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The black fly genus Ectemnia Enderlein possesses a number of autapomorphic (unique derived structural) features in the larval and adult stages that have made resolution of its phylogenetic relationship within the Simuliidae difficult to establish. We studied cocoon-spinning behaviour in Ectemnia invenusta and discovered synapotypies (shared derived behavioural characters) with other black fly taxa. A behavioural phylogenetic analysis performed on representatives of six black fly genera produced a single most parsimonious tree that places Ectemnia as the sister group of a Simulium + sisimulium clade.

The polytene chromosome banding pattern of Simulium exasperans (Craig, 1987) is described for the first time. Three populations of S. exasperans from Moorea and Tahiti were examined cytologically. Interspecific comparisons revealed that S. exasperans is homosequential in chromosomal banding pattern to Simulium cataractarum (Craig, 1987), but contains three species-characteristic floating inversions: IL-1 ex .2 ex , IIL-1 ex ,2 ex , and IIIL-1 ex . No sex-linked inversions were identified; males and females had undifferentiated sex chromosomes. The IIL-1 ex ,2 ex inversion was in Hardy-Weinberg disequilibrium in two of the three populations. From this preliminary data, two cytotypes may exist: cytotype A (Belvedre Cascade population) and cytotype B (1st Afareaitu Cascade and Jardin Public Vaipahi populations). Contrary to phylogenetic and biogeographic data, it is hypothesized that the Belvedre Cascade population (cytotype A) is ancestral to the populations containing cytotype B. Furthermore, a heterozygote advantage may exist in cytotype B.

Polytene chromosomes from the salivary glands of Simulium cataractarum larvae from the islands of Moorea and Tahiti were examined. Intraspecific comparisons revealed a polymorphism in the short arm of chromosome I, termed the IS-1 ca inversion. This inversion sequence was significantly heterozygous in the Tahitian populations (s/i), while the Moorean populations were all homozygous for the standard sequence (s/s). These two island populations seem to be reproductively isolated from one another. Thus, two cytotypes are recognized. Based on biogeographical relationships between the islands, we argue that the Moorean cytotype is likely to be ancestral to the Tahitian cytotype. Furthermore, a heterozygote advantage may exist in the Tahitian cytotype. Chromosomal maps for S. cataractarum are presented.

It is often said that on the Canadian Shield, black flies pollinate the sweet lowbush blueberry, because years with high black fly populations also tend to be those with large blueberry crops. This folklore has never been tested experimentally. Here we report on research designed to test whether or not black flies can act as pollinators for two species of ericaceous plants, sweet lowbush blueberry (Vaccinium angustifolium) and leatherleaf (Chamaedaphne calyculata). In enclosures, black flies may assist in leatherleaf pollination but there is no evidence that they increase fruit set in sweet lowbush blueberry. However, we do not exclude the possibility that in the wild, they act as opportunistic nectar thieves of sweet lowbush blueberry.