208 HABITS AND INSTINCTS OF ANIMALS. CHAP. VI. 



the first living object which passed that way. They 

 immediately begin to burrow with their snouts into the 

 skin, where they get so firm a hold, that it is frequently 

 necessary to use a sharp instrument to pick them out : 

 if this be done by taking hold of their body, much 

 danger is risked, for the head generally remains in the 

 skin; and this, if not extracted, causes intolerable pain, 

 and, finally, severe ulcers. The annexed cut ofAcarus va- 

 riegatus (fig. 63.) magnified, will give 

 a perfect idea of these detestable pests. 

 It is probable that the insect named 

 by Linnaeus Pediculus ricino'ides, on 

 the authority of Rolander, is one of 

 these, simply from this circumstance, 

 that, so far as our observations 

 have extended, there is no insect 

 known in South America, which "gets 

 into the feet of people who walk," 

 except the chegoe, common also in the West Indies. 

 The whole of the Acari, or harvest bugs, are emi- 

 nently parasitic; and, in all probability, the only tribe 

 of apterous insects, except the true Pediculus, or louse, 

 which preys upon man. The fact mentioned by Lin- 

 naeus, that a minute species, swallowed in water, pro- 

 duced a violent dysentery, is incontestable, and gives no 

 small sanction to the belief that many of the modifi- 

 cations of this disease have the same origin. To these 

 pests, also, many learned and intelligent writers have 

 traced the itch. There are, no doubt, several species 

 if we may use the expression of this disease, each, in 

 all probability, originating from a different cause ; but 

 that more than one of these are to be attributed to in- 

 sects has been sufficiently proved. Our ignorance, in 

 fact, on the connection between insect agency and bodily 

 disease, is so great, that the discussion would lead to 

 nothing satisfactory. We have long been of the same 

 opinion as was Linnaeus, that the plague originates 

 from the same cause. We were in Malta during the 

 whole time that island was afflicted with this terrible 



