68 



DIRECT INJURIES CAUSED BY INSECTS. 



semble the common lice, except in being whiter ; but medical 

 men, who were not at the same time entomologists, might 

 easily mistake an Acarus for a PediculusJ 



Dr. Willan, in one case of Prurigo senilis, observed a 

 number of small insects on the patient's skin and linen. 

 They were quick in their motion, and so minute that it 

 required some attention to discover them. He took them at 

 first for small Pediculi ; but under a lens they appeared to 

 him rather to be a nondescript species of Pulex ^ ; yet the 

 figure he gives has not the slightest likeness to the latter 

 genus, while it bears a striking resemblance to the former. 

 It is not clear whether his draughtsman meant to represent 

 the insect with six or with eight legs : if it had only six, it was 

 probably a Pediculus ; but if it had eight, it would form a 

 new genus between the Acarina and the hexapod Aptera. 

 Dr. Bateman, in reply to some queries put to him, at my 

 request, by our common and lamented friend Dr. Keeve, 

 relates that he understood from Dr. Willan, in conversation, 

 that the insect in question jumped in its motion. This 

 circumstance he regards as conclusive against its being a 

 Pediculus; but such a consequence does not necessarily 

 follow, since it not seldom happens that insects of the same 

 tribe or genus either have or have not this faculty ; for in- 

 stance, compare Scirtes with Cyphon, small beetles, and 

 Acarus Scahiei with other Acari.^ 



Dr. Willan has quoted with approbation two cases from 

 Amatus Lusitanus, which he seems to think correctly de- 

 scribed as Phthiriasis. In one of them, however, which 

 terminated fatally, the circumstances seem rather hyper- 

 bolically stated — I mean, where it is said that two black 

 servants had no other employment than carrying baskets full 

 of these insects to the sea ! ! Perhaps you will think I draw 

 largely upon your credulity if I call upon you to believe this ; 

 I shall therefore leave you to act as you please. — Thus 



1 From the terms employed by Aristotle and Dr. Mead in their account of 

 these cases, it appears that the animal they meant could not be maggots, but 

 something bearing a more general resemblance to lice. 

 On Cutaneous Diseases, 87, 88. ; and t. 7. /. 4. 



3 Latreille at first considered this as belonging to a distinct genus from the 

 common mite (Acarus domesticus), which he named Sarcoptes but upon its 

 being discovered that it also has mandibles, he suppressed it (A^. Diet. d'Hist. 

 Nat. xxi. 221.) ; hut it has been since resumed by M. Duges and other authors. 



