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Tiger beetle; life cycle; larval development; dormancy; seasonality; Amazon; inundation; Megacephala
Abstract:
The life cycles of 4 of 11 tiger beetle species known to occur in open areas of Central Amazonian floodplains were studied during 1997-1999 in the Manaus region. Regular field excursions were undertaken over a period of 2 years to follow larval and adult phenology (one site in a whitewater area [várzea], another in a blackwater area [igapó]). Beetles collected in the field were taken to the laboratory for examination of gonad maturity. Additional larvae were reared under controlled conditions in the laboratory from egg to adult beetle. All species had annual life cycles. Larval development was studied in the field and laboratory for 3 species (Phaeoxantha klugi, P. lindemannae and P. aequinoctialis). Duration of all developmental stages are given. Larval development in the laboratory was generally faster than in the field, ranging from 3,5 to >7 months depending on the species. In the field, larval development lasted between 7-10 and 10-14 months. A period of dormancy varying in duration was observed in 3rd-instar larvae before pupation. Because hatching of the new beetle generation was more synchronized than the distribution of the 3 larval instars, we presume that dormancy is used to adjust the populations to the seasonally changing environmental conditions imposed by a monomodal flood pulse. In P. klugi and P. lindemannae, larvae survived the inundation period submerged in the soil. The beetles that hatched thereafter had a short life span of only few months. Although the larval phenology is similar in P. aequinoctialis, adult life span was with >6 months extremely long. Data on the life cycle of the fourth species (P. limata) are scarce as larval phenology is still unknown. The type of life cycle with a long larval phase contrasts with other findings for floodplain species from the Manaus region, and is considered similar to patterns found in species from terra firme uplands as well as in subtropical and temperate regions
