f e = 
Aa 
f : lier : 
{ L . 
y -_-- — eee ' 
t-| ae) -—-—-— 
/ | eeu 
f ees (= pee l| j 
cas is Ff t - ‘ 
Cs; | i = 1 feral 
pee a Me) 
[- = f Py proces | i 
> mae’ = 1 
eat ae ail Lal | ~ 
5 Soe! J 
T {| —+4—-—~ 
j i JS | 
5 a = acer (a j 
T (Ni @ fH 
ae 7 Seat cola 
\ | Png lie he 
\ |e, e e \ L 
fs | DE 
Ie Nell ih ne hp 
Sp 2) l | f 
| es 
f Le +-.--4 et 
re ae ieee 
xe fer ee 
PY Oo eis 
gy C= amias 
ee ti ee 
Fig. 13.—Odontopsyllus multispinosus distribution in IIli- 
nois, based on []linois Natural History Survey records. 
No chiggers were taken on rabbits in Lee County; 
possibly they were overlooked. 
CONCLUSIONS 
Ectoparasites of cottontail rabbits, particularly the 
continental rabbit tick, Haemaphysalis leporis-palustris, 
are significant components of the wildlife of Illinois, 
and, as such, have had a decided effect on man’s activ- 
ities inrecent years. Because of newly gained knowledge 
of the seasonal behavior of the continental rabbit tick 
on cottontails, the Illinois hunting laws were changed 
in 1955. Ecke (1948) and Yeatter & Thompson (1952) 
had shown conclusively, as we found during our studies 
in Lee County, 1952-1954, that those ticks which are 
vectors of tularemia are absent from rabbits in late fall 
and most of the winter in northern and central Illinois. 
Postponement of the hunting season until late fall to 
avoid the tick season and the consequent hazards of 
tularemia was the logical course of action which fol- 
lowed the reports of such information. 
In our limited survey of ectoparasites of cotton- 
tails in Lee County, we observed the following funda- 
mental features of the intricate relationships between 
ectoparasite and host: (1) Adults of the continental 
rabbit tick rarely feed on rabbits in fall. (2) Ticks and 
fleas reach their greatest abundance at different sea- 
sons of the year, as if each of the two groups gains an 
16 
advantage by a division of time on the host. (3) The 
eastern rabbit flea, Cediopsylla simplex, occupies the 
head region of its host, whereas the giant eastern rabbit 
flea, Odontopsyllus multispinosus, occupies the back of 
its host, as if each of the species gains an advantage 
by eliminating competition for space. (4) The variable 
wood tick, Dermacentor variabilis, as an adult, is ab- 
sent from rabbits when, in the same geographical region, 
it heavily infests other mammals such as opossums 
and raccoons. (5) Only two species of ectoparasites, 
the continental rabbit tick and the common eastern rab- 
bit flea, are consistently numerous at certain seasons, 
whereas other ectoparasites, such as Odontopsyllus 
multispinosus and Ixodes dentatus, which are supposedly 
equally restricted and equally adjusted to rabbit hosts, 
remain relatively rare most of the time. 
Asis indicated bythe aforementioned observations, 
the behavior patterns of ectoparasites of rabbits are 
extremely complicated. What factors, it may be asked, 
could catise one of the two ticks and one of the two 
fleas restricted to rabbits to be common and the others 
to be rare? Or what factors could cause the adult of the 
variable wood tick to infest almost every mammal the 
size of a rabbit or larger, but not be found on rabbits? 
Why do the ticks that are primarily ectoparasites of 
rabbits feed in the adult stage only on rabbits, yet in 
the immature stages find birds as acceptable as rabbits? 
Surveys such as ours cannot provide answers to 
many questions; rather, they provide a few facts that 
suggest further questions. Thorough and detailed in- 
vestigations of the life history and environment of each 
ectoparasite and the habits and environment of the host 
need to be undertaken and correlated before much can 
be deduced as to the origins and the conditions for 
optimal survival of ectoparasites. 
Ectoparasites of cottontail rabbits, because they 
are easy to obtain and because preliminary studies on 
them have been made here and elsewhere, are worth- 
while subjects for future research. 
SUMMARY 
Seven facultative or obligate ectoparasites were 
taken from about 700 cottontail rabbits collected in Lee 
County, northern Illinois, in a period beginning in May, 
1952, and ending in November, 1954. 
The continental rabbit tick, Haemaphysalis leporis- 
palustris, the principal vector of tularemia, was the 
most common tick found. Very few specimens were col- 
lected from rabbits from late autumn to late winter. 
Adults of this tick were collected from rabbits 
from late winter to midsummer. They reached their great- 
est abundance on cottontails in spring. The adults rare- 
ly infested rabbits in autumn or early winter; they were 
