CHAP. VI. INJURIOUS INSECTS. 207 



maggots ill general, is a question involved in much 

 doubt ; but all agree in stating that it was produced by 

 insects. Considering the conflicting accounts that have 

 been given, it seems highly probable that more than 

 one disease has been confounded under this general 

 name, each produced by a different insect. Dr. Willan, 

 in a case of prurigo senilis, observed a number of small 

 insects on the patient's skin and linen, which were quick 

 in their motions, and very minute. He took them, at 

 first, for small lice ; but Mr. Kirby rather suspects they 

 belonged to a new genus, allied to the Acarus. 



(222.) The Acaridce, or harvest bugs, indeed, con- 

 tain a host of enemies to our race ; they cause ex- 

 cruciating pain, by digging into the cuticle of the skin, 

 and, in some instances, establishing themselves beneath 

 it. Dr. Adams conjectures they may be the cause of 

 certain cases of ophthalmia, a disease remarkably pre- 

 valent in Egypt, and from which our troops suffered 

 most severely. We are decidedly of the same opinion; 

 notwithstanding the popular notion, then prevalent, that 

 this disease, which generally terminated in total blind- 

 ness, originated from the glare of the hot sands of the 

 desert. Our medical officers soon found that the Egyp- 

 tian ophthalmia was infectious, and that it spread rapidly 

 among those regiments of which part of the men only 

 had been to Egypt, and the rest had remained in Sicily: 

 a clear proof that the disease could not have originated 

 from the above cause. Sir J. Banks attests that, several 

 seamen of the Endeavour brig being tortured with a 

 severe itching round the eyelids, an Otaheitan woman 

 cured one of them by extracting an abundance of very 

 minute lice. We can, from personal experience, bear 

 testimony to the excruciating pain caused by more than 

 one species of Acarus, called by the Brazilians Cara- 

 pato. They are found, in the dry season, among the 

 parched-up herbage, and seem to be gregarious ; for we 

 have sometimes found our garments, on going through 

 a break of the forest, suddenly covered with them, as 

 if they congregated together, ready to catch hold of 



