ARTICULATA. 123 



According to Dujardin, the supposed genus Hypopiis of Duges, which 

 was placed in this family, is the immature condition ofGamasus. 



Fam. 4. Ixodida. The genus Ixodes {2>l. 77, Jigs. 67, 71) includes the 

 jjarasitic 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 l3ushes ; but when they liave 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 labium. This is obtusely rounded at the end, concave 

 above, and armed upon its lower surface with transverse rows of serrifui'm 

 teeth, with their points directed backwards, and recalling the somewhat 

 similar structure in the Acanthocejjhcda (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 labium beneath. The explana- 

 tion of the parts of the mouth given here, is that of Duges. 



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 

 an}' passing animal. Say took Ixodes annulatus from a deer, and /. orlicu- 

 latus from a squirrel. They torment and even kill cattle when they ^re 

 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. Gamasidw. Palpi slender, short, free, and incurved, body 

 depressed, eyes wanting ; parasitic upon beasts, birds, reptiles, and insects. 

 In Gamasus the body is oval, tough, and scutiform above, 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, diflering from 

 Ixodes in this respect, and in not gorging themselves to such an extent. 

 Gamasus coleojpteroruin has the back covered with two pale brown plates 

 divided and surrounded by a light space. It is found in Europe and the 



A 327 



