348 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1953 



adapted for an aquatic life. The final extinct order, the Gloss- 

 elytrodea, appeared in the late Permian ; they were characterized by 

 highly modified elytra with unique venation. 



The living insect orders of the early Permian, in addition to the 

 roaches, comprised the mayflies, dragonflies, bark lice, true bugs, 

 flies, and Neuroptera. With the exception of the Neuroptera, these 

 Permian representatives were more generalized in most respects than 

 any existing members of their orders. The Permian mayflies, for 

 example, had homonomous wings, whereas in all living species the 

 posterior pair of wings are much reduced, both in size and venation. 

 The Lower Permian was apparently close to the time of origin of 

 most of these orders, for basic characteristics of related orders are 

 combined in some species. A surprising feature is that these first 

 insect representatives of existing orders are smaller in size than most 

 present species of their orders, and some of the fossil species are as 

 small as the smallest now living. 



Before the end of the Permian, three more living orders of insects 

 appeared. One of these, the stoneflies, included a species which can 

 be assigned with confidence to a living family. The other two orders 

 comprise the thrips and the beetles. The dominant insects of the late 

 Permian were true bugs, or Homoptera, which were clearly adapted 

 for feeding on plant juices. 



As is evident from this survey, the Permian insects were a remark- 

 able assemblage. During no other geological period has such a diverse 

 insect fauna existed. A striking contrast is found in the Triassic, 

 at the beginning of the Mesozoic, in which the disappearance of all 

 extinct orders, except the Protodonata, transformed the f acies of the 

 Triassic fauna to a semblance of that at present. True orthopteran 

 insects first appear in Triassic beds. Among them were several 

 species having well-developed stridulatory structures on the fore- 

 wings of the males. The insects had a wing expanse of about 9 inches, 

 and stridulatory area of the wing was fully as large as that in any 

 living insect, as shown in plate 1, figure 2. 



By the beginning of the Jurassic the Protodonata became extinct, 

 possibly because of the flying reptiles, or pterosaurs, which appeared 

 early in the period. Earwigs, caddis-flies, true flies, and the Hymen- 

 optera are found in middle Jurassic strata. The flies or Diptera were 

 almost exclusively midges or cranefly-like, there being none of the 

 higher Diptera, many of which are now conspicuously associated 

 with flowering plants. Similarly, the Hymenoptera were either rel- 

 atives of sawflies or parasitic types; the aculeates, such as bees and 

 wasps, were absent. Many of the Jurassic insects belonged to families 

 now living (see pi. 2, fig. 1). Looking at such specimens one finds it 

 difficult to realize that they were contemporary with the pterosaurs, 

 dinosaurs, and Archaeo'pteryx. 



