Ectoparasites of the Cottontail Rabbit 
In Lee County, Northern Illinois 
Of the wild animals in Illinois, the eastern cotton- 
tail rabbit, Sylvilagus floridanus mearnsii (Allen), is 
the species most commonly hunted and handled by 
human beings. Because rabbits are carriers of the viru- 
lent disease tularemia, which is transmitted from rabbit 
to rabbit by certain ectoparasites and from rabbits to 
men by handling, the ectoparasites of these animals 
are of considerable importance to human beings as 
well as to rabbits. 
A few years ago, ectoparasites of Illinois cotton- 
tails received limited investigation by Ecke (1948) and 
by Ecke & Yeatter (1956). About the same time, Yeatter 
& Thompson (1952) published an analysis of rabbits, 
their ectoparasites, and their diseases in relationship 
to weather and man. These studies served to bring new 
attention to the many gaps in knowledge of the seasonal 
activity and abundance of the ectoparasites of rabbits. 
When an opportunity arose in 1952 to make further 
observations on rabbits and their ectoparasites as part 
of a larger study of management of cottontails, a study 
designated as Project No. 42-R and set up under terms 
of the Federal Aid in Wildlife Restoration Act,t the 
authors joined forces in the hope that some new facts 
might be discovered that would fill one or more of these 
gaps. We realized that only part of our time could be 
devoted to this work and that our treatment necessarily 
would be brief. Principally, we hoped to learn the exact 
period in the year rabbits are free of ticks and conse- 
quently free of tularemia. We learned this and more. 
We noted unsuspected behavior patterns of the adult 
continental rabbit tick (//aemaphysalis leporis-palustris), 
seasonal fluctuations of the common eastern rabbit flea 
(Cediopsylla simplex), and additional facts concerning 
these and other ectoparasites. Herein is the report of 
our observations and of the collections on which they 
were based, 
Acknowledgment is made to Drs. Harlow B. Mills, 
Herbert H. Ross, Thomas G. Scott, Ralph E. Yeatter, 
and Carl O. Mohr, Mrs. Leonora K. Gloyd, Mrs. Diana 
R. Braverman,. and James S. Ayars, all of the Illinois 
Natural [listory Survey, for advice concerning inter- 
* Associate Taxonomist, Illinois Natural History Survey. 
T At time of study, Game Biologist, Illinois Department 
of Conservation. 
tThe Illinois Department of Conservation, the United 
States Fish and Wildlife Service, and the Illinois Natural His- 
tory Survey, co-operating. 
Lewis J. Stannard, Jr.,* and Lysle R. Pietsch} 
pretations and presentation of the data. Identification 
of some of the fleas was made or confirmed by G. P. 
Holland of Ottawa, Ontario. The photographs were taken 
by William IE. Clark of the Illinois Natural History 
Survey. We are indebted to Glenn I]aas, who has made 
a similar study in Wisconsin, for suggestions and con- 
structive criticisms. 
SCOPE OF STUDY 
Field work was conducted near Amboy, Lee County, 
on farm lands and idle fields, many of them similar to 
the field shown in fig. 1. Lee County is typical of most 
of northern Illinois. Here rabbits from two areas, each 
of about ] square mile, were examined. One area con- 
sistently had a much higher average per-acre population 
of cottontails than the other. The area with the greater 
number of rabbits yielded a greater number of ectopara- 
sites. In this report, data from the two areas are combined. 
Most of the rabbits examined were trapped alive, 
examined alive, and released. The ectoparasites were 
removed in the field, often as late as several hours 
after the rabbits were captured. Undoubtedly some 
ectoparasites were missed, such as those deep in the 
ears, but probably a large majority of the ticks and fleas 
were taken. Presumably not enough were overlooked to 
alter our conclusions appreciably. Nevertheless, the 
reported percentages of rabbits infested by each species 
of ectoparasite and the average numbers of ectoparasites 
per rabbit should be regarded as minima. 
The junior author collected over 10,000 ectopara- 
sites from more than 700 rabbits in the period beginning 
May, 1952, and ending November, 1954. Collecting varied 
in intensity according to the time that could be given 
to the study. The senior author sorted, identified, and 
counted the ectoparasites. 
Occasionally a rabbit was caught several times- 
within a season. For example, a rabbit designated as 
Peter II was caught nine times in July and August, 
1952, and each time all the ectoparasites found on it 
were removed and preserved. Other rabbits, No. 57 and 
No. 307, were caught five times each; several were 
caught four times; and as many as 30 were caught two 
or three times within a 2-month period. 
Additional 
Illinois (Jackson and Union counties) was gathered by 
Dr. Willard D. Klimstra of Southern Illinois University 
material from rabbits from southern 
