42 THE DURATION OF LIFE. 



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, which sometimes appears in 

 countless numbers, states that ' six weeks after (such a swarm had 

 been first seen) they had all disappeared.' Hildreth 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, 'Naturgeschichte,' 2 ter Bd. 3* Abth. p. 1588 et seq.). 

 Acanthia lectularia. No observations have been made upon the 

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

 tained, 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 or- 

 gotten : 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 ob- 

 served 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 33C : 

 they 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 ter Bd. 3* Abth. p. 1613.) 



V. DlPTERA. 



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 of sucking 

 blood is given them.' The length of time which intervenes between 

 the emergence from the cocoon and fertilization or the deposition 

 of eggs is not stated. 



Sarcophaga carnaria. The female fly dies ten to twelve hours 

 after the birth of the viviparous larvae ; the time intervening 



