202 Illinois State Laboratory of Natural History. 



matal field. This fringe takes so strong a hold on the 

 surface film that the larva cannot release itself by 

 swimming; it does so by looping the head and anterior 

 portion around the posterior extremity, and withdraw- 

 ing the latter through the loop, repeating this action 

 rapidly until it has sunk beyond reach of the film. 



The anterior respiratory tubes ,of the pupa are dilated 

 and membranous at tip, and provided with a terminal 

 pair of membranous flaps which spread out on the sur- 

 face film, thus maintaining communication with the air 

 while the body is concealed in floating trash. Many 

 pupae crawled up on the sides of the breeding-jar when 

 about to transform ; others remained floating. One 

 ])upa cast its larval skin by simply working itself out 

 below through the anterior dorsal split, as the skin hung 

 suspended by the posterior stigmatal fringe. As the lar- 

 val skin is delicate and elastic, the contraction of a few 

 segments sometimes causes a surprising dilatation of 

 one or two adjoining. 



Lama [Fig. 29, 30].— Length 15-18 mm,, diameter 

 1,5 mm.; tapering gently forward from the anterior 

 third, and slightly narrowed at the posterior end. Light 

 yellowish fuscous, or olivaceous, posterior end and ap- 

 pendages more or less thickly mottled with a sooty-black 

 incrustation, extending forward a short distance upon the 

 dorsum ; surface with rather long silky brown pubescence, 

 attached in transverse series, and sparser long erect hair, 

 grouped in five transverse rows on each segment above 

 and below, indistinct except near the posterior end, 

 w^here these hairs are blacker and more conspicuous. 



Head depressed, oblong, middle internal posterior pro- 

 longations broad; black, antennae and mouth parts 

 testaceous, except mandibles, which are black; antennae 

 slender, first joint with an apical seta on each side; 

 second joint cylindrical, very slender, a little shorter 

 than the first; mandibles with two narrow apical teeth, 

 lower edge serrate. Thoracic segments each about equal 



