hungerford: aquatic hemiptera. 225 



The attachment disc of the egg is smaller than in some of the other 

 species. Two eggs are figured on pi. XXVIII, fig. 15. These are drawn to 

 same scale and show the difference in size and shape between the newly 

 laid egg and the older egg. 



First Instar. 



Size. Length, 1.09 mm.; width of body, 0.65 mm.; width of head, 

 0.494 mm.; space between eyes, 0.299 mm. 



Shape. Flat, width of body greater than one-half the length. As 

 time for first molt approaches the body becomes thicker in dorso-ventral 

 line, a fact which holds for the other stages as well. 



Color. Eyes dark red, body mottled with smoky grayish-black. Pat- 

 tern distinct, as shown in pi. XXVII, fig. 7. Pattern about as described 

 for second instar, with the exception of mesothorax, where irregular 

 blotches of dark pigment replace the transverse arcuate bands described 

 below. 



Structural PeculiaHties. The limbs in this stage are proportionately 

 larger than in following instars. The stout hairs fringing the limbs 

 are not as definitely arranged for a given purpose as later. The fringe 

 of swimming hairs on hind limbs made up of few hairs. The middle 

 limbs, which in the adult are so slender and long, are thick and no 

 longer than the hind limbs. The femur is as long as tibia and tarsus 

 together, which are subequal. Tarsus is 1-segmented, and ends in two 

 long slender claws, which nearly equal the length of tibia and tarsus 

 together. 



Hind limbs not conspicuously flattened as in later forms, the swim- 

 ming hairs few, perhaps a dozen in each row, and confined to the tarsal 

 segment, which ends in a pair of almost spine-like claws. These claws 

 are about half the length of tarsus, and straight, save for a slight devia- 

 tion from a straight line at a point two-thirds the distance from their 

 base. 



The dorso-caudal side of hind tibia with an irregular row of 10 to 12 

 short, stout spines. A few other less conspicuous spines upon this seg- 

 ment and two longer ones on caudal margin of distal end of this seg- 

 ment. 



Middle Leg. Two short spines on anterior margin of femur, and two 

 long ones near distal end. Tibia sparsely covered with short, stout 

 hairs, a long one on anterior margin near base, two near distal end. 

 The marginal series of spines as delineated. 



Caudal Segment. Pair of short peg-like spines astride the median 

 line. Caudo-lateral angle of body with five pairs of long spines, 

 cephalad of which are two short ones. The penult segmental margin, 

 12 long spines cephalad of which are two or three short ones. The ante- 

 penult segmental margin, a pair of subequal long spines and cephalad 

 of these two or three shorter ones. 



Second Instar. 



Size. Length, 1.638 mm.; width of body, 0.858 mm.; width of head, 

 0.65 mm.; distance between eyes, 0.364 mm. 



15 — Sci. Bui. — 1669 



