Insects of terrestrial origin over Indian Ocean during north-east monsoon

Abstract

Airborne insects, carried by winds were trapped over the Indian Ocean (Latitude 14 degrees N to 4 degrees S; Longitude 60 degrees-76 degrees 34 minutes E), in the course of cruise 109, ORV Sagar Kanya (January 4-February 6, 1996). A total of 3,217 airborne insects belonging to 7 orders, 53 families and 194 species were collected from 57 sampling stations, over 33 days. Hemiptera was the order with the highest number of insects (1,450), followed by Diptera (1,111), Hymenoptera (510) and Coleoptera ((127). Trichoptera, Microlepidoptera and Neuroptera were represented by 16, 3 and 1 insects respectively. Seventeen families had five or more representatives. The insects varied from 0.4 to 9.5 mm in length (from tip of the head to the tip of the abdomen). Major families were Cccidomyiidae (Diptera, sub order Nematocera) with 576 specimens, Chermidae (Hemiptera, s.o. Homoptera) with 329 insects, Chironomidae (Diptera, s.o. Nematocera) with 312 specimens, Agaontidae (Hymenoptera) with 285 insects and Coreidae (Hemiptera, s.o. Heteroptera) with 226 specimens. The data were examined for alpha diversity as well as for possible correlations between various parameters like the diversity index, size and number of insects trapped on one hand and the distance of the nearest landmass in wind direction on the other. The insect size and number did show a negative correlation with the distance of the nearest landmass but alpha-diversity index did not show a clear correlation.