Dytiscidae and Noteridae of Wisconsin (Coleoptera). IV. Distribution, Habitat, Life Cycle, and Identification of Species of Agabini (Colymbetinae)

Adults of 24 species of Agabus and 10 species of Ilybius were collected in Wisconsin over the last 32 years. Keys and notes on identification are pro­vided to facilitate identification of adults of these species and six others that may occur in Wisconsin. Agabus larvae were separated from those ofIlybius by the more posterior position of the dorsal seta of the basal setal whorl on the urogomphus, the number and location of srines on the metatarsi, and the presence of long setae on the last abdomina segment of most species. Information on distribution and abundance in Wisconsin, habitat. and life cycle is provided for each species based on collection records for 8,460 adults, and those larvae that could be identified with reasonable certainty. All species of Ilybius had similar life cycles. which were predominantly univoltine with larvae overwintering and completing development in the spring. and partially semivoltine with both adults and larvae overwintering. Lentic species of Agabus had three types of life cycles, with most larvae developing in spring. Types 1 and 2 were univoltine with adults overwintering in aquatic habitats (type 1) or terrestrial habitats (type 2). Type 3 life cycles were mostly univoltine with eggs overwintering, but also semivoltine to varying degrees with adults also overwintering in terrestrial habitats. Lotic species of Agabus had variable univoltine life cycles with adults, and sometimes also larvae, overwintering