NO. 7 PROTECTIVE ADAPTATIONS — McATEE 29 



aquatic hemiptcra, salamanders, frogs, turtles, and many kinds of 

 fishes prey upon the nymphs. Ants, spiders, robber flies, chipmunks, 

 snakes, frogs, toads, and fishes feed to some extent also on adult 

 dragonflies, obtaining most of them no doubt when teneral. They are 

 parasitized by nematodes, mites, and flies.' 



Discussion. — Odonata, both immature and adult, are freely preyed 

 upon by a variety of enemies and no special defense can be assumed 

 except the great expertness in flight of some of the dragonflies. This 

 we have seen does not foil various birds nor of course predators from 

 tlieir own ranks. All in all it would seem that Odonata are preyed 

 upon fully in proportion to their abundance. 



AGNATIIA (mayflies) 



Protective adaptations. — The nymphs that live in water are plainly 

 colored ; some cling closely to various objects in their environment, 

 while others swim in a rapid darting manner. The adults also are 

 usually inconspicuously colored. 



Bird enemies. — Our tal)ulation shows mayflies to have been identi- 

 fied from the stomachs of 108 species of nearctic birds. A nighthawk 

 has been known to contain 400 adults at one time or many thousands 

 of eggs, the remains of the digestion of adults. x-\s many as 250 

 nymphs have been found in a godwit's stomach. Mayflies periodically 

 are exceedingly abundant and then are preyed upon by practically all 

 kinds of insectivorous birds. An interesting account of the behavior 

 of birds in the presence of a swarm of ephemerids is given by Dr. S. D. 

 Judd in his " Birds of a Maryland Farm " ; ' on this occasion 40 

 species of birds were observed eating mayflies. This list adds nine 

 to the species of birds known from stomach examination to feed 

 upon mayflies. 



Number of identifications, 484 ; percentage of identifications among 

 those of all insects, .2535 ; percentage of species in this group among 

 the whole number of insect species known, .1041. 



Other enemies. — Mayfly nymphs are eaten by the nymphs of stone- 

 flies and dragonflies, by water bugs, most fresh-water fishes, and to 

 some extent by salamanders and turtles ; the adults are preyed upon 

 by fishes and adult dragonflies, spiders, toads, and bats. 



Discussion. — Mayflies are good food for predacious animals and are 

 eaten freely, so much so as to cause David Sharp to remark : ' " That 



^ For full discussion of dragonfly enemies, see Bull. U. S. Bur. Fisheries, 

 vol. 36, pp. 209-211 and 222-232 (1917-18), 1920. 

 ^Bull. 17, U. S. Biol. Survey, pp. 22-24, 1902. 

 ° Cambridge Nat. Hist., vol. 5, p. 442, 1910. 



