AQUATIC INSECTS IX NEW YORK STATE 213 



I have not been able to determine as yet whether in relation 

 to trout culture Aeschna is more disadvantageous than other 

 wise. It eats a few of the fry and it eats the food of the larger 

 trout; but. on the other hand, it furnishes a moderate supply of 

 food itself for the larger trout. 



Out in the proper foraging ground of the trout, burrowing 

 shallowly under the silt of the bottom of the pond, are other 

 dragon fly nymphs of the genus Gomphus, which would seem to 

 be wholly detrimental. They feed voraciously on other insects 

 of the bottom fauna, and. doubtless, on Chironomus larvae, 

 while by their burrowing habits they seem to escape the trout 

 altogether. 



5 Callibaetis sp.? 



These nymphs, like the preceding, were found in an advanced 

 stage of digestion. That they were Callibaetis, however, was 

 determinable from the structure of the jaws, the top of the 

 thorax and the bases of the setae, which were preserved. Since 

 no adult May flies were collected at the pond and no nymphs 

 bred, what the species is could not be established. Cal- 

 libaetis f e r r u g i n a was taken at the hatchery, and the 

 nymphs may very well have belonged to this species.^ 



This is a large genus, peculiar to the new world. A consider- 

 able number of species are already described, and doubtless 

 many more will yet be discovered. I have found the nymphs ex- 

 ceedingly abundant in many small lakes and ponds. They are 

 most abundant amid the shore vegetation, but wander out into 

 ■deeper water, resting on the bottom, and darting rapidly from 

 place to place. 1 think it likely that they will be found more 

 important as the food of young fishes than of adults, because of 

 their greater abundance in the shallower water. 



It is due to the occurrence of a new species) of Callibaetis in 

 my campus pond at Lake Forest, where, with my students, I 

 have watched it year by year, that I am able to give some facts 

 respecting the genus, which have a bearing on its economic 



^ While this is going through the press there comes to my table a 

 descriptiou of the "nymph of this species with figures by Berry, in the 

 American XatiiraJist. 1903. 37:29. 30. 



