XIII. Winged Insects from a Paleontological Point of View, or the Geological 



History of Insects. 



By Samuel H. Scudder. 



Read April 1, 1885. 



A HE division of hexapod insects into orders has undergone no very striking changes 

 since the time of Linne and Fabricius, the founders of entomological science ; new ele- 

 ments, indeed, have entered into their definitions, but the main divisions introduced by 

 these pioneers have, on the whole, stood the test of time and increasing knowledge in a 

 somewhat remarkable way. Unquestionably this is due in large measure to a somewhat 

 unusually sharp delimitation of most of the main groups, recognized even by the least 

 observant, who, if given a thousand chance insects from his own neighborhood, would be 

 pretty sure to separate from one another the wasps, the moths, the flies, the beetles, etc., 

 or at least most of them. There are, of course, a few forms (few, compared to the mass) 

 which would prove disturbing elements, and there are some concerning which the best 

 informed are not wholly agreed. There are also some groups about whose taxonomic 

 value there is still disagreement, such as whether the Heteroptera and Homoptera should 

 be looked upon as orders or as primary divisions of the order Hemiptera ; others con- 

 cerning which there is some dispute whether they should be separated as orders, or as 

 mere families of one of the long established orders, instances of which may be found in the 

 Westwoodian orders of Aphaniptera and Euplexoptera; still others, not regarded as dis- 

 tinct orders, concerning whose nearest affiliation there is or has been question — as in the 

 case of the so-called Pseudoneuroptera. This is in effect only to say that here, as in 

 other great zoological divisions, there are aberrant groups, and the main groups them- 

 selves are unequally delimited. 



The attempts, however, to group the orders into larger divisions still subordinate to the 

 grand hexapod type have resulted in very diverse presentations, according as one or 

 another set of organs, or other peculiarities, were deemed of prevailing weight. The two 

 which have found the most adherents have been that which separated the mandibulate 

 from the haustellate insects, and that which divided them from each other according as 

 their metamorphosis is complete or incomplete. To the first, the objection naturally arises 

 that it places the Hemiptera beside the Hymenoptera, Lepidoptera and Diptera, rather 

 than with the Coleoptera and Orthoptera, to which by all other points in their bodily 

 structure and by their metamorphoses they are certainly far more closely allied. To the 



