(A) The black crab (Gecarcinus ruricola, black morph). (B) The male holotype of D. endobranchia collected by H.L. Carson in 1966, now in the collections of the National Museum of Natural History, Washington, D.C. (C) Grand Cayman; Numbers refer to sites were crab flies were found. Scale bar 5 km. Image courtesy of NASA. (D) Male fly courting a female fly under the watchful eye of their host (a yellow morph black crab). (E) First instar fly larvae are found in the nephric pads (yellow arrow). The larvae feed on microorganisms, which cleanse the urine (exuded from the green gland; red arrow) of nitrogenous waste compounds. (F) Second instar is spent inside the gill chambers.