Today I want to talk about a type of fly that to us is an annoying house guest, but to ants is a gruesome killing machine that eats their brains from the inside out! But wait! Some background information about the ants must come first.
Carpenter ants are important recyclers of course woody debris in temperate forest ecosystems. However, in many southern states carpenter ants are one of the biggest pests, effectively destroying any wooden structure. Carpenter ants are extremely difficult to get rid of because they build their nests in cryptic locations and they form satellite colonies of workers and older brood in warmer, drier locations away from the parent nest.
Liquid or dust insecticides sprayed directly on the colony is one effective way to get rid of these pests. In order to maintain protection these treatments must be reapplied around the entire wooden structure at regular intervals. However, there are increasing concerns about their continued use around buildings, especially homes.
One alternative approach to carpenter ant control that reduces human-insecticide-exposure is baiting one ant to eat insecticide-laced foods in hopes the ant will return home and infect the entire colony. Unfortunately, this method is not very effective because ant workers shift feeding preferences between sugars and proteins.
Another alternative is biological control. Attempts have been made to use microorganisms such as fungi and nematodes (round worms) to manage carpenter ants. However, ants are social creatures and workers inside the nest fastidiously groom each other to remove fungi. Furthermore, extremely infected workers are removed from the colony. In our lab we have to track ants to determine their behavior. To do this, each ant must be marked so that it can be identified. One graduate student decided to paint splotches on the ants in different patterns in order to tell them apart. Unfortunately, the ants were so good at grooming that they could actually chip away at the paint, effectively ruining the identification strategy.
In order for a biological pest control method to be successful, the agent of infection must be less passive and more able to attack workers as they forage or enter the colony. This realization led to several genera of Phorid flies being used for ant management programs in many southern states. Although these flies do not inflict massive casualties on the population, they can disrupt foraging and thereby stress colonies, which gives less aggressive native ants an advantage. (Remember in one of my previous posts I mentioned that different ant colonies often attack each other.)
The most interesting (and exciting) part of all of this is not that people’s homes and businesses can be saved from carpenter ants, no; it is the way these flies kill the ants. Some species of Apocephalus (flies) attack the heads of healthy Camponotus (ants) species. Other Apocephalus species are drawn to injured ant workers. For example, female Apocephalus attophilus flies will land and walk towards workers of Atta laevigatus (ant) and examine their size. If the size of the ant fits within a certain range, the fly will lay one egg in the thorax of the ant. Then, the larva will hatch and migrate toward the ant’s head where it will feed on the soft tissue inside. The fly larva releases an enzyme just prior to pupation that causes the ant’s head to fall off. The fly pupates within the decapitated ant head and emerges as a fully grown fly in 10-14 days.
Well there you have it: a fly that decapitates ants. When I started this passion blog I had no idea how I was going to write about ants each week. Now, more than half way through the semester, I realize that ants are more interesting than I had ever imagined. I am so happy that this blog allows me to share all of these ant facts that I have learned! Thank you Jenna, Eric, John and Dr. O’Hara for reading my blog each week even if you find ants and their parasites utterly repulsive (…because they kind of are).
Picture of an adorable baby fly emerging from a poor ant’s decapitated noggin:
P.S. I learned all this information from a paper written by Mark E. Mankowski and Jeffrey J. Morell titled, Incidence of Apocephalus horridus in colonies of Camponotus vicinus and the Effect of Antibiotic/Antimycotic Mixtures on Fly Emergence.
P.P.S this picture is from https://weirdimals.wordpress.com/2010/01/14/ant-decapitating-flies/