. The theory of evolution in the light of facts. Fig. 7.—Beetle Fig. 8. — Primary Wood Fig. 9.—Dragon-fly (Jura). Wasp (Jura Hymenoptera). (Jura). Figs. 7-9. [After Handlirsch.) insect orders with their subdivisions have arisen bydifferentiation of one original type. This occurredthrough changes in the originally similarly segmentedbody—for instance, in the Beetles and Hymenoptera,into three clearly divided main sections : head, breast,and rear segments. Other recent offshoots, hke theTermites, show a still more uniform segmentation ofthe whole body. In the Thysanura this is forma
. The theory of evolution in the light of facts. Fig. 7.—Beetle Fig. 8. — Primary Wood Fig. 9.—Dragon-fly (Jura). Wasp (Jura Hymenoptera). (Jura). Figs. 7-9. [After Handlirsch.) insect orders with their subdivisions have arisen bydifferentiation of one original type. This occurredthrough changes in the originally similarly segmentedbody—for instance, in the Beetles and Hymenoptera,into three clearly divided main sections : head, breast,and rear segments. Other recent offshoots, hke theTermites, show a still more uniform segmentation ofthe whole body. In the Thysanura this is formation of the anteunse, also the number oftarsi and the venation of the wings afford opportunities ?• Die Umschau, p. 590. , KESULTS OF PALiEONTOLOGICAL EESEARCH 41 enough for specialization and particularly also theformation of the jaws, which are already differentiatedfor masticating, stinging, sucking, etc. In many cases the speciahzation was associatedwith regression, with reduction of the number of wingsand segments. As an extern
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