January 13, 2014
Our scientists found another species of ant-decapitating fly in Glendale, Pseudacteon amuletum!
Pseudacteon amuletum. Photo credit: Phyllis Sun Here's an account of this tiny, yet impressive fly, by Lisa Gonzalez, one of our BioSCAN entomologists: "For those of you who missed Lila’s exciting account of the moment Dr. Brian Brown first spotted an ant-decapitating fly in one of our BioSCAN samples as it was being sorted in front of our visitors in the Nature Lab, please enjoy this post. As Lila so eloquently described, ant decapitating flies are tiny but mighty little phorid flies that lay their eggs inside of the bodies of, you guessed it, ants. Many of these specialized flies have been the focus of our Entomology Department’s research as conducted in other, more tropical locales, so it may come as a surprise to hear that we have these incredible phorids right here in L.A. These parasitoids (a term we use to describe organisms that eventually consume and kill their host) will not just lay an egg in any ant they come across, but instead target a particular species.
Pseudacteon californiensis. Photo credit: Kelsey Bailey For instance, Pseudacteon californiensis, the first ant decapitator to turn up in a BioSCAN sample, preferentially seeks out the native velvety tree ant, small ants with an orange thorax that nest beneath bark and in tree cavities. Some ant decapitating flies, like zombie hunters, “aim for the head,” but P. californiensis has been observed hovering over the abdomens of velvety tree ant workers where they appear to “lift” the abdominal segments to insert an egg into the host. The larvae must then travel towards the head, making their way through the occipital foramen (the very narrow opening containing the connective tissue between the thorax and head), to complete their development in the head capsule, which eventually is separated from the body by enzymes released by the developing maggot. Our second Pseudacteon discovery from the same site in Glendale is P. amuletum, named from the Latin word for amulet due to its distinct horseshoe shaped oviscape that is reminiscent of a charm or pendant. One may also infer a deeper meaning of the name beyond shape but also of function: amulets can protect, and this species of Pseudacteon is important as a form of biological control against fire ants. A close relative of P. amuletum has been used to help control the spread of the imported fire ant Solenopsis invicta due in part for its rate of parasitism, but mainly because of how it affects the ant’s behavior. Solenopsis ants assume a very strange position when they detect Pseudacteon flies by lifting up their bodies and tucking their abdomens under and forward into a “C” shape with the same incredible skill of a Cirque de Soleil contortionist. It is believed that this helps protect the abdomen from egg invasion, but the trade-off is reduced foraging by the ant, which puts it at a disadvantage in relation to other more industrious, less preoccupied ant species. In this way, Pseudacteon contributes to a reduced fire ant population, which is greatly appreciated by those who know the alarming pain of a fire ant sting." I don't know about any of you, but I can't wait to hear if we find a third species of ant decapitating fly. For breaking news on what they're finding in the other BioSCAN traps, check out their blog.