24 S. H. SCUDDER ON THE EARLY TYPES OF INSECTS. 



cockroach 1 has been described from the rocks of Saarbriicken, which are as old as any of 

 the insect-bearing beds of Europe. The insects of the middle Devonian of New Brunswick, 2 

 on the other hand, are known only by their wings and the most diligent examination of 

 thousands of fragments of shale has failed to reveal anything else. Further discussion of 

 this point may be dismissed with the remark that geological data are not likely to throw 

 much light upon it. 



It is of course of prime importance that we should understand the relative' subordination 

 of groups in insects, before investigating their order of succession in time. Many attempts 

 have been made to harmonize the current views- of their relative rank and geological suc- 

 cession ; but hitherto with indifferent success, mainly from the prevalence of the opinion 

 that Coleoptera were to be ranked highest among insects, while this suborder has been 

 known, from the first, to occur in Carboniferous strata, and some other suborders only much 

 later. Another obstacle which has stood in the way of a clear comprehension of the facts 

 has been the very common division of hexapod insects into two series, upon which the 

 English entomologists have perhaps specially insisted, called Mandibulata and Haustellata, 

 a division based upon inadequate physiological grounds. Or if it be maintained that the 

 function expressed in these names has a structural basis, it would be easy to point out that 

 in either of the two divisions the diversity of structure of the mouth parts is so great as to 

 admit of no common expression in other than physiological terms. If it were not so, the 

 claim made by Agassiz, 3 on embryological grounds, of a higher rank for the haustellate 

 insects would hold good, and we should be at a loss to account for the simultaneous appear- 

 ance of Coleoptera and Hemiptera. 



An apparently more rational division of the true insects into two series is that which 

 separates those with complete from those with incomplete metamorphosis ; the young in 

 the former case unlike, in the latter resembling, the parent. This however, taken abso- 

 lutely, separates closely allied groups, such as the caddice flies and dragon flies, and one 

 form of metamorphosis shades into the other ; moreover it allies the Coleoptera with the 

 Hymenoptera rather than with the Hemiptera or Orthoptera, and disaccords to so great a 

 degree with the general relations of structure among insects as to show that it cannot be 

 considered as of so fundamental an importance as we should suppose it would prove. Yet 

 it is an important factor in the life history of insects, and cannot be disregarded totally, as is 

 done in divisions based upon the mouth parts, but must be considered in any attempted dis- 

 tribution of the suborders. So too must the nature of the wings, for the possession of 

 wings is the preeminent characteristic of hexapods as a whole, and we should naturally 

 anticipate fundamental features in the differences of their structure. 



My own view of the primary relations of the suborders of hexapods was first expressed 

 by Packard in 1863, 4 when he said that Coleoptera, Hemiptera, Orthoptera, and Neuro- 

 ptera " seem bound together by affinities such as those that unite by themselves the bees, 

 moths and flies." To the latter or higher series he has since applied 5 the term Metabola 



1 (Polyzosterites granosus.) Goldenb., Faun. Sar. foss., i: 8 L. Agassiz. Classif. ins. ernbryol. data. pp. 4-8. 



18, pi. 1, fig. 17. 4 Packard. On synthetic types in insects. Bost. Journ. 



2 These Devonian insects, which were first briefly noticed Nat - Hist., vn : 591-92. 



by me in Bailey's Observations on the Geology of Southern 6 Packard. Guide to the study of Insects. Introduction. 



New Brunswick (8°. Fredericton, 1865) will form the subject 8° Salem, 1S69. In later editions these names are also in- 

 of a special paper now nearly completed. troduced in the text, on p. 104, with varying spelling. 



