REDUCED LONGEVITY OF DERMACENTOR-VARIABILIS AND IXODES-SCAPULARIS (ACARI, IXODIDAE) MOLTING FROM IMMATURES FED ON RATTUS-NORVEGICUS

Nymphal and adult Dermacentor variabilis (Say) molting from larvae and nymphs, respectively, that fed on a Holtzman strain of Rattus norvegi cus demonstrated reduced longevity compared with those from immature s tages that fed on albino laboratory mice, Mus musculus. The decrease i n survivorship did not appear to be caused by Lost-acquired resistance ; lower feeding weights, longer feeding times, and reduced molting wer e not observed. In addition, reduced survivorship was not limited to t icks fed on Holtzman rats. It was also demonstrated in adult D. variab ilis molting from nymphs that fed on Wistar strain rats, but the effec t was not as severe as with Holtzman rats. Moreover, reduced survivors hip occurred in Ixodes scapularis Say that fed on rats, but, again, th e effect was less severe than on D. variabilis. Nymphal feeding on mic e appeared to counteract the negative effect of larval feeding on rats in both adult D. variabilis and I. scapularis.