The fourth stage larva of Deinocerites cancer can be distinguished from those of other Florida mosquitoes by its circular shaped head which is widest near the bases of the antennae, an anal segment with dorsal and ventral sclerotized plates, and a single pair of short bulbous anal gills.
Waste products from land crabs probably enhance mosquito production by providing a food source for the larvae. By removing excessive debris and soil from their burrows land crabs also help to maintain an aquatic habitat for the crabhole mosquito. Without a resident land crab, old burrows rapidly become unsuitable for crabhole mosquitoes. Cardisoma guanhumi are herbivorous and normally remain in the burrows during the daylight hours, venturing out to feed only after sunset. This daily pattern of activity is interrupted when land crabs occasionally seal the entrance to their burrows with an earthen plug which may remain in place for several weeks or months. Crabhole mosquitoes may be trapped in these capped burrows.
Another inhabitant of land crab burrows is the killifish Rivulus marmoratus, which is particularly common in burrows that are more likely to be inundated by storm or seasonally high tides. Rivulus marmoratus can survive in the low oxygen and high hydrogen sulfide concentrations characteristic of the small, isolated aquatic habitats in land crab burrows, and it will readily devour Deinocerites cancer larvae. Other unusual traits enhancing the capacity of Rivulus marmoratus to prey on crabhole mosquito larvae include: the ability to move from one crabhole to another one by scooting over damp soil; the capacity to lay eggs with delayed hatching under drought conditions; and the self-fertilizing hermaphroditic mode of reproduction which enables a single fish to colonize new habitats.
During the late summer and fall, estuarine water levels along Florida's southeast coast typically are much higher than they are during the rest of the year. These high water conditions invariably flood and submerge many land crab borrows near the estuarine intertidal zone, making the Deinocerites cancer larvae easy prey not only for Rivulus marmoratus but also for several other fish species. Nevertheless, land crabs adjust to these major floods by relocating further inland, and their new burrows are rapidly colonized by Deinocerites cancer.
The transformation from an aquatic to a terrestrial creature takes place in the non-feeding pupal stage. Deinocerites cancer pupae, like those of all mosquito species, are motile but tend to be inactive unless disturbed by other organisms. The pupal stage lasts just a few days.
Newly emerged Deinocerites cancer females are sexually receptive to males, whereas the females of several other mosquito species will not mate for one or more days following emergence. Male Deinocerites cancer spend a considerable amount of time on the surface of the water where they exhibit a behavior called pupal attendance. The exceptionally long antennae of male Deinocerites have fewer sound collecting fimbrillae but more olfactory and mechanoreceptive sensilla than the males of other mosquito species. Using their highly specialized antennae, they search for female pupae. Once a pupa is located, the male attaches to the pupa's air trumpet with the tarsal claw of its foreleg, while the other legs will be used to fend off other males. Somehow male Deinocerites cancer can distinguish between male and female pupa, especially in the final hour before eclosion. An attending male will initiate the mating process even before an emerging female is free of her pupal case. Copulating pairs may remain together for 30 minutes or more. Pupal attendance is known to occur in only one other mosquito, Opifex fuscus.
Deinocerites cancer females normally do not blood feed until after the first egg clutch, which is produced with carry-over reserves from the larval stage, is deposited. Birds, particularly ciconiiforms, serve as the primary blood source, but feeding also occurs on various mammalian and reptilian species. No evidence has been obtained to support the assertion that land crabs serve as a blood source for Deinocerites cancer. Both males and females obtain sugar meals from floral and other plant sources.
Author: George F. O'Meara, Florida Medical Entomology Laboratory, University of Florida
Photographs and Graphics: David Mook, St. Lucie Mosquito Control Unit, Florida; Michele Cutwa and James Newman, University of Florida; and Joe O'Neal
Project Coordinator: Thomas R. Fasulo, University of Florida
Publication Number: EENY-134
Publication Date: May 2000. Latest revision: 2004.
Copyright 2000-2004 University of Florida
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Department of Entomology and Nematology
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distribution
burrows
great Atlantic land crab
male and female
4th stage larvae
sealed land crab hole
killifish
pupa
pupal attendance
male attached to pupa