280 



ized tube-like process, which is armed with a number of long hairs, 

 and ending below in a pair of slightly pointed processes which are 

 fringed with closely placed hairs. 



Pupa (PI. XL, Fig. 7). — Antennae extending to or beyond middle 

 of wings; palpi forming a semicircle, their apices incurved in front 

 of clypeus; eyes rather small. Thoracic respiratory organs elevated, 

 funnel-shaped ; legs recurved against base of abdomen. Abdomen 

 with 3 rather distinct sharp ridges on each segment, the apices of 

 which are slightly serrate; apical segment terminating in 2 long, 

 pointed processes; apical half of abdomen directed cephalad because 

 of the curvature of the body, thus closely resembling the pupae of 

 Culicidae. 



Imago. — See key to imagines of Nematocera. 



HABITS OF LARVAE 



The larvae are aquatic, living in shallow wells, and in clear water 

 such as is found in springs and slow-flowing mountain streams. The 

 food consists of algae. 



HABITS OF IMAGINES 



The imagines occur in the vicinity of streams and may be swept 

 from grasses or other vegetation overhanging the water. I have 

 found them very commonly among grasses on almost perpendicular 

 rocks that were continuously wet owing to water dripping over their 

 surface. They have poorly developed mouth-parts, but I have found 

 them on flowers, evidently feeding on nectar. 



I have before me examples of the larvae and pupae, some of which 

 were obtained by Mr. Hart at Havana, 111., and others by Dr. S. A. 

 Forbes in Yellowstone National Park. They differ from the species 

 described by Johannsen in the armature of the abdomen and the struc- 

 ture of the apical segment, and in a few other particulars. 



Paper containing Account of North American Dixidae 



Johannsen, 0. A. 



'03. Aquatic Nematocerous Diptera. Bull. 68. Pt. 6, N. Y. State 

 Mm, pp. 429-432. 



Superf amily Cliironomoidea 



This superfamily contains 3 families, Chironomidae, Ceratopogon- 

 idae, and Orphnephilidae. 



