89 



7. The same species appears to insinuate itself, in its incipient 

 state, upon the human body, but is not known to assume the tick form 

 there. They adhere most tenaciously to the skin, and are believed 

 to introduce themselves below it. They are very harassing, and even 

 create soreness and inflammation. They generally affect persons 

 who have been passing through woods, but are not known to be ever 

 seen or found on trees or plants. 



8. Many thousand head of cattle are annually carried off by the 

 carapatoes, and frequently a scarcity is thus caused. 



This is all the information I have been able to collect on the sub- 

 ject, and I am not aware that any other account is given by travellers 

 in South America. 



From the above particulars it would appear that the little acaroid 

 insect now before the Society is only the young of a much larger spe- 

 cies of tick. What this species may be is perhaps not to be deter- 

 mined in the absence of full-grown specimens; but from the structure 

 of its oral apparatus, it is plainly to be referred to the genus Ixodes 

 of Latreille ; with respect to which it is stated by Cuvier, that " they 

 are found in thick woods, abounding in brush-wood, briars, &c, at- 

 taching themselves to low plants by the two fore legs, extending the 

 other feet. They fasten upon dogs, cows, horses and other quadru- 

 peds, and even upon the tortoise, burying their suckers so completely 

 in their flesh, that they can hardly be detached by force, and by tear- 

 ing away the portion of skin to which they are fastened. They depo- 

 sit a prodigious number of eggs. Their multiplication upon the ox 

 and horse is sometimes so great, that these animals perish from ex- 

 haustion. The tarsi are terminated by two ungues, inserted upon a 

 plate, or are united at the base upon a common peduncle," &c. 



In these particulars, it will be observed how closely the above de- 

 scription coincides with the statement I have above given on the sub- 

 ject of these observations. But no mention is made of any difference 

 between the immature and the full-grown insect ; and consequently, 

 perhaps the present account may not be unimportant to those who are 

 engaged in the study of the still confused but highly interesting para- 

 sitic Acaroidei. 



Figs. 1 and 2 (Plate ix.) represent the dorsal and abdominal as- 

 pects of the insect, which, in its present state, has only six legs, in 

 which it agrees with the group Microptheria of Latreille, which thus 

 differ from other Acaroidei. In this respect, however, it is not pecu- 

 liar, some species of Hydrachna, in the young state, also possessing 

 but six legs. 



h2 



