Degree Name

Master of Science (MS)

Semester of Degree Completion

1985

Thesis Director

Kipp C. Kruse

Abstract

Various factors affecting the availability of male back space in the giant water bug, Belostoma flumineum Say, are described herein and interpreted in a manner consistent with natural selection theory. Newly emerged males are observed to breed and accept eggs sooner than newly emerged females develop an egg clutch: furthermore, newly emerged males were shown to contain motile sperm on the day of adult emergence. Newly emerged females did not contain any mature eggs until approximately six days old. It was also found that newly emerged females manufacture eggs at a linear rate of 4.8 eggs per day. Egg length was found to increase significantly with age: egg width did not. Asynchronous breeding (one female ovipositing on more than one male) appears likely to occur. This would skew the operational sex ratio towards females since fully encumbered males or males which have brooded eggs for several days (and are not receptive to further oviposition) are no longer available for mating. Females appear to oviposit a partial clutch on an available male rather than delaying breeding and yolking up a larger clutch that may completely encumber one male. To obtain a full pad, partially encumbered males may solicit eggs from more than one female for up to five days after original oviposition. Since egg brooding constitutes a shareable parental investment, females should not prefer unencumbered males over partially encumberd males. If asynchronous breeding favors a female biased operational sex ratio (OSR) and sexual maturation time favors a male biased OSR, then it seems logical that the OSR will vary significantly throughout the breeding season. My results suggest that male back space may be limiting for female reproduction during the early part of the summer, in which the first nymphs have not yet matured, but probably is not limiting after young-of-the-year start emerging into the population.

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