Ant behavior: March 2013 Archives

Trophic eggs (Mark)



Hey, AntAnswerers!

So, I've been thinking a bit about the situation with trophic eggs in ants. It apparently seems a pretty common practice among ant queens to eat some of their unembryonated eggs. Fair enough.
What I don't understand is the energetics of this practice- calorie for calorie, wouldn't it be costing a queen more to produce these trophic eggs than she is gaining from eating them?
I could understand making the best of a bad situation (i.e., for other arthropods that overshoot the optimal number of offspring, cannibalism retrieves some of the calories from a previous, poor decision), but I'm not sure that kind of argument applies for ants. Any thoughts from you guys?

I am similarly confused about the energetics of dracula ants, for similar reasons (i.e., the food comes from within the "extended phenotype").

Many thanks!
-Mark


Dear Mark,

Typically, trophic eggs are unfertilized eggs laid by workers and used predominantly to feed larvae and queens but can also be fed to other workers. This type of resource sharing is similar to the regurgitation (trophallaxis) that occurs frequently between ants that you may be more familiar with.

Queens can also produce trophic eggs and new foundresses often use these to feed their young larvae. They certainly could eat these themselves and they may be useful as a way of storing food until it is needed, but most are fed to their offspring.

Also, larvae do sometimes cannibilize other larvae as you mention. This system of feeding larvae may or may not be optimal for the colony but it undoubtedly benefits the larval aggressors.

Dracula ants are incapable of consuming solid foods because their mouthparts are not built for chewing. The larvae, however, can consume and digest these foods, producing a resource rich hemolymph. Many ant colonies operate in this way, indirectly feeding on the digestive capabilities of the larvae. Dracula ants are special because the larvae do not have the ability to regurgitate nutrients and must, therefore, be bitten open by the workers. Larvae of most other species are perfectly capable of regurgitation so this complicated method of sharing resources is not necessary.

Great question!
Ben Rubin & the AntAsk Team

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