16 



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



The exceptions in the former group are only in the Hymenoptera, which usually have 

 mandibles well developed for opposing each other. In the latter, more heterogeneous 

 group, the exceptions are more abundant. In the Coleoptera the metamorphosis is com- 

 plete. 1 In the Hemiptera, the mandibles are developed as needles and with the other 

 parts of the mouth form a sucking tube ; in many of them also the front wings are almost 

 wholly membranous. The Neuroptera, using the term in the Linnaean sense, are the 

 least amenable to law ; their fore wings are usually membranous, though the veins are gen- 

 erally thick and approximated ; a few (Ephemerina) have small hind wings ; many of them 

 show the regional divisions of the body almost as strikingly as the Metabola, although the 

 abdomen is generally developed to an excessive extent, and in such insects the prothorax is 

 not greatly developed ; while, as before stated, part of them have an incomplete metamor- 

 phosis, and so have been classed with the Orthoptera by the later German writers, and others 

 have an incomplete metamorphosis. The structural affinities, however, of the Neuroptera 

 proper and the so-called Pseudoneuroptera are so close that they cannot be disconnected, 

 notwithstanding the striking differences in general features between them ; and although, 

 thus composed, the Heterometabola exhibit anomalous features in nearly every suborder 

 contained in it, we must accord to this division of hexapods into Metabola and Hetero- 

 metabola a closer connection with all the facts than any that has yet been proposed. 



How closely this division accords with the geological succession of insects will appear 

 from the fact that all the suborders of Heterometabola, and none of Metabola are repre- 

 sented in the palaeozoic rocks. 2 This is the more striking from the fact that, if we omit 

 mention of the single discovery of insect wings in the Devonian, the three orders of in- 

 sects, — hexapods, arachnids and myriapods, appear simultaneously in Carboniferous strata. 3 



1 It would appear, at first sight, as if Dr. LeConte, in his 

 Classification of the Coleoptera of North America (8°. 

 Washington, 1861), Introduction, p. 8, held that Coleoptera 

 were to be ranked as the highest suborder among hexapods. 

 His table would seem to indicate this ; but he speaks with 

 hesitation, as if proposing only a provisional arrangment, 

 remarking : " We can merely state in general terms that 

 those [hexapods] having a perfect metamorphosis are the 

 highest ; and those having the thoracic segments agglutin- 

 ated, or the prothorax separate, are to be considered above 

 those in which the larval character of similarity among the 

 thoracic segments is preserved." To the first proposition 

 no one will take exception ; the latter ought to be restricted 

 in its application to those groups only to which the Cole- 

 optera are most nearly related, viz.: to the other Hetero- 

 metabola ; so far as they are concerned this would seem to 

 be an indication of special and therefore comparatively 

 high structure ; but otherwise, as a mark of inferior organ- 

 ization, since it is opposed to the progress of structure seen 

 throughout the articulates, marked by a condensation, so to 

 speak, of the thoracic segments. Many Neuroptera and 

 Orthoptera, notably such forms as Corydalis and Forficula 

 (the latter classed by early writers with Coleoptera), show 

 in their prothorax a close resemblance to Coleoptera ; and 

 the very size and importance of this segment in Cole- 

 optera, when the whole hexapod series is taken into ac- 



count, should therefore be looked upon as a sign of rela- 

 tively low rank. I am pleased to be able to state, from a 

 recent conversation on this point with Dr. LeConte, that he 

 did not intend to extend the argument drawn from the pro- 

 thorax over the whole hexapod series, but only over those 

 most nearly related to Coleoptera, and purposely expressed 

 himself in guarded language. 



2 No generalization so broad as this and at the same time 

 correct has yet been made. Many authors indeed, and not- 

 ably Bronn, dividing the hexapods into two series, — Mandi- 

 bulata and Suctoria (or equivalent terms) — claim that the 

 carboniferous hexapods were all biting insects, and that the 

 sucking insects first appeared in the Jura. The latest state- 

 ment of this sort was made by Haeckel (Gen. Morph. 

 Organ., n, p. xcix, 1866), but Dohrn's Eugereon was 

 published in the same year, and by the light of this strange 

 insect many palaeozoic insects now appear, as I shall en- 

 deavor to show below, under an entirely new aspect, and 

 render it probable that there were many, as there certainly 

 were some, sucking insects in palaeozoic times. 



8 Carboniferous arachnids have been described by 

 Corda, Fric, Ilarger, Meek and Worthen, Koemer, Seud- 

 der,and Woodward; while myriapods from the same form- 

 ation have been described by Dawson, Meek and Worthen, 

 Scudder, and Woodward ; besides others from other palaeo- 

 zoic beds by Dohrn and Geinitz. 



