Chemosensors and ovipositing

[Junhyong Kim]

I'm sure that there are more experienced people who can tell you better, 
but in general getting eggs on demand is a pain in the neck. I don't 
know if anybody has isolated specific chemical cues, but they respond 
mostly to presence of appropriately appealing food. There are several 
egg laying medium described in Ashburner's Drosophila Lab Handbook. I 
just use Carolina's instant blue medium reconstituted with grape juice 
with a layer of yeast paste. They tend to lay mostly during dusk hours 
which you can manipulate with lighting conditions. And they will also 
tend to lay eggs on demand if they have been food stressed (try starving 
them overnight and then present them with food). However, some species 
just won't lay 'em no matter what you do. (I'm having horrible time with 
hydei spp.) OTOH, simulans spp. seems ready to lay eggs at anytime.

Junhyong Kim