Exorista mella

Physical characteristics include having a stigmal plate that is not elevated like their protuberance, as well as a sternopleuron pertaining to the thorax on the lateral side with three bristles. Likewise, behavioral characteristics include their parasitoid tendencies. As parasitoids, E. mella typically spend most of their life growing in a host. Unlike other fly species born in a host, in E. mella, neither sex determination nor sex ratio divergence is related to host size. However, the size of adult E. mella is directly correlated with the size of the host from which the fly emerged. Thus, flies that were oviposited and burrowed alone into larger hosts were larger than those that emerged from a smaller host or one that was superparasitized. Additionally, host larvae activity has a larger impact on parasite oviposition than host larvae size. == Distribution and habitat ==

E. mella is commonly found in the United States and in Canada. In Arizona, E. mella have been found in the mountainous regions as well as agricultural regions of southern Arizona. == Life cycle ==

Larvae On average, the larval development of E. mella lasts for 10 days. Larvae emerge from their eggs on the surface of their hosts, after which they burrow into the host for the remainder of their development. Pupae E. mella larvae are able to emerge from any stage (i.e. prepupae and pupae) of their host during their development. Longevity The lifespan of adult E. mella flies varies. Males typically have an average lifespan of about 29.5 days, while females survive an average of about 38.0 to 40.6 days. == Parental care ==

Preoviposition The earliest recorded viable eggs in a study were from females 48 to 72 hours old, which had immediately mated after emerging. Even without having mated, newly emerged females have also been documented to be able to oviposit infertile and consequently unviable eggs. The gestation period lasts for an average of at least 2 days upon emergence from the host. The most an E. mella fly has been recorded to oviposit on a single host for one study was 65 eggs. Typically, the oviposition period lasts for about 24.8 days. E. mella typically oviposit on the cuticle of their host, but have also been documented to oviposit on the head capsule, setae, prolegs, and on the abdomen of hosts. Though they prefer to oviposit on live hosts, females were also observed to oviposit on the surface of dead hosts. Larger females were also observed to oviposit a greater number of eggs than smaller females. == Parasitism ==

Hosts As a polyphagous and generalist fly, E. mella feeds on a variety of hosts. It has been recorded to parasitize the following families of caterpillars: Arctiidae, Noctuidae, Notodontidae, Lymantriidae, and Lasiocampidae. Some of these hosts, such as the Apantesis incorrupta moth, have been observed to be able to fight back against parasitism by E. mella through a particular diet of plants, as well as surviving through adulthood. == Mating ==

E. mella flies have been found to mate shortly after emerging from their host, and the success rate of mating increases when the time before the formation of pairs after emergence is shorter. Both sexes have been observed to show a decline in their ability to produce viable offspring after a certain amount of time after emergence. For males, this was on average 14 days, while for females it was after 16 days of emergence. Males have been observed to have the ability to fertilize the eggs of more than one female. Thus, it is the usual case that pairs mate shortly after emerging from the host. == References ==