Concerning Rheumatobates rileyi Bergroth (Gerridae)

TitleConcerning Rheumatobates rileyi Bergroth (Gerridae)
Publication TypeJournal Article
Year of Publication1953
AuthorsHungerford HB
JournalEntomological News

To me, Rheumatobates is the most interesting genus in the Gerridae. The bizarre modifications of the antennae and legs of the males in many species are strange indeed! These little striders are exceedingly lively and nervous creatures and difficult to keep in captivity. In 1920 I reported that the females are provided with an ovipositor for inserting the eggs in plant tissue and figured both the ovipositor and the fully developed ovum. I did not discover the deposited eggs either in field or laboratory. In 1923 at the University of Michigan Biological Station, I found large numbers of Rheumatobates rileyi palosi Blatchley on the slowly moving water of Bessey Creek but did not succeed in transporting many live specimens across Douglas Lake to the station laboratory. In 1927, J. K. Gwynn Silvey, at my suggestion, undertook a study of the life history of this species at the Biological Station and continued his studies during the summer of 1928. He published his results in 1931. He described the mating behavior, reported a female ovipositing in the tissues at the base of a Potamogeton leaf and figured the eggs, five nymphal instars and adults. His plate is quite satisfactory but the legend incorrect, Figure 3 being the fifth instar not the first; figure 7 the first not the fifth, etc. No precise dates are given in this paper and nothing to indicate that any specimens were reared from egg to adult. More work should be done on the biology of Rheumatobates. It may be helpful to know that the best way to bring these insects from field to laboratory is to place toweling paper in the bottom of a minnow bucket, moisten the paper and let the Rheumatobates drop from the dip net into the pail. Do not permit too much water to drip from the net into the pail and the insects will survive a considerable journey on the moist paper. In the laboratory, instead of using aquaria containing water I have had better success with finger bowls and large seven inch stender dishes in the bottoms of which had been placed several layers of toweling paper moistened but not too wet. The female Rheumatobates insert their eggs into and often protruding through the top layer of paper. While it is extremely difficult to locate the oviposition punctures from above, by peeling off the top layer of paper and examining its under side the eggs are readily found, either plainly protruding and exposed or but thinly covered by paper fibers, as shown in the text-figure. Pieces of paper containing eggs may be cut out and placed in small stenders for following the embryological development and hatching of these insects. This same technique has been used with success in rearing Mesovelia which also lays its eggs in the paper and with Microvelia, Hydrometra and other surface forms that simply attach their eggs to the paper. It is suggested, therefore, that losses from drowning that occur in aquaria may be avoided in studies of other semiaquatic Hemiptera and may facilitate the rearing of these insects.