THE BIONOMICS AND MORPHOLOGY OF NEW ENGLAND SPONGILLA-FLIES (NEUROPTERA: SISYRIDAE)

Larvae of the small insect family Sisyridae (Neuroptera) are parasites of fresh-water sponges (Porifera: Spongillidae). Little detail was known of their ecology and comparative morphological studies and revisions were few. This work is a comparative study of the ecology and internal anatomy of two sympatric New World species found in Connecticut: Sisyra vicaria Walker and Climacia areolaris (Hagen). The data aid in understanding the evolutionary history and phylogenetic relationships of the Sisyridae and the Neuroptera.^ Laboratory colonies and monitoring of field populations revealed that C. areolaris is bivoltine and overwinter as aquatic second instars. Larvae of each generation utilize photoperiod to initiate and terminate diapause. Sisyra vicaria is univoltine and overwinter in terrestrial eggs as pharate first instars. Photoperiod has little apparent control over diapause expression. Sisyra vicaria appears after the first generation of C. areolaris. It is concluded that ecological interactions between the species are slight or non-existent. Larvae of both species are non-host-specific, utilizing seven species of Porifera. Adults are nocturnal scavengers. Fecundity, embryonic development, hatching, and predators and parasites were also studied.^ The internal anatomy of sisyrids and other neuropterans was studied through comparative dissections of specimens and examples from the literature. There are few major differences between the egg chorion, egg burster, or digestive, neural, and reproductive systems of C. areolaris and S. vicaria. However, the neural and female reproductive systems differ greatly from that of other neuropterans. At metamorphosis, four ganglia of the sisyrid ventral nervous system fuse with other ganglia; in other neuropterans, only two become fused. Study of the internal female reproductive system shows that a major duct, the fertilization canal, is missing in the Sisyridae but present in nearly all other Neuroptera and Megaloptera. Presence of the duct in Raphidioptera indicates the canal is a symplesiomorphic character for these three sister groups. Sisyrids have apparently lost this canal.^ It is concluded that, sisyrids have broad ecological tolerances and facile life history strategies; though phylogenetic relationships remain obscure, sisyrid morphology indicates a long and independent evolution separate from other neuropterans.