Immature morphotaxonomy of Culicoides jacobsoni Macfie, Culicoides thurmanae Wirth and Hubert, and Culicoides oxystoma Kieffer (Diptera: Ceratopogonidae)

Morphotaxonomy of immature stages can resolve misidentification, proliferation of cryptic species, and timely and effective management of vector species of Culicoides Latreille (Diptera: Ceratopogonidae) at the onset of development. Among 84 valid Culicoides species reported from India, many are unknown to be immature, and some are partially described. Culicoides jacobsoni Macfie and Culicoides oxystoma Kieffer are two species considered to be proven vectors of the bluetongue virus. In the present investigation, Culicoides thurmanae Wirth and Hubert were first reported in India. The surface structures of eggs of C. jacobsoni and C. thurmanae are newly described and photomicrographed using Scanning Electron Microscopy (SEM). The gravid females were collected using a UV LED light trap and identified morphologically. The eggs were retrieved by dissecting their abdomens and processing them under SEM. Simultaneously, the laboratory-reared oviposited and hatched eggs of C. oxystoma are also described. The field-collected engorged females were transferred onto moistened cotton beds for oviposition. Embryonated eggs were then transferred into pre-prepared rearing plates consisting of cattle manure, yeast solution, and nutrient broth solution, allowing for successive egg hatching and rearing of larval instars. The larval instar differentiation and morphometric measurements of four larval instars were newly noted. This investigation also highlights pupal diagnoses across sexes.