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 irregular 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 View. 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 
