ARTICULATA. 123 
According to Dujardin, the supposed genus /Zypopus of Dugeés, which 
was placed in this family, is the immature condition of Gamasus. 
Fam. 4. Ivodide. The genus Lzodes (pl. 77, jigs. 67, 71) includes the 
parasitic animals known as ticks. The eyes are wanting, and the body has 
a tough integument; their form is oval, and flat and scale-like when found 
among grass and bushes; but when they have affixed themselves to the 
animals which they infest, they become greatly distended, so that an indi- 
vidual a tenth of an inch long may acquire a length of one third of an inch 
or more by distension, when it resembles a small bean. Being very slow in 
their movements, they must wait long before they are afforded an oppor- 
tunity to affix themselves where they can suck blood, so that the distensi- 
bility of the body and the division of the stomach into various large branches, 
enable them to make amends for a long fast, as in the case of the leech. 
The position of the animal in its parasitic state is maintained by the rostrum, 
which is composed of three hard corneous pieces, two above (the mandibles), 
their extremity armed with a movable piece margined with teeth, and one 
below, which is the labinm. This is obtusely rounded at the end, concave 
above, and armed upon its lower surface with transverse rows of serriform 
teeth, with their points directed backwards, and recalling the somewhat 
similar structure in the Acanthocephala (p. 47), and designed for a similar 
use. In a state of repose, the external margins of the mandibles are clasped 
by the palpi, the hairs of which cover the labinm beneath. The explana- 
tion of the parts of the mouth given here, is that of Dugés. 
The feet in this family are robust, and have six articulations, and when 
the animals are among plants, and ready to attack their prey, they suspend 
themselves by two of their feet, extending the others to affix themselves to 
any passing animal. Say took Lodes annulatus from a deer, and JL. orbicu- 
latus from a squirrel. They torment and even kill cattle when they are 
abundant; dogs suffer much from them, and in the West Indies they must 
be removed from horses and asses once a week. They also attack birds, 
tortoises, lizards, and serpents. They seem to be common in various parts 
of the world, but their distribution is local, as they are unknown in certain 
localities and common to others not very distant from the former. Say has 
described nine species inhabiting the United States, including the small and 
troublesome seed-tick, which renders an excursion so disagreeable in some 
parts of the western states. The species attack man, and cause a trouble- 
some sore, the effects of which may continue in an occasional itching, 
for a period of several years. 
Fam. 5. Gamaside. Palpi slender, short, fies, and incurved, body 
depressed, eyes wanting; parasitic upon beac, birds, reptiles, and insects. 
In Gamasus the body j is oval, tough, and scutiform abicnve; the mandibles 
cheliform, and the first pair of feet are slender, and the second thick. They 
are often seen running upon the ground, and when they are upon the 
_ animals which they infest, they run about from place to place, differing from 
Ixodes in this respect, and in not gorging themselves to such an extent. 
Gamasus coleopterorum has the back covered with two pale brown plates 
divided and surrounded by a light space. It is found in Europe and the 
327 
