October, '11] WOOD: TICK parasites 427 



Life History and Habits 



In describing the life history of the parasite, we shall start with 

 adults emerging from a small round opening at the posterior end of 

 the nymph. (See PI. 17, Fig. 5). The insects often encounter consid- 

 erable difficulty in getting out through the small passage way. Should 

 the nymph become somewhat dry, it occasionally happens that the 

 parasites are unable to emerge. As soon as the male has extricated 

 itself, it immediately seeks a female. Once free, the female awaits 

 the male, meanwhile preening her antennae and wings with her fore- 

 legs. The male rapidly fertilizes the females, the sexual act requiring 

 but a few seconds. As soon as she is fertilized the female starts off 

 hastily in search of her victim. To the tick larva the parasite pays 

 no attention; but attempted oviposition has been observed in both 

 a male and unengorged female of R. sanguineus. All that the parasite 

 requires is a nymph at least partially engorged. In nature both 

 nymphs on the ground or on the host seem to be attacked. On 

 the host animal the tick parasite is perfectly at home crawling through 

 the hair as naturally as a flea. A nymph which has become quiescent 

 before molting seems to be in no danger from the parasite. It ap- 

 pears to delight in motion on the part of its victim. When crawling 

 about on the tick host, the parasite makes little use of its wings, but when 

 free the insect moves about in short flights. Often the parasite will in- 

 sert its ovipositor immediately after reaching the nymph, but some- 

 times it takes a few seconds of examination and at other times longer. 

 After inserting its ovipositor, which remains inserted from about two to 

 twenty seconds, the parasite usually leaves its host and seeks another 

 victim. It may, however, wait and insert its ovipositor again, but never 

 has been observed to oviposit more than twice in the same tick. 

 Although feeding is not necessary before oviposition, this parasite 

 has been seen to imbibe sweetened water when offered the chance. 



In from eight to fifteen days in October the characteristic striped 

 appearance (See PI. 17, Fig. 12) of the parasitized nymph becomes evi- 

 dent. In about forty-four days during October and November, the 

 parasites emerged as adults. The parasitic period within the nymphs 

 is very nearly the same as the molting period of the nymphs. 



A study of the accompanying table (No. 1) will give some idea 

 as to the number of parasites per tick, the proportion of sexes ^ and 

 the time spent by the parasite within the nymph. 



» The sexes are easily distinguished by the difference in the antennae. The 

 segments of the antennae of the female are broader than long with the end seg- 

 ment club shape, while in the male the segments are longer than broad, the end 

 segment being the same width as the others. Compare PI. 17, Figs. 3 and 4. 



