MAY FLIES AND MIDGES OF NEW YORK 83 



terrestrial larvae of Oeratopogon have prominent spines 

 and setae upon the body, while the aquatic forms are nearly 

 devoid of them (pi. 17, figs.l and 4) . The aquatic larvae of Oera- 

 topogon have no prolegs and the body is very slender and 

 snake-like. The larvae can exist at great depths, and have been 

 lished up from the bottom of deep lakes. They have been found in 

 salt water (Packard, -TOa). 



The pupae 



The pupae of Ohironomus are frequently found in the old 

 larval cases ; others swim very freely near or at the surface after 

 the fashion of a pollywog. The pupa of Tanypus is active 

 and resembles that of C u 1 e x in form and habit. The pupa of 

 the aquatic Oeratopogon is more elongate than Tany- 

 pus, is not active, and floats, nearly motionless, in a vertical 

 position. All of the pupae have an enlarged thorax and usually a 

 pair of respiratory tubes or filaments, while the caudal end is 

 somewhat broadened and paddle-like or prolonged into two- 

 pointed lobes, Avith ciliate margin. 



The imagines 



To the imaginal characters of the family already given the fol- 

 lowing may be appended : 



The head is small, spheroidal, flattened where it joins the 

 thorax, in some genera somewhat hollowed out between the eyes. 

 The compound eyes are large, with conspicuous facets and dis- 

 tinctly separated from each other. They are kidney-shaped (reni- 

 form) ; that is, hollowed out around the base of the antennae. 

 The ocelli are wanting. The front, the space between the eyes, is 

 limited by the upper margin of the head and a line drawn through 

 the root of the antennae. The vertex is the uppermost part of the 

 front, near the margin of the occiput. 



The face is the portion below the antennae, which is prolonged 

 more or less downward to form the proboscis. The oral margin 

 and an indefinite space immediately contiguous to it is called the 

 epistoma or peristoma. The epistoma is usually convex, provided 

 with setae or sensory hairs. The maxillary palpi are the slender, 

 usually four-jointed appendages, the most conspicuous of the 

 mouth parts. The labrum, hypopharynx and labium differ with 



