Age determination of the glassy-winged sharpshooter, Homalodisca vitripennis, using wing pigmentation
A red pigment is contained in the wing veins of the glassy-winged sharpshooter, Homalodisca vitripennis (Hemiptera: Cicadellidae). This insect is the main vector of the plant-pathogenic bacterium Xylella fastidiosa Wells (Xanthomonadales: Xanthomonadaceae), the causal agent of Pierce's disease of grapevines. Over the course of the H. vitripennis lifespan, the red pigment darkens and eventually becomes brown/black in color. These pigments are believed to be pheomelanin and eumelanin, respectively. The age of H. vitripennis can be determined by calculating the amount of red pigment found in the wings by analyzing high resolution wing photographs with image analysis software. In this study, a standard curve for the age determination of H. vitripennis was developed using laboratory-reared insects of known ages varying from 1 to 60 days. The impact of three environmental conditions on these readings was also investigated and found to have little effect on the age determination, and could be easily accounted for. Finally, field collected insects from several Central Texas vineyards were successfully analyzed for age determination suggesting that the annually reported influx of H. vitripennis was composed almost entirely of older insects.