42 THE DURATION OF LIFE. [I. 



than the parthenogenetic females of the same species (Derbes, 

 ' Note sur les aphides du pistachier terebinthe,' 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 septemdecim, w^hich 

 sometimes appears in countless numbers, states that 'six weeks 

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

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

 to twenty-five daj^s. This agrees with the fact that the Cicada 

 laj^s 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, ' Naturgeschichte,' 2*^1- Bd. 3*^ Abth. p. 1588 et seq.). 



Acanthia lectitlaria. 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 liv^ely young ones. Goze found bugs in the hangings 

 of an old bed which had not been used for six j^ears : ' they 

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

 case, in which the starving animals were quite transparent. 

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

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

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

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

 ' Naturgeschichte,' 2*®^ Bd. 3*^ Abth. p. 1613.) 



V. DiPTERA. 



Pulex irritans. Oken says of the flea (' Naturgeschichte,' 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 



