2o8 



BULIvETiN OF THE BUREAU OF FISHERIES. 



The first thing to be noticed is the general similarity in the food. The Hawaiian 

 nymphs ate mollusks, beetles, flies, bugs, Crustacea, odonates, and protozoa, the same 

 as the Fairport nymphs. Many of the food species were different, as would naturally 

 be expected, but they belong to the same families and sometimes to the same genera. 

 Unlike the nymphs at Fairport, those at Honolulu ate bees, ants, and adult Chiro- 

 nomids, mosquitoes, and flies. These land insects undoubtedly dropped into the 

 water before they were captured, and Warren has suggested that since the Hawaiian 

 streams and pools contain but few aquatic insects, while the dragonfly nymphs are 

 numerous in many localities, the latter must obtain a part of their food from land 

 insects that fall into the water. This idea induced him to try them with all kinds of 

 land insects, and he found they would eat anything he offered. (See p. 206.) 



Tadpoles also appear in their diet, probably due to the scarcity of insect food just 

 mentioned and also to the fact that the frogs and dragonflies are compelled to breed 

 in restricted bodies of water, so that they are brought into close contact. Another 

 result of the scarcity of insect food is that the majority of the nymphs fed upon a single 

 Chironomid species, Chironomus hawaiiensis, and upon the crustacean genus Cypris. 

 If the food had been more plentiful there would have been a greater variety in the diet. 

 Consequently the extreme variety in the food of the Fairport nymphs is a good indication 

 of the richness of the food supply. 



Food of Nymphs from Ithica, N. Y. — A table has been made out by Miss Lyon 

 (191 5) showing the food of 36 nymphs, distributed among 3 ^S^schnid species, 2 Gom- 

 phids, 4 Libellulids, and 4 damselflies. Cascadilla Creek, from which the nymphs 

 were obtained, flows along the southern border of the Cornell University campus at 

 Ithaca. The nymphs were collected at intervals from November to July, thus covering 

 nine months of the year. 



For the sake of convenience, her figures have been reduced to the same method 

 of treatment as used in the statement on page 201. 



Food Found in Alimentary Canal op 36 Odonatk Nymphs from Cascadilla CrBEk, Ithaca, 

 N. Y., Examined by M. B. Lyon. 



Mollusca: Physa, partly digested i 



Beetles: Dytiscus, sp 2 



Diptera: 



Chironomid larvae 24 



Mosquito larvae, Anopheles, sp i 



Undetermined larva i 



Hemiptera: 



Corixa nymphs 6 



Corixa adults . 2 



Ephemeridae: 



Heptagenia, sp 4 



Hexagenia, sp i 



Caenis, sp i 



Undetermined mayflies 2 



Crustacea: 



Hayalella, sp 5 



Diaptomus, sp 2 



Miss Lyon's investigations showed that while Chironomids, mayflies, and odonates 

 were eaten voraciously throughout the year, the Crustacea and Hemiptera were con- 



Crustacea — Continued . 



Cyclops, sp 2 



Cypris, sp 2 



Undetermined i 



Odonata: 



Libellulid, sp., nymph i 



Ophiogomphus, sp., nymph i 



Damselfly nymphs 9 



Arachnid: 



Mite . 2 



Macrobiotus, sp . "i 



Algae: 



Diatoms 5 



Closterium, sp 3 



CEdogonium, sp i 



