284 NATURE SKETCHES IN TEMPERATE AMERICA 



midges. May flies, and other aquatic insects that preyed upon 

 their neighbors. Regarding this stream, Needham says : 



"The pools are the home of the Cordulegaster nymphs (C. 

 ohliquus). They lie on the bottom covered with silt. They 

 do not burrow, but descend into the silt by raking it out from 

 beneath with their legs. Then, when deep enough, they kick 

 it up over their backs and hide themselves absolutely against 

 observation, having only the sharp, upper angles of the eyes, 

 the sensitive antennae and frontal fringe, and the respiratory 

 aperture at the top of the abdomen exposed. Thus they lie 

 in ambush, wholly inactive, unless the wandering near of some 

 May fly nymph (here Leptophebia parpedita Etn.) or gnat 

 larva invites a thrust of the enormous, grasping labium. They 

 have competition for their food, also dwelling in the pools, 

 chiefly the red-bellied minnow and black-nosed dace." 



The active red-belUed minnows, Chrosomus erythrogaster, 

 make very good aquarium objects for study. On the day 

 mentioned above, I obtained several individuals of this species, 

 which lived in an ordinary aquarium in my home for a period 

 of a year. After five years one of these minnows is still alive. 

 The rest of them, at different times since first confined, jumped 

 out of their small quarters onto the floor during my absence. 

 This species of minnow is more or less of a vegetable feeder, 

 consuming green algse in quantities, its choice of these plants 

 being Spirogyra, which is abundant in almost all our ponds and 

 streams. In situations of the brook, such as I have shown, 

 earth worms and midges, the latter in either larva or adult 

 stages, also form a large proportion of theiV food. 



If any of our readers desire a handsome species for stocking 

 a pond, or for aquarium objects, this is certainly a most desirable 

 native species to cultivate. In the spring at the time of mating, 

 the males undergo a change of color of a secondary sexual 

 character. The sides of the abdomen, which are ordinarily 

 silvery white with a dark stripe, become suffused behind the 

 gills backwards, with an exquisite, brilliant Fed. 



Nature's Laboratory 



The great laboratory of nature is always .open to the interested 

 observer. On the one hand, we see the effect on animal and 



