A gregarious larval parasitoid, Cotesia dictyoplocae (Watanabe) (Hymenoptera: Braconidae: Microgastrinae), is reported for the first time from the host Antheraea assamensis Helfer (Lepidoptera: Saturniidae) from Assam, India. This wasp is a gregarious larval parasitoid and produces on an average 30 cocoons per host larva. Parasitized larvae are easily identified by the aggregation of exposed yellowish white cocoons on the body. Larval parasitism in natural conditions was low. Removal of parasitized larvae by hand is suggested.
Antheraea assamensis Helfer (Lepidoptera: Saturniidae), commonly known as the Muga silkworm, is known from the Oriental and the Indo Australian regions (geographical range: India, Burma, and Sundaland). In India it is endemic to Assam and adjoining areas in northeastern India. Muga silkworm is known for its magnificent natural golden-colored silk and hence is of economic value. The Hymenoptera parasitoid complex of Antheraea species includes: Anastatus spp. (Eupelmidae); Apanteles angaleti Muesebeck (Braconidae); Brachymeria alternipes Walker, Brachymeria lasus Walker, Brachymeria lugubris Walker (Chalcididae); Eupelmus sp. (Eupelmidae); Neotoxeumorpha exoristae Narendran (Pteromalidae); Nesolynx thymus (Girault) (Eulophidae); Perilampus nesiotes Crawford (Perilampidae); Pimpla rufipes (Miller) (Ichneumonidae); Trichogramma spp. (Trichogrammatidae); Trichomalopsis apanteloctena (Crawford) (Pteromalidae); Xanthopimpla pedator (F.) (Ichneumonidae); and Zele albiditarsus Curtis (Braconidae ) (Noyes 2015; Yu et al. 2012). The following host-plant genera are recorded for A. assamensis: Cinnamomum, Laurus, Litsea, Persea (Lauraceae); Magnolia, Michelia (Magnoliaceae); Quercus (Fagaceae); Sarcostemma (Asclepiadaceae); and Symplocos (Symplocaceae) (Arora & Gupta 1979).
Recently, Cotesia dictyoplocae (Watanabe) (Hymenoptera: Braconidae) was fortuitously reared from A. assamensis in Assam, India, on the host plant Persea bombycina (King ex Hook. f.) Kosterm. (Lauraceae) (Fig. 1). Cotesia dictyoplocae was originally placed in the genus Apanteles and described from specimens reared from Dictyoploca japonica Butler (Lepidoptera: Saturniidae). This is the first report of C. dictyoplocae parasitizing larvae of A. assamensis in India. Previously, C. dictyoplocae was known from China, Japan, and Korea. Cotesia dictyoplocae is a gregarious larval parasitoid, and females lay on an average 30 eggs per host larva.
The parasitized larvae were collected from Jorhat, Kamrup (Gauhati), Sivasagar, and Lakhimpur districts in Assam on the host plant P. bombycina, commonly known as “Som”. Six females reared from a larva of A. assamensis on 14 May 2015 in Jorhat, Assam (specimen code: NBAIR/14515) were examined. A macro image of the parasitized larva was taken using a Nikon Coolpix L820 camera. Photographs of the wasps were taken using a stereozoom Leica M 205 microscope with a Leica DC 420 camera and using Automontage software (version 3.8). Abbreviations used: metasomal/abdominal tergites 1–3 (T1−T3). Voucher specimens were deposited in the ICAR-National Bureau of Agricultural Insect Resources (NBAIR), Bangalore, India.
Cotesia dictyoplocae belongs to the glomeratus-subgroup of the genus Cotesia and is characterized by the following features: outer side of hind coxa glossy with fine and disperse punctations; mesonotum punctate, notauli absent; scutellum smooth; antennae about as long as body; first tergite broadening posteriorly; head, mesosoma, and metasoma black; legs reddish yellow except: coxae black, hind femora at extreme apices, apical third of tibia, and tarsi dark brown.
This species is difficult to identify using the key to the Chinese Microgastrinae (Chen & Song 2004) and keys only to the glomeratussubgroup in Papp (1987); however, specimens could be identified using Watanabe (1940). The following combination of characters separates it from closely allied species: face with weak, median, longitudinal carina; propodeum reticulate-rugose, with strong median longitudinal carina from which arise oblique carinae directed upwards on each side; T1 widened at apex, about 2 times as long as wide at apex; T2 2.4 to 2.5 times wider at apex than median length; T2 shorter than T3, both reticulate-rugose; T3 rugosity confined to basal region.
Diagnosis—female (Figs. 2−7): Body size 2.87 to 3.00 mm (in profile). Body color black. Antennae dark brown; legs red testaceous; all coxae black; hind leg with upper trochanter, femora at extreme apices, apical third of tibia, and tarsi fuscous; basal ventrites of metasoma yellowish-red. Head with minute punctations, face with weak median longitudinal carina, posterior ocelli closer to each other than to eye. Antenna little longer than body. Mesosoma closely punctate, scutellum sparsely and shallowly punctate. Propodeum reticulate-rugose; strong median longitudinal carina present, from which oblique carinae run upwards on each side. Pterostigma length shorter than metacarp. First abscissa of radius slightly longer than pterostigma width and twice as long as intercubitus; recurrent veins slightly longer than intercubitus. Hind coxa minutely punctate; hind tibial spurs subequal, half the length of the metatarsus. First metasomal tergite widened at apex, twice as long as wide at apex, excavated at base, smooth and shiny at the excavated portion, remaining reticulate-rugose; T2 shorter than T3, reticulate-rugose, sulci wanting; third tergite with rugosity at basal region; second and following tergites with median longitudinal ridge. Ovipositor sheath short.
The parasitism observed was occasional in nature and appeared at the time not to warrant control measures. We thank the Indian Council of Agricultural Research (ICAR) for research facilities. Literature aid from Dicky Sick Ki Yu, Canada, is kindly acknowledged. We are also thankful to Umesh C. Goswami, Gauhati University, Assam.