268 



Phylum Arthropoda 

 Order odonata 



CULTURE METHODS FOR THE DAMSELFLY, ISCHNURA 



VERTICALIS 



Evelyn George Grieve, Cornell University 



REARING work was begun with the full-grown nymphs which were 

 . collected early in the spring from a small, grassy fish pond. From 

 the first generation, which were the stock adults, eggs were obtained for 

 life history studies. As soon as the nymphs hatched they were isolated 

 and reared in separate containers for the entire life span. 



.. ,... c ....,,,, JiV , n Cages. The type of cage 



..:■•-* "'. '~> ""'"" N " ; If** j (Fig. 61) used for breeding 

 ^ f ->^M' :: .$£': /-'M stock was a fairly large 



aquarium covered with a 

 screen cage, fitting the 

 aquarium closely at the 

 sides, and allowing room 

 above for the adults to fly, 

 mate, and capture their 

 prey. Aquatic plants, prin- 

 cipally Eleocharis palustris, 

 were kept growing in one 

 corner of the aquarium; up 

 these the nymphs could 

 crawl to transform. When 

 the females were ready to 

 oviposit, one or two of the 

 flexible stems of E. palustris 

 were bent down into the 

 water where they were held 

 by the surface film. The 

 females preferred to 

 oviposit in these floating 

 stems, and each day eggs 

 could be removed and dated for the study of embryonic development. 



In order to keep records of all individuals, and also because the species 

 is cannibalistic, separate containers were used for all reared specimens. 

 The most satisfactory type for the young nymphs was a small boat 

 (Fig. 62 ) , floating with others in a large pan of water. The frame of the 

 boat is of balsa wood, which is very light and buoyant, and the "hold" of 

 the vessel is made of silk. Although the illustration of the boat is about 

 natural size, the silk was of finer mesh than that shown, namely about 



Breeding cage for Ischnura verticalis. 



