1 904] GIRA ULT:— TA NY PUS D YARI 8 1 



TANYPUS DYARI COQUILLET: PUPA AND ADULT EXCLUSION. 



BY A. ARSENE GIRAULT, PARIS, TEXAS. 



While walking along the edge of a small mountain pond near the town of 

 Blacksburg, Virginia, March 14, 1903, my attention was attracted to numerous pupal 

 casts scattered over the surface of the water, especially numerous along the margin 

 of the pond, clinging to pieces of old logs and fence-rails extending out into the 

 water. 



Simultaneously with this, grayish, slenderly built flies were occasionally seen 

 rising from the water, and were at once connected with the floating exuviae. A 

 few moments later they were observed emerging from their pupal skins. 



Pupae. — The pupae locomote by quick, jerky, motions of the abdomen, the 

 caudal end of which is forked ; violent outward movements send them forward in 

 a kind of a jerky revolving motion not unlike an acrobat turning many somer- 

 saults from some high position, though, of course, the pupae do not actually revolve,, 

 but apparently so. 



They resemble mosquito pupae ; light brown, shaded along the stigmatal line 

 with olivaceus ; eyes prominent, oval, deep brown ; two brownish siphuncles are 

 borne on the dorso-lateral aspect of thorax, one on each side ; the latter protrude 

 from the water when the insect takes its position at the surface of the water, which 

 is often the case. 



Normally, the pupae remain at the bottom of the pond, near the edge, under 

 sticks and leaves, and when the latter are disturbed, shooting out in all directions. 

 They are often seen at the surface, beside logs, where they rest with the abdomen 

 curved under against the head and thorax. 



Emergence takes place from a longitudinal rent in the thorax, and the fly 

 uses the pupal skin to a certain extent as a float or support while its body and 

 wings are drying. This, of course, is excepted, if it can find other support, which 

 is often the case, as when the pupa has drifted against a log or a leaf, the excluded 

 fly then abandoning the pupal skin for the more substantial support afforded by 

 whatever object it may have drifted against. If in open water, and the wind is 

 blowing, the fly perchance takes a short cruise, before it finally rises. 



Exclusions — Pupa observed in about \ inch of water ; very restless, and much 

 paler than normal ; lay quiet for awhile, extended full length and gave violent 

 jerks with abdomen as if straining to break pupal skin. Very restless, then list- 

 less ; floated about on surface of water, and finally came to rest against a bunch 

 of grass growing in the water. 



