Use of Horns in Fights by the Dimorphic Males of Ageopsis nigricollis (Coleoptera, Scarabeidae, Dynastinae)
نویسنده
چکیده
Brief observations of the behavior of males of the dynastine beetle Ageopsis nigricollis suggest that the males use their horns as weapons in intraspecific fights. Mea surements of nearly 200 males show that there are two different morphs. Thoracic but not head horns are missing in the minor morph, and behavioral observations confirm that thoracic horns are less useful for smaller individuals. The functions of the horns of most horned beetles are still unknown, although observations of their use in intraspecific combat are slowly accumulating (Eber hard, 1979, 1981, 1983; Moron, 1978; Brown, 1980; Thomas, 1981; Goldsmith, 1985; D. Windsor, pers. comm.). This note presents fragmentary observations of the dynastine Ageopsis nigricollis Sternberg. It appears that this species, which has both cephalic and thoracic horns in the male (Fig. 1) but not the female (Enr?di, 1985), also uses its horns as weapons in intraspecific battles. The study was performed on the eastern plains (llanos) of Colombia at the agricultural research station "Carimagua" on the western edge of Lago Carimagua, and at an adjoining ranch. The beetles were found in 1978 only during a very short period just after the rainy season began. On two consecutive evenings (3 and 4 April) they appeared at lights in large numbers. On the three succeeding nights they became more scarce and subsequently disappeared. All individuals found were males. Lengths of head and prothoracic horns and maximum pro thoracic widths were measured with vernier calipers (Fig. 1).
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