SURVIVAL OF IXODES-SCAPULARIS (ACARI, IXODIDAE) EXPOSED TO COLD

The cold hardiness of Ixodes scapularis Say unengorged larvae, engorge d larvae, unengorged nymphs, engorged nymphs, and unengorged adults wa s evaluated. Ticks were exposed to cold for 2 or 8 h at a range of tem peratures. Likelihood ratio tests and LT(50) estimates were used to ev aluate cold hardiness. Likelihood ratio tests indicated that stage and engorgement effects were significant with the exception of the stage effect between engorged larvae and engorged nymphs. LT(50) estimates i ndicated that unengorged nymphs were the most cold-hardy, followed by engorged nymphs, unengorged adults, and both unengorged and engorged l arvae. Sex of adult ticks had no statistically significant effect on c old hardiness. Unengorged larvae and unengorged nymphs were tested for evidence of a cold-hardening response. No larvae or nymphs exposed to a cold pretreatment and subsequent cold treatment displayed rapid col d-hardening.