that the metamorphosis is very imperfect, and 

 seems to consist in a series of consecutive 

 changes of skin, end gradual increase in size, 

 such as might be expected in an animal ih its 

 progress to maturity, rather than to form a Tiieta- 

 morphosis, properly so called. In allffiages 

 they are active, and possess the power of taking 

 food. 



It is of importance, in a practical point of view, 

 to be acquainted with the mai-ks by which tliese 

 troublesome and disagreeable parasites are dis- 

 tinguished, because different methods of des- 

 troying them require to be adopted according to 

 their different habits and places of residence. 

 The whole tribe is divided into two sections ; the 

 one containing such species as are provided with 

 a tubular sucker, the other, the kinds having the 

 mouth provided witli two homy mandibles or 

 jaws. These differences in the structure of the 

 mouth must obviously exercise a great influence 

 on their habits and general modes of procedure. 

 The first we shall notice, which is one of the 

 most common and troublesome, belongs to the 

 last-mentioned division; it is the Trichodcctes 

 scalaris. The genus Trichodectes is known by 

 having the autennffi three-jointed ; the tarsi with 

 one claw ; the head horizontal and sajjle-like, 

 with the mouth beneath ; mandibles stj-ong, tri- 

 dentate at the apex; the eyes very inconspicuous, 

 and at all times invisible. All the species live 

 upon quadrupeds, their food consisting of hair, 

 wool, and exfoliated particles of the epidermis. 

 Their jaws act horizontally, and cut off the hair 

 close by the roots, exactly as if it had been done 

 with a pair of scissors. 



T. scalaris, Peditmlus, 

 hovis, Linn. Louse of 

 THE Ox, is about half a line 

 in length, the head and tho- 

 rax of a bright rust-yellow, 

 the former with two dusky 

 spots in front, and of an ab- 

 cordate shape ; eyes prom- ^ 

 iuent ; antennae pale yel- j// 

 low, the third joint longest ^ 

 and spindle-shaped ; abdo- 

 men oblong, pale, tawny, 

 finely pubescent, the first 

 six segments with a trans- 

 verse rust-red or dusky 

 band on the upper half, and 

 a large longitudinal spot of 

 the same color on each side ; 

 the hinder extremity with a large similarly col- 

 ored spot ; legs pale ; tlie claws nearly straight. 

 (Fig. 1.) 



This species is very common on cattle, and 

 for the most part is found about the roots of the 

 hair on the mane. 



T. eqiii, Pediculus equi, 

 Linn. Louse of the 

 Horse. — Nearly one half 

 larger than the preceding, 

 but in other respects bear- 

 ing a close resemblance to 

 it. The head and thorax 

 are of a bright chestnut 

 color ; the head somewhat 

 square, with the angles 

 rounded, and much wider 

 than the thorax, having an 

 angular dusky line on each 

 side posteriorly; antennjE 

 pale, thick, the last joint 

 longest, and somewhat club 

 jshaped ; abdomen obcon- 

 (1038) 



Fig. 2. 



A- 



^^'^ 



ical, colored nearly as in T. scalaris ; legs pale, 

 thick and sti-ong, the tibiaj abruptly clavate ; the 

 tarsi short. (Fig. 2.) 



Common on the horse and ass, mnltiplving to 

 a great extent when these animals are afflicted 

 with certain kinds of diseases. It is said to be 

 most plentiful when the animals are fresh from 

 pasture. Several other species belonging to this 

 genus are found on different animals. One oc- 

 curs on the sheep, [T. sph(eroceplialus.) another 

 ( T. luniitcornis) on the fallow-deer, and a third 

 ( T. stmihs) on the red-deer ; but thev never ap- 

 pear to increase on these animals to an injuriouB 

 extent. 



Heematopinus cm- Fig. 3. 



rysteryius. Louse of 

 THE O.x. — In this gen- 

 us the mouth is formed 

 for sucking, there be- 

 ing a short tube pro- | 

 jecting from the mouth ;>; 

 the antenna are five- 

 jointed ; the thorax dis- 

 tinctly separated from 

 the abdomen, and much 

 narrower, shorter and 

 broader than the head ; 

 abdomen large, de- 

 pressed, commonly 

 oval, consisting of eight or nine .segments ; legs 

 formed for chmbing, very thick and strong; 

 claws single and incurved. Perhaps the most 

 plentiful of all the species which infest cattle is 

 that named above. The head, which is of a 

 chestnut color, is somewhat triangular, rounded 

 behind ; the thorax dull chestnut, nearly square, 

 with a spiracle and an impressed line on each 

 side ; abdomen greyish-white, or ochrey, smooth 

 and shining, with four longitudinal rows of 

 dusky, horny excrescences, the last segment 

 with two black, curved marks ; legs chestnut, 

 the extremity of the claws black. Length from 

 1 to 1^ lines. (Fig. 3.) 



It is this species, for the most part, that proves 

 so troublesome to stalled oxen. It frequents 

 chiefly the mane and shoulders. Being a suc- 

 torial insect, it cannot directly strip off the hair, 

 but, by abstracting the juices by which the bulb 

 or root of the hair is nourished, it makes it more 

 liable to fall ofl', and the irritation its punctures 

 occasion causes the animals to nib themselves 

 till the skin is quite bare. Mr. Denny remarks 

 that the yoHng are much more agile than the 

 mature insect, and difler in nothing except a 

 want of proportion, the limbs being much thicker 

 as compared with the bulk of the body than 

 when adult. Another species, somewhat similar 

 in appearance, (//. ■vituli,) occurs in the calf, 

 but it does not appear to be common. 



Hamatopimis suis. Fig. 4. 



Pediculus suis, Linn. 

 Louse OF Swine. — Head 

 and thorax dusky rust- 

 color, the fomur some- 

 what pear-shaped, with 

 an angular black line at 

 the apex, and one on each 

 side before the eyes ; 

 hinder angles of the tho- ; 

 rax acute, each side with 

 a distinct spiracle ; abdo 

 men large, flat and oval ; 

 of a membranaceous con- 

 sistency, bluish of yel- 

 lowish ash color, sometimes nearly white ; the 

 second and five following segments with a black. 



