626 HEMIPTEBA. 



which the wings are of a uniform ; in the second, of a varied 

 texture. (To the section Homoptera, Latreille gives the name 

 Hemiptera, while Leach calls it Omoptera.) Westwood divides 

 the Homoptera, which he considers a distinct order, into three 

 sections, viz : Trimera, (.Gr. three parts,) Dimera, (two parts,) 

 Monomera, (one part or division,) these terms having reference 

 to the divisions of the tarsi; and the Heteroptera into two sec- 

 tions, Hydrocorisa, (residents of water,) and Aurocorisa, (resi- 

 dents of air.) 



Of the Homopterous division, having the four wings all of a 

 firm membraneous texture, are the BARK-LICE, or SCALE-INSECTS, 

 Coccida, (typ. gen. Coccus.) (Plate XV. fig. 14.) Of these 

 there are several species, found on the leaves and bark of dif- 

 ferent plants. The Coccus cacti (of the cactus,) is, on account 

 of its beautiful crimson color, used as a coloring-matter. It is a 

 native of Mexico, and feeds upon a particular kind of Cactus, 

 called Indian-fig, and extensively cultivated for the express pur- 

 pose of rearing it. The annual amount of Cochineal exported 

 to Europe is, according to Humboldt, eight hundred thousand 

 pounds; and it requires about seventy thousand insects to make 

 a pound. Lac or Shell-lac, employed for making sealing-wax, 

 is the product of a species of Coccus. The Mealy-Bug, Coccus 

 adonidum, (of Adonises or flowers,) found in hot-houses, is red- 

 dish, but covered with a white, powder-like substance. The 

 Coccida belong to Westwood's Monomera. 



The PLANT-LICE, or Vine-fretters, Aphida, (leading genus 

 Aphis,) infest the roots of vegetables, (often doing them great 

 injury,) and also the leaves of most plants, such as roses, asters, 

 apples, pears, peaches, cabbages, &c., each plant having its 

 own peculiar species. Their bodies are soft, of an oval form 

 and have upon the abdomen two tufts or pores. The females 

 are usually wingless, but not always. The upper wings corres- 

 ponding to the wing-covers in the Hemiptera Proper, are the 

 larger and used for flight or as aids in leaping. To the prolific 

 powers of the Plant-lice reference has already been made. A 

 young leaf that curls, or that has an unhealthy appearance, is 

 probably infested with these lice. Fumes of tobacco, turpentine 

 or sulphur, are a remedy against them, and also against the 

 Mealy -Bugs. The Aphida belong to the Dimera. 



The WOOL-FLY, or the Apple-tree-blight, Eriosoma, (Gr. erion, 

 wool ; soma, body.) is an insect of a woolly appearance ; without 

 wings, but wafted from tree to tree by its cotton envelope. Its 

 microscopic eggs, covered with the same soft, downy.substance 

 as the body, are found in the crotches and chinks of trees, where 



