DRAGONFLIES AND DAMSEIvFUES IN PONDFISH CUI.TURE. 



225 



Ischnura and Knallagma among the damselflies and Leucorrhinia among the 

 dragonflies seem particularly susceptible to these mites. Ten or a dozen of the young 

 mites were found between the wing pads and around the bases of the legs on each of 

 five Ischnura and seven Enallagma nymphs. Forty-four of them were taken from 

 the ventral surface of the thorax of a single female imago of Enallagma hageni and 

 no were removed from the ventral surface of the abdomen of a single male imago of 

 LeiA£orrhinia intacta. Tillyard said that the young mites cling to the dragonfly without 

 doing it any harm, but in this Leucorrhinia the considerable surface covered by the 

 mites was badly discolored, being changed from black to a yellowish red. The points 

 where each mite was attached were also somewhat swollen and deep red in color, so that 

 the integument seemed to be honeycombed. So far as this particular specimen was 

 concerned, the mites had been obtaining sustenance as well as transportation. 



In the family of flies known as Asilidae there are two genera, Promachus and 

 Lophonotus, which have been seen to capture and eat dragonflies (Poulton, 1906, p. 

 342). 



6. InTERNAIv Parasites. — ^The imagos are susceptible to intestinal parasites as 

 well as the nymphs, and Selys-Longchamps (1850, p. 36) recorded the finding of a Filaria 

 in the abdomen of a dragonfly which inflated it to such an extent as to hinder the 

 insect's flight. 



Ssinitzin (1907, p. 24) reported stages of a frog-lung fluke, PneumonoBces varie- 

 gatus, free in the body cavity of both nymphs and adults of the damselfly Agrion 

 (Calopteryx) virgo. By feeding experiments he was able to infect frogs with these 

 forms, showing that the damselfly here serves as an intermediate host for the frog fluke. 



7. Sundew and Pitcher Pi^ants. — An observation of Tillyard's (191 7, p. 329) 

 is worthy of mention here. He said that in Australia the giant sundew, Drosera binata, 

 takes heavy toll of those damselflies which frequent the swamps and marshes. It is 

 doubtful whether any of our North American sundews are capable of capturing dam- 

 selflies, but our pitcher plants certainly are, and it would be interesting to know if 

 some of them do not occasionally claim odonate victims. 



ODONATE NYMPHS AS FISH FOOD. 



Evidence from Fish Bait. — The first and most obvious proof that nymphs make 

 good food for fish is the fact that they are used successfully for fish bait. Tillyard 

 (191 7, p. 337) recorded that the larvae of Hemicordulia, called appropriately by the 

 Australians mud eyes, are much sought after as bait for trout and perch. Needham 

 (1903, p. 212) said: "Nymphs attached to hooks were taken by trout, but not more 

 readily than minnows, small frogs, or other bait." He could also probably have said 

 with equal truth that they were not taken any less readily than other bait. 



Fishermen in certain parts of the country use nymphs regularly as bait in the 

 same way that "dobsons" are used for bass bait. In Michigan and Minnesota the 

 nymphs are locally called "crabs," and it is said that the rock bass or redeye will take 

 them when it refuses other bait. In the vicinity of Torrington, Conn., the nymphs are 

 known as "perch bait," and boys make a business of catching and selling them to the 

 fishermen. But, of course, the best proof that nymphs serve as fish food is the fact 

 that they are found in goodly numbers whenever the stomach contents of fishes are 

 examined. 



