Fig. 2._Haemaphysalis leporis-palustris, continental rab- 
bit tick, unengorged adult female. This tick is a vector of tu- 
laremia. The characteristic of sharply pointed, lateral angles 
near the base of the mouthparts (one indicated by arrow) is 
distinctive of this tick in all stages. 
homa, Missouri, Iowa, Montana, and Minnesota, is not 
equally abundant on rabbits at all seasons, and, further- 
more, one or more of the stages are often rare to absent 
at certain seasons. Even in Florida the continental 
rabbit tick is noticeably less abundant in winter (Ilixon 
in Eddy 1942). 
Apparently the more northerly the region the more 
markedly the populations of this tick fluctuate on rab- 
bits with the seasons. In Oklahoma (Eddy 1942) and in 
southern Missouri (Portman 1944), this tick occurs 
occasionally on rabbits even in midwinter. By contrast, 
in northern Missouri (Portman 1944), Iowa (Joyce & 
Eddy 1943), Montana (Cooley 1932), and Minnesota 
(Green et al. 1943), it becomes scarce on or entirely 
absent from rabbits during the coldest winter months. 
In Minnesota, Green et al. (1943) found that larvae 
of Haemaphysalis leporis-palustris ‘‘suffer a relatively 
enormous loss as compared with the losses among older 
ticks, and that the total winter mortality can be ac- 
counted for largely on the basis of deaths of larval 
ticks.’’ In Iowa, Joyce & Eddy (1943) reported an abrupt 
decrease to very few larvae on rabbits in November, an 
absence of larvae in December, and a low prevalence of 
larvae on rabbits in April, May, and June. Apparently 
in Iowa, as in Minnesota, many unfed larvae fail to 
survive the winter. 
Hooker et al. (1912) observed that under favorable 
conditions ticks in the larval stage could survive as 
long as 258 days (about 8 months) without feeding. They 
found, however, that most larvae survived for 2 to 7 
months. 
In this study, we found that continental rabbit ticks 
came out of hibernation earlier in southern Illinois than 
in Lee County. An observation of winter activity was 
made by Glen C. Sanderson in Union County, southern 
Illinois. There he found, on December 21, 1955, an adult 
rabbit tick feeding on a swamp rabbit, Sylvilagus aquat- 
icus aquaticus (Bachman). In southern Illinois, adults 
appeared regularly in some abundance on rabbits at the 
end of January. Our earliest records of the year for 
rabbit ticks in Lee County were of adults collected on 
February 25, 1953, and February 17, 1954. 
When the warmer weather of spring arrived, increas- 
ing numbers of both adults and nymphs of the continental 
rabbit tick were found attached to rabbits in Lee County, 
fig. 4. By mid-April copulating pairs were observed on 
their hosts. By July the numbers of adults had decreased. 
Adults seldom were found on rabbits in Lee County in 
autumn or the first part of winter. Only one adult was 
found on these rabbits in fall. This specimen was taken 
on November 9, 1954. Although rarely on rabbits in 
autumn and winter, adults were present in the surround- 
ings and were taken repeatedly in September, October, 
and November from leaf mold. 
During the several winter and spring months in 
which we examined rabbits for ticks in Lee County, we 
found no larvae of the continental rabbit tick. We learned, 
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Fig. 3.—Haemaphysalis leporis-palustris distribution in 
Illinois, based on Illinois Natural History Survey records. 
vu 
