82 



of the nvinplis. In the above table nymphs Xos. 1 and 4 were 

 fed daily with larg'e amounts of food ; while Xos. 2 and 3 were 

 fed less often and in smaller quantities. The difference is 

 broniiht ont in that Nos. 1 and 4 completed their _c;rowth in 

 about two months, while Xos. 2 and 3 required over three 

 months for their develo])ment. 



Other experiments conducted aloni>' this line proved still 

 more strikingly the relation of food to growth. Two nymphs, 

 hatching on the sauie day, were placed in separate vessels. One 

 was fed liberally with mosquito larvae, and the other was given 

 five or six mosquito larvae every four or five days. In nineteen 

 days the former moulted seven times, and was well along the 

 eighth instar when the latter cast its third moult, and at this 

 stage was no larger than the other at its fourth instar. 



The ability to fast for long periods of time also plays a great 

 part in the length of nymphal life. Some experiments were 

 carried on to see how long nymphs could go without food. The 

 longest fasting periods, obtained in these experiments, were 

 from 14 to 1() days. Tender natural conditions, however, there 

 is no doubt but that they can keej) alive without food for much 

 longer periods. Some species of dragonfly nymphs have been 

 kept without food in confinement for a month and more. S]ieci- 

 mens of Aescliva cyanea and Agrion pneUa fasted for 30 and 33 

 days respectively ^Entomologist", 33:211), and at the end of 

 that time were still active and a])])arently not at all affected l)y 

 the long fast. 



From the above statements w(> may safely conclude then 

 that the nymphal period varies from two to six or more months. 



^idulf. — Xo attenqit was made to see how long the imago 

 lives, as the very active nature of the dragonfly and the manner 

 in which it procures its food would not j)ermit of any successful 

 feeding in confinement. It is reasonable to su])pose, however, 

 that its life does not extend over a great many weeks, if we can 

 draw any inference from the very advanced stage of develop- 

 ment of the ovaries in the later stages of the female nymphs, al- 

 though this is no definite proof, and experiments on the life of 

 the adult di-agonfly wouUl be of very great interest. In dissect- 

 ing nearly full-grown female nymphs, it was found that the 

 ovaries were full size, and the ovarian tubes practically as long 

 and plump as those of the adidt, but no signs of any eiji^g con- 

 structions could be detected. 



