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Some observations on the making behavior of the giant walking stick, Megaphasma dentricus (Orthoptera: phasmidae).

Article Excerpt
Sexual dimorphism is a prominent feature throughout the animal kingdom, from birds to ungulates to arthropods (Blanckenhorn et al. 2007). In many stick insects, sexual dimorphism is two-fold. First, the males may bare enlarged femoral spines, perhaps used as weapons in male-male competitions (Sivinski 1978; Brock 1999). Second, the males can be smaller than females, which may be a benefit to both males and females, as during mating, the male hangs on to the female, and a smaller male may allow the female to be more mobile for feeding and/or have more energy to invest in reproduction (Sivinski 1978). However, the idea that relatively small males have a higher fitness than large males is contradictory to a body of sexual selection theory that suggests that larger males, specifically in species that have weapons and engage in male-male competitions, often obtain more matings (Andersson 1994). The preliminary observations on the male-male and male-female interactions in the giant walking stick Megaphasma denticrus (Stal; also referred to as Megaphasma denticrum), while too few for statistical analyses, suggest that future investigations of the following hypotheses could be profitably pursued: (1) males compete with each other over access to females or resources, (2) large males are more likely to mate than small males, (3) males missing legs (autotomy) experience any mating disadvantages, (4) males prefer large females, and (5) females prefer small males.

The giant walking stick is one of the largest phasmid species in North America and is found in the south central United States (Figure 1; Hebard 1943; Wilkings & Breland 1951). Both sexes have femoral spines on their mid and hind legs, but males have a single large spine and...

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