First host record for the Palaeotropical braconine wasp genus Cassidibracon Quicke (Hymenoptera, Braconidae) with the description of a new species from India

A new species, Cassidibracon gracillariae Quicke sp. n. from India, is described and illustrated and differentiated from other Indian species. The three known specimens were each reared from distinctive, exposed, bubble-coated cocoons of the gracillariid moth Stomphastis chalybacma (Meyrick, 1908), which superficially resemble insect egg clusters. This is the first reported host record for the genus Cassidibracon Quicke.


Introduction
The Braconinae is one of the largest and most generically diverse subfamilies of braconid parasitic wasps with 177 genera and 2,442 species described up until 2005 (Yu et al. 2005). The vast majority of species for which biology is known are ectoparasitoids of concealed hosts, principally Lepidoptera and Coleoptera and less frequently, Dip-tera. A few taxa belonging to the Aspidobraconina have been know for a while to be endoparasitoids of butterfly pupae (van Achterberg 1984;Quicke 1987a) and possibly of Limacodidae prepupae (Austin 1987;van Achterberg 1989). However, in recent years, several species have been shown to have aberrant biologies including adult ant ectoparasitism (Yu and Quicke 1997), ant brood parasitism including egg predation (Quicke and Stanton 2005), or even seed predation (Flores et al. 2006), or, in the case of Pycnobraconoides Quicke, carrying a potential host around (Quicke and Marshall 2011). Therefore, it s not unlikely that other atypical biologies remain to be discovered.
During searching of the braconid accessions collection in the Natural History Museum, London, three 100 years old specimens of a small braconine were found, each mounted above a small leaflet with what superficially looked like a white eggmass. However, on closer examination, these white masses were found to be the distinctive bubble-like ornamentation of the cocoon of a gracillariid moth. The specimens were labelled as having been reared from Epicephala chalybacma, now treated as Stomphastis chalybacma (Meyrick, 1908) (Lepidoptera: Gracillariidae) which is recorded from India and is widespread in S. Asia.
The wasps were all rather dirty, and too fragile to attempt all but the most superficial of cleaning. Nevertheless, they were in sufficiently good condition to be described. The three possess a combination of characters used to describe a putatively monophyletic group of genera referred to as the Plesiobracon Cameron (1903) group as defined by van Achterberg (1983) -viz, scapus truncate and shorter ventrally than dorsally in lateral aspect, claws with a pointed basal lobe which is characteristic of members of the Braconini, a densely setose mesoscutum, fore wing veins 1-SR and C+SC+R forming an angle of >60°, propodeum with a complete midlongitudinal carina and strong and complete dorso-lateral carinae of the 1 st metasomal tergite.
In the key to the Plesiobracon group genera provided by Quicke (1988), they run with a bit of difficulty to Cassidibracon Quicke, which was originally described from Africa, but has since also been recorded from India (Narendran et al. 1994). Based on the descriptions the reared specimens here appear to represent a different species from the three known Indian species, and they are accordingly described as new. This provided the first host record for the genus Cassidibracon. Legs. Hind tibia robust, without disting longitudinal groove. Claws with small, acutely pointed basal lobes. Metasoma. Metasoma short and robust, with 5 exposed, coarsely sculptured tergites. 1 st tergite with spiracle approximately at midlength, with complete though somewhat irregular dorso-lateral carina behind spiracle, with dorsal carinae fused to form a semicircular transverse carina that runs far closer to posterior margin of tergite than its base. 2 nd +3 rd tergites large, their combined medial length more than 3 × length of exposed (coarsely sculptured) parts of tergites 4 and 5. 2 nd tergite without midbasal or anterolateral areas, with weak sublateral, posteriorly converging grooves on anterior 0.5 2 nd suture curved, narrow, crenulate. 3 rd tergite without anterolateral areas. Tergites without transverse subposterior grooves. Ovipositor short, sheaths approximately 1.2 × length of hind basitarsus.
Comments. Cassidibracon Quicke (1987b) belongs to the Plesiobracon Cameron (1903) group of genera as defined by van Achterberg (1983). It was originally described from the Afrotropical region (Sierra Leone) on the basis of three females and a male collected in seasonal woodland (Quicke 1987b). The type species C. castus Quicke has a distinct knob between the antennal sockets which is absent in the new species described here as well as in the three other the Indian species described by Narendran et al. (1994). The type specimens of the three oriental species described by Narendran et al. (1994), viz. C. indicus Narendran & Rema, C. malabaricus Narendran and C. sumodani Narendran & Madhavikutty are now deposited in the collection of the Termeszettudomanyi Muzeum Allattara, Budapest, Hungary (van Achterberg and Narendran 1997). Paratypes. 2 females, same data as holotype. Diagnosis. In Narendran et al.'s (1994) key to species, the new species runs to C. sumodani Narendran because of its complete propodeal carina, but differs in having more (24 as opposed to 21) flagellomeres and in the dark pattern on the metasoma. The new species differs from all other known species of the genus in having a large 'H'shaped black mark extending over tergites 2-4. Description. Length of body 2.9 mm, of forewing 2.6 mm and of antenna 2.8 mm.

Narendran et al.'s (1994) key can be modified as follows to include the new species.
Head. Antenna with 24 flagellomeres. Median flagellomeres approximately 1.4 × longer than wide. 1 st flagellomere 1.1 × longer than both the 2 nd and 3 rd segments separately. Face shiny with numerous punctures at bases of setae. Height of eye: width of head: width of face = 1.0: 2.5 : 1.05. Intertentorial distance 1.7 × tentorio-ocular distance. POL: transverse diameter of posterior ocellus: shortest distance between posterior ocellus and eye = 1: 1 : 3.
Coloration. Antenna orange-brown becoming black on apical third. Head creamyellow with stemmaticum black. Mesosoma largely cream-yellow with dark marks on lateral lobes and anterior of middle lobe of mesoscutum. Metasoma cream-coloured with large 'H'-shaped black mark extending over tergites 2-4.
Notes on biology. The type series of Cassidibracon gracillariae sp. n. are labelled as having been reared from 'E [picephala]. chalybacma' (now Stomphastis chalybacma (Meyrick, 1908)) (Lepidoptera: Gracillariidae). Specimens of S. chalybacma in BMNH share the highly distinctive cocoons and there is no doubt that the original host identification was correct. The host is a widespread moth in south-east Asia which mines leaves of Caesalpinia and Samanea species (Fabaceae). The gracillariid, which feeds solitarily as a leaf-miner, pupates in a flattened silken cocoon ornamented with a cluster of distinctive bubbles, excreted by the larva, along the whole length of the cocoon. These bubbles presumably serve a defensive (or camouflage) function and resemble an egg mass, or possibly a parasitoid cocoon mass. The ovipositing Cassidibracon presumably attacks either pre-pupal larva or pupal hosts.