From Science:
Bug parents have it easy. Instead of suffering the starving cries of their babies like bird and mammal mommies do, new research indicates that insects merely need a whiff of their kids to gauge what little ones need. The new findings reveal a novel way for offspring to communicate hunger. Moms receiving odors from ill-fed babies immediately set to finding more food. Mothers gassed with sated-baby odors, on the other hand, slowed their food search.
More here.