Mononeuron duguetiae Fischer

Mononeuron may be distinguished from the remaining doryctine genera by having the following combination of features: frons excavated; occipital carina meeting hypostomal carina; propodeum with semicircular or subtriangular shaped basal median areas (Fig. 2C); fore wing vein r-m present (Fig. 3C); first subdiscal cell of fore wing open at apex (Fig. 3C); hind wing vein SC+R absent (Fig. 3D); hind wing vein cu-a absent or spectral (Fig. 3D); hind wing vein 1A incomplete (Fig. 3D); hind wing vein M+CU equal to or slightly greater than vein 1M (Fig. 3D); hind wing vein m-cu slightly curved toward wing apex or straight to wing margin but never angled toward wing base (Fig. 3D); hind coxa with a distinct baso-ventral tubercle; basal sternal plate of first metasomal tergum less than 0, 25 length of tergum; metasoma sculptured on first three terga (Fig. 2C); ovipositor apex strongly sclerotized and with a single nodus (Fig. 2D).

Mononueuron is morphologically similar to Allorhogas, but it can be distinguished from members of this genus by having the vertex at least partially striate (Fig. 2B) (coriaceous in all described species of Allorhogas); hind wing vein SC+R absent (present in all described species of Allorhogas except Allorhogas ingavera Marsh); hind wing vein cu-a absent or spectral (sclerotized or nebulose in most described species of Allorhogas, only spectral in Allorhogas argentinus Brèthes and Allorhogas shawi Marsh); hind wing vein 1A incomplete (always reaching vein cu-a in other described species of Allorhogas); ovipositor long, about 1.5 times length of metasoma (Fig. 3B) (generally shorter than metasoma in most of the described species of Allorhogas, longer than metasoma in Allorhogas gallicola Gahan).

Female. Colour: Body and first three flagellomeres honey yellow, remaining flagellomeres, fifth tarsomeres and ovipositor sheath light brown (Fig. 3B). Body length: 2.5 mm; ovipositor 2.5 mm. Head: Clypeus smooth, face and frons smooth, frons slightly excavated, vertex slightly striate laterally and anteriorly, smooth posteriorly (Fig. 2B), temple and gena smooth (Fig. 2A); eye 1.45 times higher than wide (lateral view); malar space 0.45 times eye height (lateral view); temple 0.46 times eye width (dorsal view); ocular-ocellar distance 3.3 times diameter of lateral ocellus; length of scape 1.4 times its width (frontal view); antenna with 20 flagellomeres. Mesosoma: Length of mesosoma 1.5 its maximum height; pronotum smooth laterally, pronotal collar short (Fig. 2A); pronotal groove weakly scrobiculate, propleuron smooth; mesoscutal lobes coriaceous; notauli shallow but distinct, obscured before scutellum at middle of mesoscutum in a costate-rugose area (Fig. 2B); scutellar disc slightly coriaceous; median length of scutellar sulcus 0.33 times median length of scutellar disc, with six carinae (Fig. 2B); mesopleuron coriaceous, weakly coriaceous medially (Fig. 2A); subalar groove scrobiculate; precoxal sulcus wide, smooth, 0.5 length of mesopleuron; venter of mesosoma slightly coriaceous; metapleuron strongly rugose; propodeum with a pentagonal areola diverging at the base of propodeum, areolar area rugose, basal median areas coriaceous (Fig. 2C). Wings: Fore wing length 2.75 times its maximum width, length of pterostigma 3.2 times its maximum width, vein r about 0.5 times length of vein 3RSa, vein 3RSb reaching the wing margin as a tubular vein; vein m-cu interstitial to vein 2RS, vein 1cu-a distinctly postfurcal with vein 1M (Fig. 3C); hind wing vein SC+R absent; vein cu-a absent (Fig. 3D); vein m-cu nebulous (Fig. 3D); vein 1A reduced, only present basally; vein M+CU about equal length of vein 1M (Fig. 3D). Legs: Fore tibia with a row of 12 spines; hind femur weakly coriaceous, length 3.86 times its maximum width; hind coxa weakly striate dorsally, coriaceous laterally, with a distinct basal tubercle. Metasoma: Length of first metasomal tergum 0.9 times its apical width, median area slightly coriaceous basally, costate-rugose apically, costate-rugose laterally, with complete longitudinal lateral carinae; dorsope present, acrosternite 0.2 times length of first metasomal median tergite; second metasomal median tergite longitudinally costate (Fig. 2C); third metasomal median tergite costate on basal half, smooth on apical half (Fig. 2C); remaining metasomal median tergites smooth; ovipositor 1.8 times length of metasoma. Ovipositor strongly sclerotized apically, with a single nodus (Fig. 2D).

