Mallophora ruficauda

Researchers have shown that M. ruficauda antennae are involved in resource-searching behavior, in addition to detecting outside chemical cues that the flies are able to pick up on.[6] Their antennae are composed of four different segments: the scape, pedicel, postpedicel, and style. In addition, there are three separate types of sensory pits observed on the antennae.[6] Together, these morphological characteristics contribute to the odor detection mechanism found in adult M. ruficauda, which may be used in mate detection, habitat recognition, predator avoidance, and searching for food.[6]

Eggs are laid in aggregate clusters of approximately 300 on the tips of tall stalks of grass or wire fencing. Oviposition occurs at the optimal height for larval dispersal and location of hosts, which is about 1.25 to 1.5 meters above the ground.[7][4] These clusters are typically near adult food sources, such as beehives. Upon hatching, the tiny larvae drift to the ground, dispersing under wind power. This helps them spread out so that they do not all encounter and parasitize the same host, which would cause competition for resources between the larvae.[4] The larvae then begin to dig in an attempt to find a host (preferably a larval Cyclocephala signaticollis, a type of scarab beetle, though the larvae are not strict specialists and will parasitize several species of white grub),[8] which will be located by the chemical cues provided by its own abdominal excretions. The larvae take 7 days to molt in the soil and enter the second instar, at which point they can detect and orientate towards the chemical cues produced by the grubs, and they dig through the soil towards prospective hosts.[9] Upon finding a host, the larvae attach to the cuticle and begin to feed. The larvae stay attached to their hosts for the rest of the larval stage, eventually killing the host upon pupation. Larvae can survive through the second instar on their own, but if they do not find a host before the second instar ends, they will die.[10]

Superparasitism is common among the larvae of M. ruficauda, with many larvae sometimes infecting a single host. They prefer unparasitized hosts if they can find them in order to avoid competing with members of their own species. However, the hosts are randomly distributed in the soil and the larvae may all have to share a host if only one is available. The larvae can discriminate between unparasitized and already-parasitized hosts by chemical cues, and will preferentially crawl towards unparasitized grubs. As the size of a host increases, the likelihood and severity of superparasitism also increases (presumably because a larger host is capable of supporting more parasites). These findings are one of the first reports of host discrimination by larvae rather than by adults. It makes sense that a Dipteran species would evolve this ability, since Dipteran parasitoids rarely have a strong enough ovipositor to lay eggs directly in a host. This eliminates the ability of the mother to choose a good host for her offspring; instead, the larvae have to find a host for themselves once they hatch. Therefore, they should be able to determine host quality. However, they are unable to detect free-living individuals of their own species, suggesting that they do not have significant interactions with them beyond competition for hosts.[11]

Researchers have explored many mechanisms that protect different hosts from the parasitic behavior of M. ruficauda. Hosts seem to display defense mechanisms both before and after parasitism.[12] In certain cases, the hosts can escape M. ruficauda parasitism some weeks after the original attack. Violent body movements and torsion away from the parasite seem to be some of the most effective behavioral responses that allow for evasion of M. ruficauda.[12] In addition, some studies have suggested that high environmental temperatures increase the probability that the host will successfully kill its parasitoid.[12] M. ruficauda may prefer Cyclocephala in particular because these beetles have a relatively low behavioral reaction to simulated parasitoid attacks; their poor immunological defense strategies make them an easier target for the larvae.[12]

Upon pupating, the larva kills its host grub. The adult fly leaves the pupa and emerges from the soil about 2 months after the eggs first hatched, and begins to prey upon bees and other insects.[13]