192 Illinois State Laboratory of Natural History. 



were still being formed April 10 among the few larva& 

 which remained in the cage. 



The imago is said by Osten-Sacken to occur early ia 

 spring, and also, but more seldom, in autumn. Septem- 

 ber 3, I saw a number in flight over a shallow reedy 

 flat, bordering Geneva Lake, Wis. Their singular and 

 ghostly appearance as they floated slowly by with 

 their black and white legs radially extended will never 

 be forgotten. 



Larva [Fig. 15-171. — Full length 50-60 mm., diameter 

 2.6-3 mm., an elongate, rough-skinned larva, with a 

 smooth retractile respiratory tube about 20 mm. long, 

 when extended ; tapering gradually anteriorly to the 

 short broad head; pale rusty brown, surface coarsely 

 granulate, granules blackish when in liquid; covered 

 with regular rows of small setiferous tubercles. 



Head [Fig. 16] fully developed, broad-ovate, convex 

 above, constricted at base; light yellowish brown, lat- 

 eral plates with four more or less curved oblique bands- 

 of confluent black dots at base above, apex of middle 

 triangle filled with black mottlings, in front of this a 

 median double row of dots, and a spot each side; eye& 

 at about middle of side, inconspicuous; antennae in the 

 angle over base of mandible, short, first joint about 

 twice as long as thick, with a terminal seta, second joint 

 very minute; labrum transverse, with two blackish spots; 

 mandibles very short and thick, exterior outline strongly 

 rounded, apex pointed, a prominent tooth within, with 

 an exterior fringe of cilise, and an oblique cutting edge 

 at its apex; maxillary palpi small; mentum bidentate. 



Thoracic segments short, each but little longer than 

 the head, roughly tuberculate; first six abdominals 

 with very inconspicuous sutures and covered with small 

 setiferous tubercles, arranged on the dorsum and venter 

 in regular transverse rows, slightly interrupted on 

 the median line, limited each side above and below bj 

 a longitudinal smooth line; on each side between these- 



