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Abstract:
Tiger beetles of the genera Phaeoxantha Chaudoir and Tetracha Hope are considered to be flightless or to fly only occasionally. Six species of these genera inhabit Central Amazonian floodplains and show strong differences in life cycles, behaviour, and habitats. From this background we investigated flight ability in these species by determining flight muscle development in specimens regularly collected between 1997-1999. Gonad states (in females) as well as teneral females were recorded to estimate beetle age. Of 1,946 adult beetles of these six species we dissected, 31.4% had fully developed flight muscles, suggesting flight ability. In the other 68.6% of specimens flight muscles were completely absent. Frequency of flight muscle presence varied greatly among species, ranging from 100% in Tetracha species, and 0 to 60% in Phaeoxantha species. No evidence for an "oogenesis flight syndrome" was found in females as flight muscle states were not correlated with age. These findings are interpreted as flight (muscle) dimorphism in Phaeoxantha species. Flight muscle presence in males and females was only different in P. klugii Chaudoir with flight ability being more frequent in females. Tetracha species use flight as an integral part of their survival strategy in Central Amazonian floodplains, unlike Phaeoxantha species. A possible correlation between the degree of flightlessness and habitat stability in Phaeoxantha species is discussed.
