Ant larvae are generally not a hot topic. Most people don’t see them because they are hidden within the ant nest. When noticed, the young ants seem to be legless grubs passively laying around and waiting to be tended by the adult worker ants. Or are they? Let’s take a closer look at ant larvae.
Ant larvae vary in shape depending on the species of ant, but in general they are legless, plump and resemble a comma or crochet hook in shape. They have a distinct head capsule. Some are sleek,
whereas others have numerous hairs.
Larval movement:
Ant larvae are not completely inactive; they are capable of movement.
Some species of ant larvae have been shown to sway to attract the attention of passing workers in a behavior that has been described as begging.
Other species can even raise themselves off the ground. Take a look at Mark Moffett’s photograph of bulldog ant larvae begging.
If you disturb an ant colony under a rock, you can observe ant larvae alternately straightening and curling, which looks like they are throwing their heads back. Presumably they are trying to attract the attention of worker ants.
This clip is a series of photographs showing ant larvae throwing their heads back. Try to follow the larvae towards the center from slide to slide as they curl and straighten.
(Let me know if you can’t follow it and I’ll put up the stills.)
Ant larvae as child laborers:
Ant larvae do make active contributions to the colony. The weaver ants, for example, use their larvae to produce the silk needed to tie leaves together to form the nest structure.
Probably the most surprising aspect of ant larvae is that not only do worker ants bring them food, but the larvae are often sources of food themselves.
Having ultra-thin waists (petioles) makes it impossible for adult ants to move solids into their food-processing centers in the hind section of their bodies (gasters). Adult ants can only consume liquids.
Scientists have long known that the worker ants feed all solids to the larvae first for processing. The larvae were thought to chew up, swallow and pre-digest the food, and then regurgitate it back to the workers to distribute throughout the colony.
Recently, however, researchers have shown that in one species of bigheaded ants the workers actually place the food on the surface of the belly of the larvae in a special groove (larvae lay on their backs). The larvae spit out enzymes onto the food, basically drooling on themselves. After a few hours, the workers come back and pick up the slime that results, feeding some of it to the larvae and taking some for themselves. According to videos of the larvae processing bits of fruit fly, the larvae very rarely sip any of the gooey liquid while the food is dissolving; they wait patiently until the food is done and let the worker ants feed them.
Other species of ants resort to feeding on the larvae in various ways. Certain species of ant larvae have special structures that allow the workers to access the internal body fluids (hemolymph), a sort of pump or “tap.”
The so-called Dracula ants take things a step further. These rare ants get their name from the fact that they cut holes in the sides of the larvae and suck out hemolymph. Although this sounds pretty gruesome, the larvae survive having holes bitten into them and later become workers themselves.
Another odd behavior of this group is that the workers carry the larvae to their food and place them on it, rather than carrying the food to the larvae, as most other ants do. For example, instead of cutting up a caterpillar into chunks and carrying it into the nest to feed the larvae, Dracula ants carry the larvae out to the caterpillar. Once they have fed, the larvae become food themselves.
Given the evidence, you can’t help but to conclude that ant larvae are important members of the ant colony and not just passive babies waiting to become workers.
References:
Bruno Gobin (2005) Larval begging for food enhances reproductive options in the ponerine ant Gnamptogenys striatula. Animal Behaviour vol 69: 293-299
Keiichi Masuko (1986). Larval Hemolymph Feeding: A Nondestructive Parental Cannibalism in the Primitive Ant Amblyopone silvestrii Wheeler (Hymenoptera: Formicidae). Behavioral Ecology and Sociobiology, Vol. 19, No. 4: 249-255
Keiichi Masuko (1989). Larval Hemolymph Feeding in the Ant Leptanilla japonica by Use of a Specialized Duct Organ, the “Larval Hemolymph Tap” (Hymenoptera: Formicidae). Behavioral Ecology and Sociobiology, Vol. 24, No. 2: 127-132
Keiichi Masuko (2008). Larval stenocephaly related to specialized feeding in the ant genera Amblyopone, Leptanilla and Myrmecina (Hymenoptera: Formicidae). Arthropod Structure & Development Volume 37, Issue 2: 109-117
See more about Dracula ants at Myrmecos Blog
Young Ants in the Kitchen -Science News for Kids Summary based on D. L. Cassill, J. Butler, S. B. Vinson and D. E. Wheeler (2005). Cooperation during prey digestion between workers and larvae in the ant, Pheidole spadonia. Insectes Sociaux Volume 52, Number 4: 339-343.