Ormia ochracea

Ormia ochracea is native to the southeastern United States, including states such as Texas and Florida. O. ochracea is also found throughout North America, South America, and the Caribbean, though its exact range is not known.

O. ochracea infestation has been shown to affect the behavior and reproduction of host field crickets. Early in the infestation period, non-reproductive behavior is largely unimpaired because the parasitic larvae do not consume the digestive system or central nervous system of the host. After the larvae migrate to the host's abdomen, the host's mating, egg-laying, and fighting ability decline, most likely due to tissue damage caused by the larvae. Additionally, infestation of female crickets alters their mating preferences. Gryllus lineaticeps females normally prefer to respond to male songs with intermediate chirp rates over those with slow chirp rates, but females parasitized by O. ochracea show no preference between chirp rates. Reduced selectivity in infested female G. lineaticeps may be adaptive, as a female may be more likely to reproduce before being killed by the parasitoids if they are less selective.

O. ochracea is a parasitoid known to prey on several species of Gryllus field crickets including Gryllus integer, Gryllus rubens, Gryllus texensis, and Gryllus firmus. Flies have been observed responding to various cricket songs, but seem to be limited to the family Gryllidae. The natural host of the fly may vary by location. Larvae of O. ochracea exhibit highest survival in its natural host and limited survival in other potential host species.

Host-finding. In 1975, William H. Cade experimentally demonstrated that Ormia ochracea uses the mating call of the field cricket as a means to locate its host. Cade placed dead crickets on top of speakers playing cricket songs and various control sounds and recorded the amount of time the fly spent on either the control or test speaker. He found that flies spent more time on the speakers playing cricket songs and observed that the flies would always deposit larvae on and around the speaker which was playing cricket songs.

Learning. O. ochracea have been shown to adjust their preference for host songs after exposure to different songs in the laboratory. In a 2011 study, flies that were previously exposed to the G. lineaticeps song chose the G. lineaticeps song over the G. integer song, and vice versa. This preference was very short term. O. …

Ormia ochracea has the full life cycle of egg, larvae, pupa, and adult. Once a female fly finds a suitable host, she deposits planidia (first instar larvae) which then quickly burrow into the host. The planidia develop within the body of the field cricket host, embedding initially in muscle before migrating into the abdomen. The larvae molt within the host's abdomen and feed primarily on the host's muscle and fat. O. ochracea larvae typically complete development and emerge after about 7 days, which subsequently kills the host. The larvae pupate and emerge as adult flies approximately 2 weeks after emerging from the host.