868 



INSECTA. 



however, has recently described one species, 

 P. GigttS,* which is two lines in length. 



Order XII. APTERA. 



Wings none ; body ovate, flattened ; head 

 distinct from the thoracic segments, which are 

 narrower than those of the abdomen ; mouth 

 either haustellated or mandibulated ; metamor- 

 phosis incomplete. 



This order, which is formed of the Pediculi 

 of Linnaeus, and is based upon the entire 

 absence of the wings and an incomplete meta- 

 morphosis, affords a striking proof that we 

 ought not in our arrangements to place too 

 much dependance upon the presence or ab- 

 sence of any one particular set of organs, or 

 kind of metamorphosis; else, as well remarked 

 by Burmeister, we ought to include among the 

 Aptera the female Blatta and the common 

 Cimex, insects which evidently belong to 

 different orders. But it may be further ob- 

 served that dissimilarity in the structure of one 

 particular kind of organs is not alone sufficient 

 to authorise the separation of genera which in 

 other respects are closely united ; otherwise 

 the Ninnidte (fig. 351) ought to be separated 



Fig. 351. 



, the Bird-louse. 



from the Pedtculidtf, although resembling them 

 in every thing excepting the structure of the 

 mouth, the very part of the animal upon which 

 the two great divisions of insects in the present 

 arrangement is founded. 



Order XIII. HEMIPTERA. 



Wings four, anterior ones partly leathery, 

 partly membranaceous, decussating each other 

 at the apex; posterior wings entirely mem- 

 branaceous ; pro-thorax and scutellum very 

 large; mouth rostriform, composed of elon- 



F ig. 352. 



gated seta:; ocelli three; metamorphosis in- 

 complete. 



This order is divided into two sections, Ter- 

 rcstria and Aijuntica. 



The larva and pupa are active, and most 

 species subsist upon the juices of other ani- 

 mals. The Terrafria are distinguished chiefly 

 by the length of the antenna.', which exceeds 

 that of the head, and by their three-jointed 

 tarsi. The Aquatica have the antennae in 

 general shorter than the head (which in some 

 species (jig. 352) is sunk into the pro-thorax), 

 the eyes are large, the rostrum short, and the 

 tarsi with only two joints. 



Order XIV. HOMOPTERA. 



Wings four, anterior pair either entirely 

 coriaceous or membranaceous, not decussating 

 each other ; pro-thorax very short ; head large 

 and transverse ; antennae shorter than the head 

 in most genera; abdomen in some furnished 

 with a compound serrated ovipositor; meta- 

 morphosis incomplete. 



This order is considered by many authors as 

 only a section of the preceding. It is, how- 

 ever, composed of several distinct families. 

 The types of the order, the CicudiidtE (Jig. 

 353), tree-hoppers, in possessing a serrated 



Fig. 353. 



A'qjo cinrrea, the Water-scorpion (Samoucllc). 

 * Fauna Borcali-Amcricana, 1837, p. 318. 



Cicada heematodes (female). (Samouellc). 



ovipositor seem to approach to the Terebrantia, 

 while the Thripidte, which in the structure of 

 the mouth resemble mandibulated insects, have 

 recently been formed into a distinct order,* 

 and have been placed by Mr. Westwood before 

 the Neuroptera. Perhaps a closer examination 

 of the remaining families, Aphidte and Coccida, 

 the plant-lice, &c., might lead to a similar 

 removal. 



In the preceding remarks we have closely 

 adhered to the arrangement proposed by Mr. 

 Stephens, but it cannot be denied that much 

 remains to be done before the entomologist will 

 be able to form an arrangement so far natural 

 as to be free from serious objections. The 

 principal divisions of the last two orders, in 

 possessing ocelli, in the size of the thorax, the 

 connexion of the wings during flight (which 

 we shall hereafter show exists in some of the 

 Cercopiidte,) and in the serrated terebral ovi- 

 positor, seem to be more nearly connected 

 with the Hymenoptera than with the wingless 

 and less perfectly developed Aphaniptera and 

 Aptera. 



From the above remarks on the orders it will 



* Thysanoptera. Haliday, in Entom. Magazine, 

 vol. iii. & iv. 



