Timing of Ixodes scapularis (Acari: Ixodidae) oviposition and larval activity in southern New York

Abstract

Timing of oviposition and larval eclosion for fall- and spring-fed female blacklegged tick, Ixodes scapularis Say, and effect of temperature on those events in southern New York state, where Lyme disease is endemic, were determined in the field. We also examined seasonal pattern of larval host-seeking activity, as well as rate of survival for overwintering, unfed larvae. Totals of 9 and 8 replete female I. scapularis were released in fall 1988 and spring 1989, respectively. For the 10 females that oviposited, egg laying began in mid-to-late May, regardless of when ticks had fed. Likewise, larval eclosion was synchronized in July for all egg masses. Microhabitat temperatures experienced by females were not reliable indicators of female reproductive success, in terms of either presence or absence of eggs, or numbers of larvae recovered. However, average body size was significantly greater for females that oviposited successfully than for those that did not. The percentage of unfed larvae surviving the 8-mo overwintering period from late August to early May ranged from 1.9 to 31.4, with a mean survival rate of 10.4%. Concurrent drag sampling through the year indicated a bimodal pattern of larval abundance marked by a relatively small early peak of activity in late May that extended into early July. Because the first peak of larval activity occurred during the period of oviposition, 8 wk before onset of larval eclosion, it appears that bimodality represents activity of 2 consecutive cohorts, with the early peak composed of overwintering survivors. These data imply variation in timing of reproduction and larval activity from 1 geographic area to another. Efforts to devise a comprehensive scheme for the life cycle of I. scapularis must consider that population differences may exist.