Bigeyed bug have piercing and sucking mouthparts which they use to kill their prey and feed on their body fluids. They occur in cotton crops in early and mid season and numbers are highest in cotton during flowering. The numbers of bigeyed bugs in cotton are reduced by insecticide sprays, rainfall, high temperature and humidity. Lack of food or prey also reduces their abundance. A related species, Germalus spp, is also occasionally found. It is similar in appearance but slightly larger. The two may be distinguished by colour. Geocoris is dark brown to black whereas Germalus is brown and green.

Identification: The huge eyes of the bigeyed bug provide easy identification. Bigeyed bugs range in length from 3-5mm and are grey to dark tan. The nymphs resemble the adults but are wingless and more robust.

Lifecycle: The cylindrical, white eggs are laid singly on terminals and under leaves. The eggs hatch after a week and the nymphs pass through 5 growth stages before becoming winged adults. All of these stages are predaceous. Total development time is around 30 days and adults can live for up to 2-3 months.

Habitat: Bigeyed bugs can be found in most crops and landscapes.
 
Targeted prey: This fast moving day-feeding species is an important predator of eggs of Helicoverpa and other species as well as a range of other soft-bodied insects such as whitefly and mites. Bigeyed bugs can survive on nectar and honeydew when prey is scarce.

“The Bigeyed bug is an important predator of eggs and a range of small soft-bodied insects such as whitefly and mites.” 3mm Photo: M. Dillon

 
“Bigeyed bug nymphs are small wingless and a brownish colour. Their large eyes provide easy identification.” 1mm Photo: C. Mares