42 THE DURATION OF LIFE. [I. 



than the parthcnogcnetic females of the same species (Derbes, 

 ' Note sur Ics aphides du pistachicr tercbinthe,' Ann. des sci. 

 nat., Tom. XVII, 1872). 



Cicada. In spite of the numerous and laborious descriptions 

 of the Cicadas which have appeared during the last two 

 centuries, I can only find precise statements as to the duration 

 of life in the mature insect in a single species. P. Kalm, 

 writing upon the North American Cicada septetiidecim, whicii 

 sometimes appears in countless numbers, states that 'six weeks 

 after (such a swarm had been first seen) they had all dis- 

 appeared.' Ilildreth puts the life of the female at from twenty 

 to twenty-five days. This agrees with the fact that the Cicada 

 lays many hundred eggs (Hildreth states a thousand) ; sixteen 

 to twenty at a time being inserted into a hole which is bored 

 in wood, so that the female takes some time to lay her eggs 

 (Oken, ' Naturgcschichte,' 2*^^ Bd. 3*® Abth. p. 1588 et seq.). 



Acanthia Icctularia. No observations have been made upon 

 the bed bug from which the normal length of its life can be 

 ascertained, but many statements tend to show that it is 

 exceedingly long-lived, and this is advantageous for a parasite 

 of which the food (and consequently growth and reproduction) 

 is extremely precarious. They can endure starvation for an 

 astonishingly long period, and can survive the most intense 

 cold. Leunis (' Zoologie,' p. 659) mentions the case of a female 

 which was shut up in a box and forgotten : after six months' 

 starvation it was found not only alive but surrounded by a 

 circle of lively young ones. Goze found bugs in the hangings 

 of an old bed which had not been used for six years : 'they 

 appeared white like paper.' I have myself observed a similar 

 case, in which the starving animals were quite transparc^nt. 

 De Geer placed some bugs in an unhcated room in the cold 

 winter of 1772, when the thermometer fell to — 33°C : they 

 passed the whole winter in a state of torpidity, but revived in 

 the following May. (De Geer, Bd. III. p. 165, and Oken, 

 ' Naturgcschichte,' a^^"" Bd. 3*« Abtii. p. 1613.) 



V. DiPTERA. 



Pulex irritans. Oken says of the flea (' Naturgcschichte,' Bd. 

 II. Abth. 2, p. 759) that 'death follows the deposition of the 

 eggs in the course of two or three days, even if the opportunity 



