Survival and Development of the Different Life Stages of Ixodes scapularis (Acari: Ixodidae) Held within Four Habitats on Long Point, Ontario, Canada

Abstract

From November 1989 to April 1993, blood-fed females and unfed adults and nymphs of lxodes scapularis Say were maintained in housings within 4 different habitats on Long Point, Ontario, Canada, to evaluate the effects of habitat on tick development. More fed females survived the winter within the maple forest (75.6%) than the cottonwood dune (36.1%), whereas 52.8-62.0% survived the winter within the 2 remaining habitats. The proportions of females that laid eggs within the maple forest (90.3%), oak savannah (83.9%), and white pine habitats (78.4%) were similar and greater than in the cottonwood dune (53.8%). In each habitat and all years, females began laying eggs during late April or early May. The time of egg deposition was consistent whether females fed in November and overwintered, or fed during April of the subsequent year. Significantly more eggs hatched within the maple forest (96.4%) and white pine (79.3%) than in the oak savannah (3.8%) or cottonwood dune habitats (0.0%). Hatch occurred in mid- to late July each year. The proportion of unfed I. scapularis adults that survived the winter was not significantly different among the 4 habitats. Unfed adults held in the oak savannah and cottonwood dune habitats died by early June, whereas ticks survived until late June or early July within the maple forest and white pine habitats. Unfed nymphs survived an average of 3.4 mo (range, 0.5-5.5) longer than unfed adults. Fed larvae placed in the field from 22 April to 3 July 1992 molted or died that year. In contrast, 66.7 and 100% of fed larvae placed in the field between 15 and 28 July, and after 28 July, respectively, overwintered before molting. More larvae successfully molted before overwintering (46.9%) than did those that overwintered (17.9%). The proportion of larvae that successfully molted was greatest within the maple forest and least within the cottonwood dune. Fed nymphs placed in the field from 22 April to 4 June molted or died in 1992, whereas 53.6 and 99.2% of fed nymphs placed in the field between 17 June and 28 July, and later than 28 July, respectively, overwintered before molting. Over all habitats, the proportion of nymphs that molted successfully was similar for those that overwintered (43.5%) and those that did not (36.0%). The proportion of nymphs that molted successfully was greatest in the maple forest (60.6%) and least within the cottonwood dune (13.3%). Differences in seasonal extremes of vapor pressure deficits among habitat types were likely responsible for habitat-specific differences in survival of I. scapularis. Based on observations on captive I. scapularis, the life cycle of this tick on Long Point is completed in 3 or 4 yr.

The Biological Survey of Canada: A Personal History

“…Throughout its range in Canada, I. scapularis likely requires 3-4 years to complete its life cycle (Lindsay et al 1998). Unlike the other human-biting ticks in Canada, unfed adults of I. scapularis begin active host-seeking in fall rather than spring.…”

“…Quiescence may be incomplete and adults can be collected in the winter months in parts of its range, or in certain years, when extended periods of snow cover or sub-zero temperatures are not experienced (Watson and Anderson 1976). Overwinter survival is variable but typically survival rates are highest for fed females followed by unfed females and males (Lindsay et al 1998). Adult activity declines following the April peak and adult cohorts rarely overlap because unfed adults do not survive later than August (Lindsay et al 1998).…”

“…Overwinter survival is variable but typically survival rates are highest for fed females followed by unfed females and males (Lindsay et al 1998). Adult activity declines following the April peak and adult cohorts rarely overlap because unfed adults do not survive later than August (Lindsay et al 1998). Adults (and nymphs) are frequently collected in deciduous or coniferous woodlands and from ecotonal (i.e., unmaintained edge) habitats (Maupin et al 1991), though these instars are also collected on lawns and ornamental shrubbery in suburban residential areas (Stafford and Magnarelli 1993).…”

“…Temperature influences, in a non-linear fashion, the duration of the pre-oviposition and oviposition period in I. scapularis (Ogden et al 2004). In field studies on Long Point, Ontario, regardless of whether females fed in the fall or subsequent spring, eggs were laid during late April and early May (Lindsay et al 1998). The number of eggs produced per female is dependent on engorgement weight and temperature such that females held at 12-28 °C produced 9034 ± 1706 eggs per gram of fed weight (Lindsay 1995).…”

“…Larvae hatch during mid-to late July (Lindsay et al 1998) and rarely actively disperse from egg masses (Stafford 1992), though this instar as well as nymphs can be carried great distances on avian hosts (Scott et al 2001;Morshed et al 2005;Ogden et al 2008b). Unfed larvae may feed during the year of hatch or overwinter without feeding and seek hosts the following year (Lindsay et al 1998).…”