363 



The apices of the anterior pseiidopods are armed with retractile claws. 

 The posterior pseudopods are elongated, being in Tanypus nionilis 

 Linne very long and widely diverging, their apices armed with two 

 circles of retractile claws which vary in shape and often in color (see 

 PI. XXVI, Figures 5, 9). The anal tufts consist of from six to 

 about twenty long, dark, and rather stout sensory hairs, situated on 

 more or less elongated bases. There are never any blood gills on the 

 eleventh segment, but the twelfth has the usual two pairs on the dor- 

 sal surface, cephalad of which are always two distinct hairs. In many 

 cases the abdomen has numerous surface hairs, though these are so 

 fine as to be almost invisible and are easily overlooked. 



PuPAi, Characters 



Head without any frontal tubercles. Thorax much swollen, respir- 

 atory organs tgg- or trumpet-shaped, never numerously filamented ; 

 wing cases distinctly separated from sides of thorax; no distinct hairs 

 on posterior margin of thorax as in Culicidcc. Abdominal segments 

 slightly flattened, without any sharp transverse ridge at center of each 

 segment as in Di.ra; apical segment ending in two flat appendages, 

 which are either sharp at apex or slightly rounded, and fringed with 

 hairs. In Corethra these appendages are four in number and much 

 more conspicuous. The pupae of Chironomiis and some species of 

 Tanytarsus may be separated from those of Tanypincc by the hairlike 

 filaments of the thoracic respiratory organs. The species of Crico- 

 topus and Orthocladhis are very similar to those of the TanypiiKS in 

 the structure of the thoracic respiratory organs, but the thorax is not 

 so conspicuously swollen, and the apical abdominal appendages gener- 

 ally have a few very long hairs at their tips. 



Imagixal, Characters 



Antennae in both sexes with 2+13 joints; the male generally with 

 long antennal plumosity, the antennal hairs of the female confined to a 

 whorl of much shorter hairs on each joint; frontal tubercles absent. 

 Thorax stout, not protruding over head (PI. XXIII, Fig. 4); pro- 

 notum distinct; sternopleura descending below level of coxae. Ab- 

 domen stout ; hypopygium much simpler than in Chironoimts, the lat- 

 eral appendages ending in a recurved process which is sometimes 

 thornlike, and occasionally slipper-shaped; the dorsal plate (penis 

 guard) very inconspicuous, and the superior and inferior processes 

 indistinguishable (PI. XXVIII, Figs. 1-12). Legs comparatively 

 stout, fore metatarsus always considerably shorter than fore tibia ; 

 fourth tarsal joint occasionally obcordate; claws simple. \Mng vena- 



