Aquatic Insects of Michigan

by Ethan Bright, Museum of Zoology Insect Division and School of Natural Resources and Environment
University of Michigan

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Gelastocoridae - The Toad Bugs

Only one species of this small family is found in Michigan, Gelastocoris oculatus (Fabricius). Normally a semi-aquatic (riparian) species, specimens are sometimes found some distance away from water, or by the water's edge in semi-inundated water. Most specimens are found among sand or mud along both lotic and lentic habitats.

Description (from Todd 1955)

    Size. Male: Length, 6.1 to 8.0 mm.; width of pronotum, 4.0 to 5.3 mm.; width of abdomen, 3.9 to 5.2 mm. Female: Length, 6.7 to 9.3 mm.; width of pronotum, 4.3 to 5.9 mm.; width of abdomen, 4.4 to 6.0 mm. Color. Extremely variable both as to color and pattern. Colors present are black, brown, red, orange, yellow, white and green. Legs are ringed with brown. It would be an endless and useless task to try to describe all of the combinations of colors and patterns. In general, the specimens from the southeastern United States are smaller and darker, while those from the rest of the United States tend to be larger and lighter, but both extremely dark and extremely light forms as well as all intermediates may be found in either area.

Structural characteristics

    Head. Apex of head rounded or weakly pointed; front moderately rough, provided with low, broad elevations which vary in size with the specimen; ocelli rather small, equal to or slightly larger than the blisterlike granules of the hemelytra.

    Pronotum. Pronotum with the disc moderately rough, though the degree of roughness varies with the specimen; lateral margin quite variable, usually with anterior portion subparallel for a distance equal to two-thirds the length of the ocellocular space, slightly divergent, then lateral margin extending diagonally posterolaterad to the lateral angle, in some specimens this portion of the lateral margin may be nearly transversal, usually this portion of the lateral margin is convex, more rounded toward the lateral angle, lateral margin weakly serrate; posterolateral margin extending diagonally posteromecad to base of embolium, serrate; lateral angle projecting laterad beyond the base of embolium; width of protonum subequal to width of abdomen; base of pronotum lacking short, longitudinal carinae.

    Hemelytra. Hemelytra extending beyond the end of abdomen; membrane well-developed; basal half of lateral margin of embolium expanded, width of expansion about three times as wide as largest blisterlike granule, expansion forming an obtuse angle posteriorly. Connexivum prominent. The blisterlike granules few in number, slightly less in width than base of hind tarsus.

    Abdomen. Spatulate right side of seventh ventral abdominal segment of male about half covered by the preceding segment, not extending to the lateral margin of the abdomen; left side projecting posteriorly only slightly. Female ventral abdominal segments nearly symmetrical, the incision may be symmetrical or bent to the left. Keel hood of male genitalia broadly triangular, apex blunt, an oval concavity near apex on the ventral surface, fringe nearly transversal, somewhat concave in center; keel hook present, rather stout, recurved and apex extending partially over pan; pan with apex thick, but narrow, about one-half width of base, with a slight depression on ventral surface, base more flattened, pan as whole in plane at right angle to the dorsoventral axis of the insect; right clasper hook quite variable, usualIy apical half digitiform, usually rather thin, transversal portion of base variable as to thickness, there may he a lateraI projection present at the base of digitifom process, this also is variable in size; tumescence of right clasper not adnate to basal portion of clasper; anterolateral projection of keel absent.


    Todd EL. 1955. A taxonomic revision of teh family Gelastorcoridae (Hemiptera). The University of Kansas Science Bulletin 37(11):277-475.