228 THE UNIVERSITY SCIENCE BULLETIN. 



Structural Peculiarities. Wing-pads now long, reaching to the second 

 abdominal segment. The hind tarsus is still 1-segmented, and claws re- 

 duced. The tibial comb of hind tarsus is composed of longer spines than 

 before. The neutrality of the caudal segments of the nymph, in contrast 

 to those of the adults, is illustrated in the drawings on plate XXVTI, A 

 study of specimens killed while emerging shows the marked transforma- 

 tion that takes place between nymph and adult. The antennae of nymph 

 are heavy blunt-tipped appendages, plainly 2-segmented, with a con- 

 striction on the distal segment that may indicate that it is divided into 

 two segments. See drawing on plate XXVII. 



Behavior of Adults There are some points in the economy of the 

 lives of these insects worth noting. It is one of the very few water 

 insects overwintering as a nymph. In fact, the only one known to the 

 writer. For some time it was not clear as to why there should be this 

 exception. It seems, however, that since the species seldom, if ever, flies, 

 but lives in permanent waters, there is no occasion for the annual fall 

 and spring migrations indulged in by other species. Most Corixids fly to 

 larger pools to winter and in spring fly back to repopulate the shallower 

 ones. 



The adults of this species are given to burying themselves in the floc- 

 culent ooze on the bottom of the pool, and are thus difficult to locate. In 

 common with other species, they come to the surface for air, and if in 

 water of any depth are likely to head downward from the surface, swim- 

 ming in a spiral to the bottom. 



In accounts dealing with the stridulation of the male Corixids it is 

 stated they make their music at night. Some of these which were brought 

 into the laboratory surprised us with their chirping one cloudy afternoon. 

 Their stridulation was distinctly audible across the room and sounded 

 somewhat like that of distant crickets, save that the chirps came forth 

 in couplets. 



Sutnmary. The species here discussed winters as a fourth instar 

 nymph, reaches the adult stage about the first of June, and after a matur- 

 ation of eight days begins oviposition. This generation becomes adult 

 during August and starts the generation that overwinters as nymphs. 



The species is capable of living in great numbers in a pool. The 

 nymphs have been seen to strip the chlorophyll from filaments of Spi- 

 rogyra and an examination of the stomachs of many of them shows that 

 they consume quantities of living chlorophyll from the lower plant or- 

 ganisms that make up the flora of the pool bed. This herbivorous ten- 

 dency reduces the uncertainty of food getting and accounts in a measure 

 for their success. It has further been demonstrated that they can 

 complete their life cycle by foraging upon a flocculent mass of ground 

 Typha and its attendant population. 



The facts above presented, when combined with the lack of functional 

 wings, suggests the practicability of rearing them artificially. Since the 

 nymphs of this species have been recovered from the stomachs of fishes, 

 it may be that this form, easy to manipulate, can be utilized in increasing 

 the food supply for young fish. 



