8 A NOTICE OF THE 



destructor, which probably restrains the increase of the first. It 

 deposits its eggs in the bodies of the larvae of the Hessian Fly, 

 and the young, when they escape from the egg, feed upon the 

 larva till it dies. 



During the year 1849, Miss Morris, of Germantown, dis- 

 covered that the Tomicus liminaris of Mr. Say, is a destroyer 

 of the peach-tree. It bores through the bark and feeds upon the 

 living portion. She has stated also that the Baris tripunctatus, 

 of Mr. Say, is one of the destroyers of the potato, in the stem 

 of which its larvae undergo their metamorphoses. And Mr. S. S. 

 Haldeman ascertained that the Hylesinus aculeatus, of Say, 

 feeds upon the inner bark of the white ash, Fraxinus acuminata. 



There was a time when a loathsome disease, which Van Hel- 

 mont tells us he contracted by shaking the gloved hand of a lady 

 friend, was treated by bleeding, purging, and sweating. Since 

 his days, investigations have demonstrated that this malady de- 

 pends upon the presence of an acarus the itch-insect and is to 

 be cured only by destroying the animal. There are several af- 

 fections attributed to the acarus tribe ; the ulcers caused by the 

 chigoe or jigger (Pulex penetrans), an insect which is prone 

 to burrow in human flesh, are familiarly spoken of by all who 

 have visited the tropics. The harvest-bug (Leptus autumnalis) 

 buries itself in the legs of laborers in the harvest-field, pro- 

 ducing intolerable itching and pain. In cases of plica polonica, 

 an affection of the scalp, we are told that millions of lice appear 

 on the third day of the disease. Numerous affections have been 

 traced to the larvae of flies deposited in the tissues of mammals ; 

 a disease familiarly known as the bots, which occurs in horses, 

 sheep, and in man, has this origin. Worms of several kinds are 

 known to thrive in the human body, and to produce disease. In- 

 deed, the affections known to be caused by insects, spiders, worms, 

 &c., are so numerous, that Easpail has ventured to construct a 

 system of medicine based upon the animate origin of diseases. 

 In his work, may be found a history of many affections, caused 

 by the presence of minute parasitic insects.* 



Though many evils arise from insects, they are also the sources 

 of much that is good. The product of the silk-worm, the wax 



* Histoire Naturelle de la Sant6 et de la Maladie chez lea veg6taux et 

 chez les animaux en general, et en particulier chez Phomme. Par F. V. 

 Raspail. Paris, 1843. 



