TRANSFORMATIONS OF BUFFALO GNATS. 9 



At Dallas, Tex., in March, 1913, S. vittatum was found by the 

 writer ovipositing in considerable numbers on the small stones in 

 the limestone bed of a small stream which was almost devoid of 

 submerged herbage. The eggs were laid generally below or at the 

 surface of the water. In a few instances they were found an inch 

 or so above the water, but this was owing to a decrease in the amount 

 of water, which varies considerably in this and the majority of 

 streams in Texas. This species has been found by the writer on one 

 occasion at Havana, 111., ovipositing in large numbers on the bridge 

 piles in the Illinois River. The eggs were deposited at or just below 

 the level of the water, and as the river was falling at the time at the 

 rate of an inch a day, the eggs underwent complete desiccation, and 

 all were destroyed. The bridge piles were literally covered with the 

 matrix and eggs, and many females, becoming entangled, died adher- 

 ing to the viscous masses. This oviposition of this species in the 

 main river seems to have been an abnormal occurrence, as the larvae 

 have never been found in this situation. Another species, however, 

 S. johannseni, according to the writer's observations, breeds in 

 enormous numbers in the main channel in the spring, around the 

 submerged vegetation near the banks and wherever there is an 

 obstruction. 



S. venustum, in the regions studied, belongs entirely to group 2. 

 The eggs are laid on submerged grass blades and the like in small 

 streams, in situations similar to those selected by 8. vittatum. The 

 eggs are more evenly arranged than those of that species, the matrix 

 is not smeared so profusely, and the egg mass is generally oblong 

 in shape and very compact. This species has many times been ob- 

 served ovipositing, and specimens which subsequently laid a full 

 quota of eggs in captivity were taken from the stream as they 

 alighted. 



The oviposition in captivity of S. venustum was observed by the 

 writer at Spartanburg, S. C, on September 16, 1913. A female 

 S. venustum was noticed at 5.08 p. m. moving up and down a small 

 stream within a space of about 4 feet, apparently seeking a suit- 

 able place for oviposition. She would touch the water for an in- 

 stant and then, apparently dissatisfied, fly up again. This peculiar 

 interrupted flight was continued for a period of two minutes, after 

 which she alighted on a grass blade which seemed to be satisfactory. 

 Immediately a bottle was placed over her and she was at once taken 

 to the laboratory. The stream from which the specimen was taken 

 was situated 50 yards from the laboratory, and thus little time was 

 lost in transit. The bottle in which the specimen was taken was 

 partly wet inside. At 5.13 p. m., as soon as the bottle was placed on 

 its side, she felt around for two minutes and then settled into posi- 

 tion, rapidly thrust out the end of her abdomen, and deposited an 

 10981°— Bull. 329—16 2 



