48 AN INTRODUCTION TO ENTOMOLOGY. 



two orders of biting insects there can be but little doubt that certain members 

 of the Orthoptera (the crickets and katydids) reach a higher specialization in 

 structure than do any of the Pseudoneuroptera. The Physopoda are undoubt- 

 edly lower in structure than the Hemiptera; but they resemble that order 

 more closely than any other in the structure of the mouth-parts. The deter- 

 mination of the proper sequence of the orders of the Metabola is a much more 

 difficult question than that of the Ametabola. Of the five orders which con- 

 stitute the higher series, entomologists are agreed that the Neuroptera are the 

 lowest in structure. The Hymenoptera are placed highest with almost equal 

 unanimity ; not only do these insects exhibit a very high degree of organiza- 

 tion, but the development of the instinctive powers reached by bees, wasps, 

 and ants is greater than that attained by any other insects. The Lepidoptera 

 are placed next to the Neuroptera on account of the affinities between the cad- 

 dice-flies and moths. On the other hand, the higher Lepidoptera and the Dip- 

 tera resemble each other in the structure of the thorax. And the pupae of 

 certain Diptera (Cecidomyidae and Tipulidae) resemble more or less the pupae 

 of Lepidoptera. The Coleoptera are assigned to the next highest place, with the 

 belief that their complexity of structure entitles them to this rank ; but with 

 no intention of suggesting affinities with the Hymenoptera on the one hand 

 or the Diptera on the other. 



Following the tabular statement of the more important charac- 

 ters of the orders of insects, there is given a table to aid the student 

 in classifying specimens. This table is purely artificial and includes 

 only adult insects. I have endeavored, however, to include in it all 

 of the aberrant forms, those which the young student would find 

 difficult to classify. 



TABULAR STATEMENT OF THE MORE IMPORTANT CHARAC- 

 TERS OF THE ORDERS OF HEXAPODA. 



A. Wingless insects which show no evidences of having descended from 

 winged ancestors {i.e., in which the thorax is simple in structure), and which 

 undergo no metamorphosis. (Synaptera.*) I. THYSANURA. 



AA. Winged insects; or wingless insects in which this condition is the result 

 of a retrograde development, indicated by the complicated structure of the 

 thorax, or by the presence of wings in closely allied forms. (Pterygogenea^) 

 B. Insects with an incomplete metamorphosis. (Ametabola^) 

 C. Mouth-parts formed for biting ; i.e., with the mandibles and maxillae in 

 the form of jaws. 

 D. The two pairs of wings similar in structure, membranous. 



II. PSEUDONEUROPTERA. 



DD. The first pair of wings parchment-like; the second pair membra- 

 nous, and folded in plaits longitudinally. III. ORTHOPTERA. 

 CC. Mouth-parts intermediate in structure between those of the biting 

 insects and those of the sucking insects viz., with bristle-like mandibles* 

 and with flat, triangular maxillae. IV. PHYSOPODA. 