Male. Slightly smaller than female. Body length 2.0–2.5 mm; hind femur swollen, length 2.35 times its maximum width.

Variation. Females: Antenna with 16–21 flagellomeres; scutellar sulcus with 5–6 carinae.

We collected 20 leaves of Duguetia furfuracea infested with galls at the type locality of Mononeuron duguetiae in February of 2011. All leaves were placed in a plastic bag and maintained at room temperature. Each of the collected leaves had between three to 10 spheroidal galls with a maximum diameter of approximately 1 cm (Fig. 3A). Twenty five specimens of Mononeuron duguetiae emerged from the galls a few days after being collected, and two or more individuals were observed to emerge from each gall. Moreover, two specimens of an unidentified cecydomiid species and the following wasp taxa emerged after most of the specimens of Mononeuron duguetiae had emerged: Torymidae (six specimens belonging to an unidentified species), Eurytomidae (13 specimens of an unidentified species assigned to Sycophila Walker, and eight specimens of an unidentified species), Eulophidae (21 individuals of an unidentified species), and Diapriidae (one unidentified specimen). Members of some of these wasp families are usually parasitoids (Torymidae, Eulophidae), whereas others are generally phytophagous (e.g. Eurytomidae). We could not confirm that Mononeuron duguetiae is the species that induces the above galls, though its early emergence suggests that it might be cecidogenic.

Comments. The genus Mononeuron has been mainly characterised by the absence of hind wing vein cu-a. This feature was employed to distinguish the genus in the key to New World doryctine genera provided by Marsh (1997). We found that some of the examined specimens of Mononeuron duguetiae have hind wing vein cu-a spectral (sensu Mason 1986) but present. Some described species of Allorhogas also have a nebulous or even spectral hind wing vein cu-a (e.g. Allorhogas argentinus, Allorhogas shawi; Marsh 2002).

In our Bayesian analysis, Mononeuron duguetiae was more closely related to Monitoriella and Labania than to the species of Allorhogas, although with marginally non- significant support. This contrasts with our morphological examinations, which show that there are various external morphological features in Mononeuron duguetiae shared with species of Allorhogas. The latter genus is a mainly Neotropical and Nearctic group with 33 described and an undetermined number of undescribed species. Among the features shared by Mononeuron duguetiae and members of Allorhogas are an excavated frons, hind wing vein r-m present, pronotal collar very short or absent, propodeum usually with semicircular or subtriangular shaped basal median areas, basal sternal plate of first metasomal tergum less than 0.25 length of tergum; metasoma sculptured on first three terga, hind coxa with small but distinct basal tubercle, fore wing vein r-m present, first subdiscal cell open at apex, and hind wing vein m-cu usually curved toward wing apex, often straight to wing margin but never angled toward wing base. Further molecular phylogenetic studies employing additional markers and more taxa, especially for the species of Allorhogas, will confirm the relationships of Mononeuron duguetiae with respect to other gall associated doryctine genera.

We also examined various specimens assigned to Mononeuron duguetiae deposited in the DCBU collection that show some morphological differences, and which might represent an undescribed species. These specimens were collected in the type locality of Mononeuron duguetiae and all of them were reared from the same type of galls on Duguetia furfuracea. They differ from our concept of Mononeuron duguetiae by having the vertex, mesopleuron and basal areas of propodeum mostly smooth, and the first metasomal median tergite smooth and with brown colour. Further molecular data will allow us to confirm whether this represents an undescribed species of Mononeuron or intraspecific variation within Mononeuron duguetiae.

Holotype (DCBU).–Female. Brazil, São Carlos, São Paulo, geschlüpft von Gallen von Duguetia furfuracea ST. HILL. (Annonaceae). Other examined material: 31 specimens, 12 males, 19 females. Twelve specimens: Brazil, SP, São Carlos, UFSCar, Cerrado forest, 21°58'7.96"S, 47°53'9.68"W, ex. Duguetia furfuracea galls, 26 January 2011, A. Zaldívar-Riverón and J. Nunes coll. Nineteen specimens: same locality as above, 18 March to11 April 2008, A. M. Penteado-Dias, coll.