60 EEPOET 108, U. S. DEPARTMENT OF AGEICULTUKE. 



adhering to the membrane, which, alternately receding and bulging out, rolls the egc 

 back and forth on the capitulum so that it is completely covered by a viscid substance 

 secreted by numerous minute glands in the membrane. This operation is repeated 

 for each egg, the parent resting occasionally. Several hundred eggs may be laid in 

 one day, and as the eggs may number 3,000 or 4,000, it takes several days for the 

 deposition of the entire mass. 



This curious method of oviposition was first observed by Prof. Gene in 1844, and ha^ 

 been confirmed by many later observers. The period of incubation varies accordin_- 

 to the temperature, in some cases occupjdng only about three weeks, but usually 

 longer period. Eggs deposited in the fall will not hatch till the following spring. 



The young ticks, known as "seed ticks," often remain clustered for several days and 

 then ascend the nearest support of grass or herb and patiently await the coming ci 

 some animal. Delay and disappointment must often eiv'. 

 in starvation and death. The seed ticks, however, are abL 

 to endure long fasts, and many finally secure an attacli- 

 ment to some animal. After a few days of feeding th' 

 young tick becomes distended with blood and drops to th' 

 ground. Here it seeks a hiding place and rests from one t' 

 several weeks, during which time there are many change 

 in its internal anatom3\ Finally the skin splits and frci 

 the six-legged larva there issues the eight-footed nymplj 

 Climbing a plant, it awaits the passing of some suitabL 

 animal, and, when attached, feeds, and falls off again t<> 

 molt; this time to the adult condition. It again waits-foi- 

 a host, and finding one, feeds and starts the life cycle 

 anew. The Texas-fever tick, its allies, and a few othc ' 

 species do not drop off for molting, but cast the skin whil 

 Fig. 112.— Claws of Margaro- on the host. This enables a more rapid increase in th 

 UhitrrtrnT'" ^^^''^^°^'' species, and not as many die from failure to find a hosi 

 Several other ticks pass the first molt on the host, but 

 drop for the second. When the nymph drops it may be several months before ii 

 transforms, and the quiescent period is usually longer than in the larval transformation . 

 Ticks do not always leave upon the death of the host, but often die attached to th 

 animal. Temperature and moisture are the principal elements influencing their lii' 

 and most of them prefer a dry, hot climate. Two chalcid parasites have been bred 

 from ticks, and a number of birds sometimes feed upon them. Chance plays a leadinp: 

 part in their life. If the thousands of eggs laid by one female were to mature, in a f ew 

 generations one pair would be the parents of billions of ticks. The number of ticks 

 in nature remains about the same year after year, so it is e\'ident that only a few of the 

 possible millions ever reach maturity. 



In the true ticks there is a considerable difference between the sexes. In the 

 male the dorsal shield covers the entire dorsum, whereas in the female there is always 

 an exposed portion behind the shield. In several genera the male has corneous 

 shields near the anus, and in some cases the hind pair of legs are enlarged in the males . 

 the porose areas are found only in the females. The males and females feed side by 

 side, Ijut the younger stages are often restricted to a different part of the host or to ;i 

 different host than that attacked by the adults. In some cases two years may be 

 required for a tick to become mature; in others there are several generations a year; 

 in several species the young and adults are found on the host at the same tini( 

 Ticks have been known to remain on a host for over 200 days, but in many cases life 

 is shorter. Africa is the home of ticks. Nearly all of the known genera occur thcic 

 and more species than on any other continent. Several species occur quite far north, 

 but as a whole ticks are particularly tropical animals. 



Our country has a number of sjK'cies similar to the European ones, hui in tlie pr(\-^- 

 ence of Amhlyomma and the great abundance of Dermacentor our ixodid fauna differs 



