28 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 85 



ODONATA (dRAGONFLIES, DAMSELFLIES) 



Protective adaptations. — Dragonflies are fairly large, powerful, 

 predacious insects with remarkable ability for flight. They are 

 held in fear by illiterate people, a feeling possibly inspired by the 

 large mobile head consisting chiefly of eyes, and the strikingly con- 

 trasted color-pattern of many of them. A dark ground color with 

 vivid spots of green or yellow, answering to the description of warning 

 color, is common among dragonflies ; some also have brilliant red, 

 blue, and metallic colors. 



On the other hand, members of the order known as damselflies in 

 general are weak on the wing and of slighter and more delicate 

 structure. Some of them also are brightly colored but many are 

 dull. The immature stages of both dragonflies and damselflies are 

 aquatic, and predacious, and invariably inconspicuously colored. 



Bird enemies. — It might perhaps be expected that damselflies would 

 be more frequently captured by birds than dragonflies, but this does 

 not seem to be the case, the determinations for these groups so far 

 standing at 245 damselflies and 707 dragonflies. However, 2,082 

 identifications do not indicate which suborder is concerned. About 

 200 species of birds are known to eat Odonata, and nymphs as well as 

 adults are freely taken. No fewer than 100-125 nymphs have been 

 taken from the gullet and gizzard of individual ducks, yellow-legs, and 

 magpies. Regarding the adults, Needham says : " It is doubtful 

 whether anything that flies is able to capture in flight one of the 

 swiftest dragon flies." ' However, we have records of birds eating 

 Epiaeschna heros, one of the largest and swiftest of the dragonflies of 

 the United States, and Anax Junius, another of the giant species, is 

 commonly eaten by the pigeon hawk. No fewer than 28 individuals 

 of Anax were found in a single stomach of this falcon, and adult 

 dragonflies, mostly Anax Junius, were found in 120 out of 181 

 stomachs of the species. In a lot of dragonfly wings, picked up under 

 the home of a colony of purple martins at West Chester, Pa., were 

 represented about 63 individual dragonflies, largely Epiaeschna heros, 

 but including also, Anax Junius, LibcUula pulchcUa, and Anax 

 longipes. 



Number of identifications, 3,034 ; percentage of identifications 

 among those of all insects, 1.5891 ; percentage of species in this group 

 among the whole number of insect species known, .5986. 



Other enemies. — Odonata are notoriously cannibalistic both in the 

 nymphal and adult stages. Diving beetles, water scorpions and other 



' In Ward and Whipple, Fresh-water biology, p. 890, 1918. 



