Mar 14, 2012 – Enemies of Ants
QUESTION:
What insect lays or injects eggs into ants?
ANSWER:
The insect that you may be thinking of is a tiny fly in the family Phoridae. We deal with phorid flies all the time, as nuisance flies that breed inside structures wherever they can find wet, decaying organic material, such as in a filthy drain or under a slab where plumbing has broken. But, consistent with the amazing diversity of the insect world, some species of Phorid flies are parasites on other insects, and several species pick on the Red Imported Fire Ant (RIFA).
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What insect lays or injects eggs into ants?
ANSWER:
The insect that you may be thinking of is a tiny fly in the family Phoridae. We deal with phorid flies all the time, as nuisance flies that breed inside structures wherever they can find wet, decaying organic material, such as in a filthy drain or under a slab where plumbing has broken. But, consistent with the amazing diversity of the insect world, some species of Phorid flies are parasites on other insects, and several species pick on the Red Imported Fire Ant (RIFA).
The female flies hover over active, above ground RIFA until they decide on a specific victim, and then the fly darts down and in a fraction of a second she uses here harpoon-like ovipositor to jam an egg into the ant. This momentarily stuns the ant, but it recovers and joins its group. The larva of the fly then develops for about 10 days in the thorax of the ant, which still is active in its colony, and then the fly larva moves into the ant's head, kills the ant, and causes its head to fall off. The ant's head is such a hard capsule that the fly pupa within is protected. Now that the ant is dead and in pieces other ant workers in the colony will remove it and toss it outside on the garbage heap, where the fly within is able to emerge as the adult fly without being exposed to ants within the colony.
RIFA workers are well aware of these phorid flies, and when ants above ground detect the flies hovering over them it disrupts their normal foraging behavior so badly that they may pile on top of one another to escape the flies. This in turn may reduce the amount of food being returned to the RIFA colony and ultimately weaken that colony substantially. Phorid flies are being released as part of a biological control program for RIFA. While they do impact RIFA colonies the flies are not at this time considered to be so effective that they will eradicate or even substantially reduce the numbers of the ants.
Another parasite of ants was recently discovered in tropical rainforests in Central and South America, and this is a nematode that manages to infect many species of ants. The effect on the ant that has the nematodes living inside is to develop an enlarged and bright red abdomen, which appears to resemble a ripe fruit. This resemblance then appears to attract birds that feed on the ants in the belief they are eating fruit. The nematodes are later excreted in the feces of the birds and once again ingested by ants that feed on the materials in the bird feces. This remarkable cycle of parasite, and, bird, and ant again was only recognized in 2005, so once again we find there is so much still to be discovered in the insect world.
In North America we also know of many different kinds of insects that feed on the larvae of ants, but in a very sneaky way. They manage to live within the ant colony itself, somehow giving off pheromones that cause the ants to believe that this predator within is just one of their own, and the predator is not harmed and even may be fed by worker ants. Some of these predatory insects include tiny butterfly larvae and various kinds of beetles.
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