Charles Brongniart — Fosdl Insects of the Primary Rocks. 483 



reasons, one is obliged to abandon tlie division into Mandibulata and 

 Haustellata. 



In 1863 Dr. A. S. Packard, jun., proi)Osed to create two series 

 among the insects : the Metabola and the Hetekometabola. In 

 this latter group he ranges the Coleoptera, Orthoptera, Neuroptera, 

 and Hemiptera ; bringing into the first group the Hymenoptera, 

 Diptera, and Lepidoptera. 



Mr. Samuel H. Scudder had the same idea in this respect as 

 Packard ; he created the names of Sternoptena (Metabola of Packard) 

 and of Gastroptena (Heterometabola of Packard). But the terms 

 employed by Packard seemed to him better fitted for general use, 

 and he has adopted them. 



Packard and Scudder start upon the principle that the more an 

 Arthropod has the three regions of the body (head, thorax, ami 

 abdomen) clearly distinct, the one from the other, the more it is 

 raised in organization. It is among the Hexapoda that this character 

 is most prominent : the Myriopoda, on the contrary, being the most 

 degraded in consequence of the great number of segments of which 

 the body is composed. The higher Crustacea and the Arachnida are 

 intermediate examples, for the head and the thorax are united, and 

 form the Cephalothorax. Among insects the component parts of 

 the thorax are more or less united together among themselves, and 

 those types whose thoracic segments are most united, and, con- 

 sequently, whose organs of flight are most nearly connected, must 

 be considered the most perfect. 



The Metabola are the Hexapoda which present this perfection in 

 the highest degree. They form unquestionably a more homogeneous 

 section than the Heterometabola, and are, moreover, of more 

 recent appearance on the surface of the globe. 



Let us then briefly state the principal characters of these two 

 great groups of insects, as Packard and Scudder have described 

 them : — • 



Metaeola. Heterometabola. 



Body clearly divided into three very Body divided into three parts ; the 



distinct parts (head, thorax, abdomen), three segments of the thorax are very 

 the three segments of the thorax closely distinct, 

 united together. 



Component pieces of the mouth ar- Mouth arranged generally for masticat- 



ranged, as a whole or in part, for suction. ing, rarely for sucking. 



Mandibles rarely opposed one to the Mandibles opposite one another, 



other. 



Anterior wings membranaceous and Anterior wings more or less coriaceous, 



much larger than the posterior, which with very numerous and strong nervures, 

 are sometimes rudimentary. generally longer and straighter than the 



posterior wings, or equal to them. 



Larva generally soft, not resembling Larva most frequently resembling the 



the adult. ■ adult. 



Pupa always inactive. Pupa active or inactive. 



Complete metamorphosis. Metamorphosis most frequently in- 



complete. 



Lepidoptera — Diptera— Hymenoptera. Hemiptera — Neuroptera— Orthoptera. 



It will be remarked that I have omitted to mention the Coleoptera, 

 which Scudder places among the Heterometabola ; but in my opinion, 



