162 ORDER HOMOPTERA. 



moving the plant-lice are by no means inconsiderable. He might, indeed, advantageously 

 stock bis house-plants with the coccine/ia, lor the purpose of keeping them clear of lice. 



I have already adverted to the lacewing : in its larva state, it is probably one of the 

 most sanguinary enemies of plant-lice. Where these abound, the eggs of the lacewing may 

 be Been each supported on the end of a slender thread.The larva or grub is provided with 

 a large pair of curved pointed hollow jaws, with which he seizes the aphis, and sucks all 

 the fluid contents of its body, leaving nothing but a collapsed skin. 



Mr. Kirbv states the tact, which is also now well known to many, that a 11 y belonging 

 to the Genus Syrphis is equally effective in exterminating the aphis; their larva? or 

 maggots having completely exterminated a colony which had a week before infested his 

 currant-bushes. 



Coccidae. 



The bark-lice form a third division of singular insects, from which, judging from the 

 appearance of a few individuals among them, we should never expect serious injury to 

 trees or plants. They vary in form : sometimes they are kidney-shaped scabs, beneath 

 which, at some period or other, may be found a brood of minute lice : others are oval, 

 quite large and globular, of a dark gray color, and are fixed to the surface of the bark, or 

 have lost the power of locomotion ; these are females. 



As an illustration of the character of the Coccida, I may state that the matter of the 

 cochineal of commerce, brought to us from Mexico, is an insect of this family. 



These insects are usually known under the name of bark-lice, of which the kind that 

 inhabits the branches of the appletree is probably the most common. They differ in struc- 

 ture from the aphides, their feet consisting of a single joint terminating in a claw. The 

 male is quite small in comparison with the female, and, like that of the aphis, is provided 

 with wing>;, which are two in number, and lie flat upon the body as in the Genus Thkips. 

 The female, after she has become fixed to the limb or bark of the tree, having lost the 

 I>ower of locomotion, brings forth beneath her a brood of young, which, when able to run 

 about, escape from the dry skin of the parent, and fix themselves by their beaks to the 

 bark, where they grow and become mature upon the sap of the tree. 



A maple at my door in Hudson-street, Albany, is infested with thousands of individuals 

 of a species of Coccus, about the twentieth of an inch in length, and covered with the 

 woolly matter peculiar to the family, which imparts to the limbs a snowy appearance. On 

 the first of September, the back of the leaf supports some twenty individual females of a 

 green color, beneath which are the young. 



Trees suffer from the minute punctures of bark-lice ; the apple-tree particularly, which 

 is infested with a kind that resembles a dry scale, having the color of the cuticle of the 

 bark on which it rests. The remedies for these depredators are the same as have been re 



