Biomorphometric characteristics of different types of sensilla detected on the antenna of Helicoverpa armigera by scanning electron microscopy

A morphometric study on H. armigera antenna showed four styles of sensilla, i.e., styloconica, chaetica, coeloconica, and trichodea, and their numbers were estimated. Sensilla trichodea detect inter and intraspecific communication signals and was the most numerous. They were divided into three types: type I, the longest, with a length of 34.04 +/- 3.16 mu m and about 2.16 to 2.42 mu m in diameter at its base; 2) type II, intermediate, with a length of 22.58 +/- 0.77 mu m and basal diameter of 1.8-2.52 mu m; 3) type III, the shortest sensilla trichodea, with a length of 7.62 +/- 0.4 mu m and a range in diameter similar to that of type II. The length of the female sensilla trichodea was longer than that of the male. The total number of sensilla trichodea was estimated to be 7520 on the antenna of the female, and 6831 on the male antenna. The lengths of the sensilla trichodea type land type III were significantly different on male (t=4.6881, P=0.0034) and female antenna (t=18.9852, P=0.0001). An estimation of the predicted surface area of the most numerous type I on sampled segments between the 12th and 20th segments from a female of H. armigera showed a surface area of 5 x 10(3) mu m(2) and a sensillar density of 38 sensilla/10(3) mu m(2). The fraction of sensilla-occupied surface area was 0.4 mu m(2). (C) Korean Society of Applied Entomology, Taiwan Entomological Society and Malaysian Plant Protection Society, 2012. Published by Elsevier B.V. All rights reserved.