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Identifying Mated Female Walnut Husk Flies

When you are ready to examine your husk fly trap catches under a dissecting scope or hand lens, use the photos below to help identify gender and recognize eggs.

At the first appearance of gravid females in your traps, you have one week to spray before egg laying. This procedure is not used if you are using GF-120 bait because these sprays need to be applied as soon as flies are caught rather than waiting for the gravid females. Names link to more information on identification and management.

Click on photos to enlarge

Distinguishing male from female, walnut husk fly
Walnut husk flies
Identification tip: Distinguish females from males by looking at the legs: the first leg segment of the female walnut husk fly is yellow, while the male is dark.

Gravid female walnut husk fly
Identification tip: To determine if a female has mated, gently crush the abdomens of females with a pointed tool, and use a hand lens or dissecting microscope to look for tiny white eggs.

Small eggs of gravid female husk fly
Identification tip: In the photo above there are about 7 eggs squeezed from a female mated husk fly. These eggs resemble small grains of rice.

Statewide IPM Program, Agriculture and Natural Resources, University of California
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