DISTRIBUTION OF INSECTS. 283 



&c. — are accordingly not true Orthoptera, but orthopteroid Palaeo- 

 dictyoptera; the Carboniferous and Devonian netted-veins not true 

 Neuroptera or Pseudo-Neuroptera, but neuropteroid PalEeodictyop- 

 tera, and, similarly, the Hemiptera (Eugereon, Fulgorina), hemipte- 

 roid Palaeodictyoptera. Apart from the contradictory conclusions 

 which have been reached from the study of these forms by Hagen, 

 Gerstaecker, Eaton, and others, it may be reasonably doubted 

 whether the extreme specialisation seen among the Pateodictyoptera 

 will carry out the inference that the larger groups of Paleozoic times 

 were more closely related to one another "than any one of them 

 is to that modern group to which it is most allied, and of which it 

 was with little doubt the precursor or ancestral type.""' Surely, 

 it will not be contended that Palephemera and the highly special- 

 ised Titanophasma are more nearly related to each other than they 

 are to the modern families Libellulidse and Phasmidae, not to men- 

 tion the orders to which these belong ; and if this be so, why 

 should they be referred rather to the one loose comprehensive group 

 than to the several groups which they immediately represent ? 



The remains of beetles (Coleoptera), if we except the very 

 doubtful Troxites (which is considered by some naturalists to 

 represent the fruit of a plant), are unknown in the Paleozoic depos- 

 its ; but it is by no means unlikely that the members of this order 

 had already existed, since borings in wood, very like those made 

 by the coleopteroid larva, have been discovered in various localities.* 



The Triassic insect fauna, wliich is represented by some four or 

 five European species, and by about twenty in America (Colorado), 

 is almost exclusively orthopteroid, and exhibits a distinct passage 

 between the ancient and modern types of cockroaches — Palaeoblat- 

 tarise and Blattariae. The first indisputable beetle (Chrysomelites), 

 followed by several highly differentiated types in the Rhsetic — 

 Hydrophilites, Buprestites, Curculionites — is found in the deposits 

 of this age. No truly metabolous insects, or those undergoing 

 complete metamorphosis, other than Coleoptera, are known before 

 the Lias, where, however, we have several sjiecies of Diptera 

 (Chironomidis, Tipulidse), and at least one representative of the 

 Hymenoptera, an ant (Palaeomyrmex prodomus), from Schambelen, 



i * Different coleopteroid species have at various times been described from 

 Carboniferous strata, but these are now known to be mainly referable to the 

 Arachnida or spiders. 



