226 THE UNIVERSITY SCIENCE BULLETIN. 



Shape. A little more elongate than in first instar, the width now 

 about half the body width. 



Color. Eyes very dark red, as are the dorsal abdominal glands. 

 Cephalic aspect of head shows the cephalic end of the median dark longi- 

 tudinal band, noted below. This band extends down upon the front to 

 the level of the lower inner angles of the eyes. A dark spot lies lat- 

 erad of the lower end of the median band, about three-fifths to two- 

 thirds the distance to the inner angle of the eye. Dorsal aspect: head 

 with median longitudinal smoky band visible from front to highest point 

 of vertex. Between the caudal end of this line and the eyes lie two 

 pairs of dark, more or less elongate, spots. The prothorax is marked 

 on each side with two dark, roughly triangular spots of unequal size, 

 their apices directed toward the margins. The smaller spots just laterad 

 of median line and the larger ones laterad of these. The prothorax 

 often marked by a transverse band on caudal margin. The mesothorax 

 is marked by three pairs of very irreg-ular and often indefinite, smoky 

 blotches of unequal size. The abdomen is marked by reddish transverse 

 bands that follow the abdominal sutures. These give way to triangular 

 sooty blotches at the margins. The two large, dark dorsal glands have 

 arcuate anterior margins and convex posterior margins. A dark circular 

 spot marks the anal opening. The middle limbs have the joint between 

 femur and tibia slightly smoky, and the tarsus is crossed by faint median 

 band. The tibio-tarsal joint of hind leg is dark and a band crosses the 

 middle of the tarsus. A dark spot on the hind tarsus is characteristic of 

 all the nymphs of this species, and mark them from the nymphs of 

 Arctocorn.va alternata taken at the same time. 



Structural Peculiarities. The hairs on limbs in more definite series. 

 Swimming fringe of hind legs still confined to margins of tarsus for 

 the most part, but composed of a larger series of more closely set hairs, 

 some 40 in number. The claws of the hind tarsus are now one-third the 

 length of this segment, and appear incised about midway of their length. 

 The relative lengths of limb segments much as in the previous instar, 

 but the entire limb more slender. The marginal series of spines as 

 delineated in the figure. The pair of peg-like spines astride the median 

 line on caudal margin in this and all other instars. A cluster of five 

 long spines at caudo-lateral angle of last segment and about five short 

 ones anteriorly. The penult segment of abdomen is margined by five 

 spines, the second one from the caudal margin elongate. The ante- 

 penult segment of abdomen is margined by about seven spines, the first, 

 second and fourth longer than the others, the second one being twice 

 as long as any of the rest 



Third Instar. 



Size. Length, 2.21 mm.; width of body, 1.04 mm.; width of head, 

 0.806 mm.; distance between eyes, 0.286 mm. 



Shape. Length now two and a fifth times the width. 



Color The face has the dark blotches between the lower inner angle 

 of eye and the dark longitudinal median line of former instars. In 

 dorsal view the head is marked either side of the longitudinal median 



