeus, 28, distinctly narrower medially than towards sides; supraclypeal area median length approximately one sixth as long as clypeus; AOD almost 1.5 × maximum width of F1 (15:11); supra-antennal area longer than maximum width 30:18, as long as scape; frontal depression extending to ~0.5 MOD below lower tangent of median ocellus above; UOD:LOD:MINOD 71:45:35; IOD = OOD; scape less than twice as long as greatest width (30:17); pedicel shorter than wide 11:13; F1 2.5 × as long as greatest width 25:10; F2 less than twice as long as greatest width 20:11, remaining flagellomeres increasingly shorter from F3 to F9 except F10 16:12; pronotal collar almost half as long medially as MOD, 10:18; admedian line complete, more distinct for anterior half, scutellum with irregular medial line and large shallow depression posteromedially; length of scutellum:metanotum:metapostnotum 41:15:23. T6 triangular, sides forming an angle of ~80°, with four (left) to five acute teeth (right) extending to midlength of side of tergum, two apical teeth short, equal in length to their basal width, 4:4, separated by a distance clearly greater than their length, 7.5. S2–S5 apical depressions ~0.5 MOD , somewhat narrower medially but not abruptly so.

Male (Fig. 33)

Dimensions: Body length 7.8 mm, forewing length 5.2 mm, head width 2.25 mm, ITW 1.42 mm.

Colouration: Black, following parts white to pale yellowish: mandible basal half (rest red-brown), labrum, clypeus, supraclypeal area, paraocular area completely filling space between antennal socket and eye below, extending narrowly along eye margin above to approximately 1 MOD below lower tangent of medial ocellus, tiny spot on genal area above behind compound eye, ventral surface of scape, ventral spot on pedicel, pair of small spots on pronotal collar separated by 2 × MOD , pronotal lobe (margined with black), large mark anterior to mesocoxa approximately equal in area to ventral surface of mesocoxa, ventral surface of procoxa, mesocoxa except base, apical two-thirds of ventral surface of metacoxa, ventral and much of posterior surface of profemur except basal one-quarter, apicodorsal mark on pro- and mesofemora, dorsal surface and apical one-third of anterior surface of pro- and mesotibiae, anterior surface of metatibia (posterior surface orange basally, orange-brown apically, blackish ventrally), anterior surface of all basitarsi, transverse subapical bands on T1–T6, narrowly interrupted medially on T1, T4 and T5, more broadly interrupted on T2 and T3, complete on T6; irregularly-shaped subapical mark on S2, S3 band narrow and interrupted medially, junction of disc and apical sternal depressions narrowly orange brown. Second tarsomere on all legs yellowish, increasingly dark on more apical tarsomeres to red brown on pretarsus. Posterior surface of metatibia orange. Pale marking on T1 margined with orange anteriorly, marking broad laterally, restricted to narrow line medially; T2 orange for more than lateral one-third width of tergum. S2 with large orange spot on each side. Apical tergal depressions translucent, somewhat orange medially, on T1, T2 and T6 pale straw, on T3–T5 colourless all somewhat orange medially, apical sternal depressions straw yellow except of S5 yellowish.

Pubescence: As in female except as follows: suberect longer whitish setae ~MOD on genal area above and sides of mesopleuron; ~1.7 MOD on genal area below and scutellum; shorter ~MOD erect pale setae on mesoscutum, short 0.5 MOD suberect setae on T2–T6 and metasomal sterna, similar setae shorter on T1.

Surface sculpture: As in female except as follows: micropunctures abundant on S2; lateral surface of propodeum carinate for dorsal ½. Larger punctures of T1–T3 i ≤ 4d, T4 i ≤ 3d, T5–T6 < 2d, T7 i < d, crowded towards apex. S2 and S5 i < 6d, S3–S4 i < 2d, S6 with scattered punctures i = 1–6d.

Structure: Head almost 1.5 × as wide as long, 93:64; [labrum W:L 32:14, apical margin shallowly concave;] clypeus more than 2.7 × as wide as medial length, 66:24, lip less than half clypeal width 29, slightly shorter medially than towards side; supraclypeal area entirely obscured by frontal crest in frontal view; supra-antennal area L:W 27:18, shorter than scape 31; AOD greater than maximum width of F1 13:11; frontal depression almost reaching lower tangent of median ocellus; UOD:LOD:MINOD 73:49:33; IOD:OOD 19:17; scape ~ 1.5 × as long as greatest width, 31:20; pedicel almost as long as maximum width 13:12; F1 2.5 × as long as greatest width 32:13; F2 shorter than F1, > 1.5 × as long as greatest width 28:16, remaining flagellomeres ~1.5 × as long as wide except F11 26:10, somewhat falcate, downcurved and narrowing from base to apex, apicoventral surface at ~80° to longitudinal axis of flagellum; pronotal collar more than 0.5 MOD medially, 12:20; admedian line impressed for anterior two-thirds; length of scutellum:metanotum:metapostnotum 42:16:29; scutellum posteromedial pit absent. T7 semicircular with five teeth, medial tooth the shortest and broadest, submedial teeth as long as lateral ones but broader. S2–S5 apical depressions broad submedially > 0.3 MOD on S2, longer than largest punctures on sternum, impunctate apical portion clearly longer than diameters of basal punctures. Apical sternal depressions long, on S2 longer than diameter of largest punctures on sternum; anterior and posterior angles of medial interruption of apical sternal depressions slightly acute and slightly obtuse, respectively on S2, both approximately right angular on S3–S5.

There is minor variation in the extent of pale marking in females, some lack the medial interruption to the pale marking in front of each mesocoxa or have the metacoxa narrowly pale medially on the ventral surface. All have the red markings on T1 and T2 completely interrupted by black medially although in one male the dark marks are narrowed to < 0.5 MOD on T2 and are dark brown.

The species is known only from moderate to high altitude in an area of the Atacama Desert that is famous for its sodium nitrate (chile saltpeter) mines. These “salitreras” give the species its name, which is a noun in apposition. These mines dotted the landscape, especially in the late 1890s and early 1900s; but are now abandoned, mostly indicated by ruins and/or just their cemeteries. The known localities for the species are all from the sides of roads that form networks among these abandoned mines in a part of the country that would otherwise be almost inaccessible.

Two unidentified species of Tachysphex and an undescribed species of Parapiagetia were found in association with this species; none of them seem to be the same as those found associated with the other species of Cresson treated above.

This species comes from the part of the Atacama Desert where the absolute desert (rainfall less than 10 mm/yr) gets furthest inland, almost to the border with Argentina. Other species of interest from this area include the wasps just mentioned and a recently described cuckoo bee, Melectoides desiccata Packer and Graham. The type locality was imaged by Packer and Graham (2020; Fig. 9). The Cerro dos Hermanos locality is even drier and inhospitable.