210 THE UNIVERSITY SCIENCE BULLETIN. 



tents. The pulsations of the dorsal vessel can also be seen in this 

 instar under the same conditions as before, save that the yolk is, of 

 course, totally gone." 



Third Instar. 



Size. "Length, 4.8 mm. ; vi^idth, 3 mm." 



Fourth Instar. 



Size. "Length, 6.5 mm.; w^idth, 4.2 mm. 



"Coloration and other peculiarities slightly more accentuated than in 

 the preceding instars. I may here state that just previous to a molt the 

 insect is very thick through, especially so in this and the succeeding in- 

 stars, and looks fit to burst out of its skin, as it does." 



Fifth Instar. 



Size. "Length, 8.3 mm.; width, 5.5 mm. 



"I was fortunate enough to have the opportunity of observing the last 

 moult in Pelocoris, which I will now describe from my notes taken during 

 the process of the ecdysis. 



"The bug hangs from the surface, back up. The outer skin then splits 

 along the thorax, and the scutellum of the emerging insect is seen. 

 The opening enlarges as the insect gives rhythmical convulsive heaves. 

 First the entire thorax comes out; then, with a jerk, the head. It now 

 rests a moment, and in a short space again takes up its motion, withdraw- 

 ing the body little by little from the cast-off skin. The dorsum, as yet 

 uncovered by the still unexpanded alse and hemelytra, has a coat of air. 

 The wings and hemelytra expand as the insect emerges, so that by the 

 time it is entirely out they are fully developed, completely concealing 

 the dorsum abdominis. It takes the insect about ten minutes to go 

 through this final transformation. When it is entirely free, it turns 

 quickly and hangs back down from the air-filled and buoyant cast skin 

 for a moment, until the wings are perfectly expanded. Then it begins 

 to swim about quite rapidly, coming to a rest once more, seemingly re- 

 quiring something to hang to. There appears to be an undue amount of 

 air under the insect's wings while it is in this condition, and it remains 

 back up while swimming. The tracheal lining may be seen as Pelocoris 

 emerges, connecting the sternum with the cast skin. 



"Pelocoris, immediately after the last ecdysis, is entirely of a beautiful 

 light green-like aquamarine, including the hemelytra and the limbs 

 excepting the tibiae, which are dark from the swimming hairs. The 

 eyes are a dark ruby-red. The insect gradually grows darker, and 

 about four hours after the change it is a mottled dark green. The full 

 mature coloration is reached in about 12 hours." 



Siimmary. Bueno has presented the only account of the rearing of 

 any Naucorid. The eggs of Pelocoris femorata were placed upon sub- 

 merged plants. They hatched in about 24 days. The first instar lasts 

 about 8 days; the second instar, 6 to 9 days; third instar, 8 days; fourth 

 instar, 10 to 12 days; fifth instar, 16 days. A total, as Bueno tells us, 

 of some 77 days for development. Nearly all stages may be taken in the 

 summer time in a pool. At Coldwater, Kan., in July, all stages but the 

 egg were noted. 



Family CORIXID^. 



A. Taxonomy of Corixid^. 



Family Characteristics. These medium-sized to small bugs are usually 



marked with bars of yellow and brown. The body is flattened above, and 



the head overlaps the thorax dorsally. The most peculiar thing about 



them is the structure of the beak, which is very short, scarcely if at all 



