Taylor’s Checkerspot (Euphydryas Editha Taylori) Oviposition Habitat Selection and Larval Hostplant use in Washington State

Taylor’s checkerspot (Euphydryas editha taylori (W.H. Edwards 1888)), a Federal Endangered Species Act candidate species, is found in remnant colonies between extreme southwestern British Columbia and the southern Willamette Valley in Oregon. This butterfly and its habitat have declined precipitously largely due to anthropogenic impacts. However, this butterfly appears to benefit from some land management activities and some populations are dependent on an exotic hostplant.

Oviposition sites determine what resources are available for larvae after they hatch. Larval survival and growth on three reported hostplants (Castilleja hispida, Plantago lanceolata, and P. major) were measured in captivity to determine the suitability of hostplant species and to develop captive rearing methods. Larvae successfully developed on C. hispida and P. lanceolata.

Parameters of oviposition sites were measured within occupied habitat at four sites in Western Washington. Sampling occurred at two spatial scales with either complete site censuses or stratified systematic sampling on larger sites. Within the sampled or censused areas, oviposition sites were randomly selected for paired oviposition/adjacent non-oviposition microhabitat measurements.

Taylor’s checkerspot oviposited on all reported perennial hosts available. Oviposition was significantly associated with high hostplant density at three of four sites. All but one of 31 oviposition locations selected for microhabitat measurement contained >10,000cm3 hostplant volume within 1m2 surrounding oviposition sites. Other habitat factors examined were suggestive but not statistically significant as influencers of oviposition perhaps because only occupied habitats were measured and thus they were de facto broadly suitable for checkerspot use.

The consistent preference for high density hostplant patches indicates that assessments of habitat and restoration objectives should weight high density hostplant areas more heavily than mean site level host plant abundance or cover and that, within areas of broadly suitable grassland vegetation structure, sites containing high densities of hostplants can be found and used for oviposition.