ARTHROPODA. 107 



Order III. HEMIPTEEA. 

 RYXGOTA. SIPHONATA. DERMAPTERA. 



Four wings, more or less membranous. Mouth produced into 

 an acute suctorial proboscis (mandibulate in Mallophaga). Larva 

 with no trace of wings. Pupa active, semicoinplete. 



The proboscis is formed by modifications of the labium, man- 

 dibles, and maxillae, and, except in Thripidag, there are no palpi. 

 The upper wings in the more normal forms are merely coverings 

 (tegrnina) for the lower, but they always differ in size and texture ; 

 in some cases they are covered by the scutellum. The females 

 have frequently an ovipositor, by which galls are often produced. 

 Ocelli are very commonly present. In some Nepidie there are 

 caudal setae connected with anal spiracles and subservient to 

 respiration. 



The greater part of the Hemiptera are vegetable feeders, suck- 

 ing the juices of plants. The Aphides, of which there are about 

 350 British species, are the most obnoxious ; Coccidae are also 

 very injurious. In the West Indies, Delphax saccharivora is very 

 destructive to the sugar-cane. Coccus cacti, when dried, is the 

 cochineal of commerce ; a pound weight contains 70,000 insects. 

 Coccus lacca yields the prepared substance called shell-lac. Dor- 

 thesia secretes from the end of the abdomen long snow-white 

 flocculent masses of a waxy character. Ancyra, Plata, Lystra, and 

 others are also wax-producers ; some are so completely enveloped 

 in this secretion as to be unrecognizable. The "Pela," or Chinese 

 wax, is prepared from this substance. Manna is a vegetable secre- 

 tion caused by Coccus manniferits. 



The eggs of Corixa mercenaria form a food extensively used by 

 the Mexicans. They are collected in freshwater lakes, or are 

 washed on shore. A white limestone rock is forming at the pre- 

 sent day in the lakes of Texcono and Chalco from their remains. 



There is a tendency to degradation in this order, as shown by 

 the frequent absence of wings, an obsolete mouth, a tarsus re- 

 duced to one joint, &c. In the Coccidae many of the females 

 become more and more inert as they approach the imago state, 

 and the young are sometimes hatched beneath the dead body of 

 the parent. 



Westwood places Hemiptera between Diptera and Lepidoptera ; 

 Glaus (as Ehynchota) between Neuroptera and Diptera. 



Besides plant-lice (Aphidas) and scale-insects (Coccidae), this 

 order contains the lantern-fly (Fulgora laternaria}, frog-hopper 



