61 



dragonfly life by several members of our Society, and also 

 by the Rev. A. East, who breeds annually a large number 

 of one of the larger species, yEsclma cyanca. His obser- 

 vations enable him to assert that normally this species 

 requires two years (not three, as was once thought) from the 

 laying of the eg^ to the assuming of the imaginal condition, 

 though very exceptionalh' growth seems to be delayed, and 

 three years are required. Whether as much as two years 

 is required for the smaller species is at present unknown. A 

 lucky accident enabled Mr. East to get some idea as to the 

 number of times the skin is cast by the nymph of the same 

 species. An isolated nymph lo mm. long was found with 

 three cast skins, the smallest being ^\ mm. in length. By 

 the time the nymph had attained a length of 20 mm. it had 

 cast seven more, and we shall doubtless be told next year 

 how many more are cast before the imago appears. We 

 next want to know how many skins smaller than the one 

 3J mm. long were thrown off. Recollecting that the egg is 

 about i^ mm. in length, we should hardly expect more than 

 one. But in this connection Mr. P. P. Calvert, a well-known 

 American writer on the Odonata, reminds us that the nymph 

 leaves the egg in an embryonic condition, the legs not being- 

 free, and that it changes its skin almost immediately. So in 

 all probability there were two ecdyses at least before Mr. 

 East began his observations. It is curious to note two 

 statements of Swammerdam, the Dutch naturalist, in 1680 

 about nymphs of dragonflies. He says in one place that 

 the "limbs come out of the egg imperfect," and in another 

 that he does not know how long the eggs are before they 

 hatch, nor how long the nymph stage lasts, but he thinks 

 two years are occupied by the latter. (I have made use of 

 Dr. Hill's English translation of Swammerdam's " Biblia 

 Naturae," published in i75<S.) 



By breeding a large number of specimens of the same 

 species Mr. East was able to find out that the two sexes are 

 produced in almost the same numbers, and that one sex is 

 never much before the other in the order of emergence. 

 Imagines were produced as a rule in the night. When ready 

 to fly they were set free, and they went straight away : but 

 a month or more afterwards a small fraction returned to the 

 pond to breed. Mr. East made some observations on 

 nymphs of more than one species kept, out of water, but 

 in damp air, and found that they suffered no apparent incon- 

 venience, although they were so kept without food for a 

 month at a time, and that they fed again readily when put 



