110 PROCEEDINGS ENTOMOLOGICAL SOCIETY 



genus Argas have generally been supposed to pass three ecdyses 

 before arriving at the sexually mature stage. This has been 

 reported by Lounsbury to be the case with Argas persicus, the 

 South African fowl tick, the habits of which appear to be 

 identical with those of our fowl tick, Argas ininiatus. The 

 structure of these two species is so much alike that Nuttall and 

 Warburton, in their recent monograph of the Argasidse, have 

 considered ininiatns a synonym of persicus. In breeding experi- 

 ments u'itli ininiatus I have found that something like one- 

 fourth of the individuals bred to maturity, under similar con- 

 ditions, hare an e.rtra or tliird nymphal ecdysis, making a total 

 of four ecdyses during their life. This is not a sexual varia- 

 tion, as both males and females were among those which molted 

 a fourth time before the external sexual characters appeared. 

 Neither is it due to a difference in the food supply, as all of 

 the ticks were well engorged, nor to climatic conditions, since 

 it occurred under exactly the same conditions as were furnished 

 the other ticks. It has occurred in broods bred during the fall 

 and winter and during summer. The engorgement of blood, 

 in each instar, before the following ecdysis can take place, 

 necessitates an exposure to the danger of discovery by the fowl, 

 mouse, or other enemy, or to injury in other ways. It thus 

 appears that the three-molt habit is most advantageous, since 

 but four instead of five engorgements are necessary before 

 reproduction can commence. A much greater advantage is 

 gained than is at first apparent, since it is in the more mature 

 stages that the exposure to danger in the search for the host is 

 greatest. These three-molt ticks may perhaps be considered 

 as descendants from a mutant which, through the process of 

 natural selection, have now come to predominate. On page 121 

 of Volume TIT of the Proceedings of this Society, Dr. C. V. 

 Riley states that he knew a specimen of Argas rejlcxus to re- 

 main alive in a corked vial without food for some five years, 

 molting repeatedly during the period. The statement, however, 

 both as to the period of longevity and number of molts, still 

 remains to be substantiated. 



It is well known that in some insects the number of molts 

 may vary, an excessive number at times being clue to some 

 physical cause, such as a lack of food combined with low tem- 

 perature or to a partial starvation. This has been considered 

 by Packard as due to the hypodermal cells retaining their 

 activity. Packard has reviewed the literature on the number 

 of molts in insects in his Textbook of Entomology, pages 615- 

 618, but cites no case in which a variation occurs when similar 

 amounts of food and climatic conditions are supplied. 



