APPENDIX. 43 



between the exit from the cocoon and the birth of the young is 

 not given (Oken, quoting Reaumur, ' Mem. p. s. a 1'hist. Insectes,' 

 Paris, 1740-48, IV). 



Musca domestica. In the summer the common house-fly begins 

 to lay eggs eight days after leaving the cocoon : she then lays 

 several times. (See Gleichen, ' Geschichte der gemeinen Stuben- 

 fliege,' Nuremberg, 1764.) 



Eristalis tenax. The larva of this large fly lives in liquid 

 manure, and has been described and figured by Reaumur as the rat- 

 tailed larva. I kept a female which had just emerged from the 

 cocoon, from August 3oth till October 4th, in a large gauze-covered 

 glass vessel. The insect soon learnt to move freely about in its 

 prison, without attempting to escape ; it flew round in circles, with 

 a characteristic buzzing sound, and obtained abundant nourish- 

 ment from a solution of sugar, provided for it. From September 

 1 2th it ceased to fly about, except when frightened, when it would 

 fly a little way off. I thought that it was about to die, but 

 matters took an unexpected turn, and on the 26th of September it 

 laid a large packet of eggs, and again on the 29th of the same 

 month another packet of similar size. The flight of the animal 

 had been probably impeded by the weight of the mass of ripe eggs 

 in its body. The deposition of eggs was probably considerably 

 retarded in this case, because fertilization had not taken place. 

 The fly died on the 4th of October, having thus lived for thirty-five 

 days. Unfortunately, I have been unable to make any experiments 

 as to the duration of life in the female when males are also present. 



VI. LEPIDOPTERA. 



I am especially indebted to Mr. W. H. Edwards *, of Coalburgh, 

 W. Virginia, and to Dr. Speyer, of Rhoden, for valuable letters 

 relating to this order. 



The latter writes, speaking of the duration of life in images 

 generally : ' It is, to my mind, improbable that any butterfly can 

 live as an imago for a twelvemonth. Specimens which have lived 

 through the winter are only rarely seen in August, even when the 

 summer is late. A worn specimen of Vanessa cardui has, for 



1 Mr. Edwards has meanwhile published these communications in full ; cf. ' On 

 the length of life of Butterflies,' Canadian Entomologist, 1881, p. 205. 



