SOME HUMAN PARASITES 281 



seven to ten days. When first hatched the young are quite 

 white and nearly transparent, becoming straw-coloured after 

 several hours, and except in colour and the absence of wing 

 pads they somewhat resemble their parents (see fig. 79, A). 

 After the first full meal of blood their bodies become red, 

 except for the head, thorax, legs, and extreme tip of the 

 abdomen. Five moults occur before the adult stage is 

 reached, and the wing pads appear with the last moult. A 

 single full meal is always taken before the skin is shed, so 

 that in the seven to eleven weeks occupied in attaining 

 maturity the young bed bug feeds five times, and although 

 the time taken to grow up may be protracted, owing to 

 lack of food or a low temperature, the number of feeds 

 remains the same. Another full meal is taken by the 

 female before ovipositing, in fact it is the almost invari- 

 able rule that insects, and allied animals, which feed on 

 blood are quite incapable of laying fertile eggs till they 

 have become engorged. 



We have seen that the normal food of the bed bug is 

 human blood, but these insects have been fed artificially 

 on mice, English sparrows, guinea-pigs, and the North 

 American mole. Like all animal parasites, the adults can 

 exist for almost incredible periods without food specimens 

 have been kept foodless for over a year, without apparent 

 injury. This wise provision of nature, which reaches its 

 greatest pitch in some of the ticks, is of the greatest import- 

 ance to the insects concerned, for it is obvious that suitable 

 food may not always be forthcoming. Disgusting as the 

 bed bug is in its habits, it is endowed with an even more 

 disgusting smell, arising from a clear, oily liquid secreted 

 by glands situated between the legs. This secretion, 

 common to many of the Rhynchota, is probably protective 

 against insectivorous birds, though in our subject it is of 

 little avail against cockroaches and ants, both of which 

 devour the bed bug with avidity. 



America is blessed with an inveterate enemy of the bed 



