m3 15 Nat. Hist. Surv. 
LlGi 
Mai Illinois Natural History Survey THE LIBRARY OF TI 
ADP fF 1Orh 
Section of Faunistic Surveys & Insect Identification oT Se Ss ee 
UNIV RS . tNtr 
Urbana, Illinois ERSITY OF ILLIN( 
March 17, 1955 Identification Notes 3 


Ticks of Importance in Illinois 
Lewis J. Stannard, Jr. 
Ten species of ticks are known to occur in Illinois. Another half dozen 
more species eventually may be found, either occasionally from shipments of 
livestock or from resident species of mammals and birds. Of the common I1lli- 
nois ticks, two are dangerous as the proven vectors of diseases often fatal 
to man, and several more are suspected to be vectors of these and other dis- 
Casé€Se 
Ticks belong to the large group that includes spiders, scorpions, and 
mites. This group of animals, in the adult stage, always possesses four pairs 
of legs. By contrast insects, which are distant relatives of ticks, have only 
three pairs of legs when fully grown, Unlike spiders and scorpions, ticks 
have no external division between the abdomen and the anterior part of the 
body that bears the legs. From most mites, ticks differ in being larger and 
in being covered by a hard, tough epidermis. Usually they are so tough that 
it is impossible to crush them between one's fingers. | 
In their development from egg to adult, ticks pass through several dis- 
tinct stages. From the egg, there issues a larva which has only three pairs 
of legs. This larva feeds on blood, grows, and molts into the nymph, which, 
like the adult, has four pairs of legs. Nymphs feed and transform into adults, 
in which stage the genital opening appears, usually situated between the first 
two pairs of coxae. Ticks of the family Argasidae lay only a few eggs at a 
time and have two nymphal stages. Ticks of the family Ixodidae lay their eggs 
in large masses and have only one nymphal stage. 
Structures used in the following key and discussion are: 
Capitulum: the movable front part of the body on which 
is situated the mouth parts. The base of the 
capitulum, fig. 1, BG, lies behind the mouth 
parts and its shape is of use for determining 
species. 
Palpi: the paired, outer, segmented appendages of 
the mouth parts. Seen from above only segments 
II and III are visible, fig. 1. Segments I 
and IV are small and lie underneath. 
Byes: when present, a pair of eyes, each composed 
of a single lens, is borne on the sides of the 
tick body, fig, 1, In preserved specimens the 
eyes sometimes become so transparent they are 
difficult to detect, 
RIATIINA 
NATURAL 
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wae beware 
