The phantom midges (Diptera: Chaoboridae) are a relatively small fly family composed of 50 extant species in six genera. Larvae are of interest to limnologists and ecologists because of their tolerance to toxicants, predatory avoidance strategies, and the role chaoborids play in zooplankton community dynamics. Relative to mosquitoes, systematists have paid relatively little attention to this group. Recent work on the internal classification of the chaoborids has provided a wealth of character information and putative homologies, but the relationships among the Chaoboridae genera have not been rigorously analyzed and support for the monophyly of the family is weak. The objectives of this research are three fold: 1) test the monophyly of Chaoboridae; 2) examine subfamilial and species relationships within the family; 3) develop and explore new character systems useful across the Culicoidea.

The fatigue crack growth rate (FCGR) of a nitrogen-strengthened high-manganese stainless steel of nominal composition 18Mn-5Ni-16Cr-0.02C-0.22N was determined in the intermediate stress-intensity factor range (20-70 MPa?m) at 77 and 4 K. Fractographic investigations were performed on the fracture surfaces. The FCGR at 4 K was very nearly the same as at 77 K and substantially below the FCGR for AISI 304LN steel. The fracture surfaces of both the high-manganese alloy and the 304LN showed a transgranular failure mode, but the detailed fractographic features varied with temperature and alloy type. The fractography was closely related to changes in the FCGR.