188 THE UNIVERSITY SCIENCE BULLETIN. 



tex plainly less than the width of one of the eyes. The femora of the 

 middle legs now have two strong spines on the posterior margin. The 

 basal one is borne upon a strong tubercle. 



Third Instar. 



Size. Length, 3.51 mm.; width of body, 2.21 mm.; width of head, 

 1.56 mm. 



Color. For color pattern see later instars. 



Structural peculiarities. Ventral view: The limbs are all equipped 

 with spines. Some of these on the front and middle legs are arranged to 

 effect a loose guard of hairs when the limbs are flexed. The front and 

 middle limbs are also flat or concave on their posterior side and guarded 

 on either margin by several spines. The front tibia has an iri'egular row 

 of about six in the ventral edge of its posterior margin, and a definite 

 row of the same number on the dorsal edge of this posterior margin. 

 The tarsus is shorter than the tibia and has two spines on either margin 

 and ends in two well-developed, subequal claws. The middle femur is 

 thickened and on its posterior border are three long spines, the basal 

 one on a strong tubercle and a short peg-like one. The middle tibia has 

 3 spines on its anterior margin, six short ones on the ventral margin 

 of the posterior side, and three long ones on dorsal margin of this same 

 side. The dorsal caudal margin of tarsus is provided with four spines 

 and the tarsus is terminated by two unequal claws, the upper one of 

 which is nearly a half larger than the lower. The hind limbs are 

 strong and furnished with many short spines. The posterior margin of 

 hind femur has a row of these short spines, eight or nine large ones 

 quite evenly distanced one from another, and three spines are present 

 at distal end of the ventral side of femur. Several rows of short spines 

 on tibia and tarsus and swimming fringe on both of these segments. 



Dorsal Vieiv. Posterior margin of mesothorax more deeply arcuate, 

 the wing-pads extending back more than one-third of the length of the 

 margin of the mesothorax and metathorax together. Margins of abdomen 

 barred with dark markings, base of second abdominal segment very 

 dark also. 



Fourth Instar. 



Size. Length, 7 mm.; width of body, 3.12 mm.; width of head, 2.08 

 mm.; distance between eyes at vertex, .91 mm.; distance between eyes 

 at closest point, .52 mm. 



Color. As in fifth instar, save the dark band on mesothorax. Wing- 

 pad is single and broad. 



Structural Peculiarities. Ventral view: General arrangement of 

 spines on the legs about as in third instar ; front tibia as in third instar ; 

 front tarsus shows the two spines on the dorsal edge of the posterior 

 margin, the other spines obscure. Middle femur now shows a definite 

 tuft of about four strong spines arising from the tubercle, two other 

 strong spines (sometimes a weaker one also) and a black-tipped spur or 

 tooth not far from distal end of femur. The middle tibia has six spines 

 either side of the posterior surface and three or four on the rounded 



