before adulthood. He noted that most males appear at the fifth 

 molt, most females at the fifth or sixth molt, Jobling (1925) 

 and Pierquin and Niemegeers, however, observed no more than five 

 molts and foimd the majority of male emergence at the fourth molt 

 and the majority of female emergence at the fifth molt. Dr. G. 

 E, Davis* unpublished records show that in his laboratory most 

 females rea^h the adult stage at the fourth molt,* Discrepancies 

 in findings among various careful observers of this subject sug- 

 gest an interesting field for research, J^See also the section 

 on symbiotes and growth- promoting substances, page 177 ._7 



The interval between successive nymphal molts depends on the 

 time of the preceding blood meal not on the time of the last molt. 

 This is agreed by all workers. First instar nymphs require a 

 longer period before they are capable of feeding (three to twelve 



*It should be noted that while argasids have several nymphal iru 

 stars, ixodids molt directly to adults from the nymphal stage, 

 Ixodids remain on the host for several days in each, stage and ac- 

 commodate the huge volume of ingested blood by slow cuticular 

 growth (whether this is true for all ixodids, as for instance males 

 of several l-ladagascan haemaphysalids, should be investigated; cf» 

 Hoogstraal 195 3E), Argasids, on the other hand, feed much more 

 rapidly ajnd accommodate the volume of fluid ingested by stretching 

 the skin. Lees (1952) believes that this feature necessitates the 

 several nymphal instars of argasids. The rapid feeding of argasids 

 on animals that are usually resting reduces the danger of their 

 transportation under inclement conditions and to unfavorable envL- 

 ronnentsj they normally remain in handy feeding range in the host's 

 house, bvirrow, den, or lair. Lees cites the several blood meals 

 that a female argasid may take to nourish several egg batches as 

 an adaptation to maintain her fecundity. Female ixodids, which 

 take only a single, extended meal as adults, oviposit only once 

 over a period of several days. It is well known that ixodids de- 

 posit huge numbers of eggs but argasid eggs are relatively few in 

 number. This discrepancy, however, is overcome by the more favor- 

 able environment for obtaining a host in which argasid larvae and 

 nymphs usually find themselves. Survival of argasid populations 

 does not depend on large numbers of eggs but it does in ixodids. 



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