3l8 AN INTRODUCTION TO THE STUDY OF FOSSILS 



each surrounds itself with a brown case (pupa case), from which 

 it bursts a week later as a full-grown fly. 



The generalized structure of the early insects indicates that 

 the various individuals were more similar to one another than at 

 present. They combine in the same individual characters which 

 are now found only in distinct families and even orders. Insects 

 are known from the Pennsylvanian to the present. 



The following are some of the localities where the delicate 

 bodies of insects, arachnids and myriopods occur well preserved : 

 Pennsylvanian of Commentry, central France; Saarbriicken, 

 southwestern Rhenish Prussia ; Mazon Creek, Illinois ; Rhode 

 Island Coal Measures ; Jurassic of Solenhofen, Bavaria ; 

 Oligocene of East Prussia and Baltic amber ; Miocene of Oenin- 

 gen, Baden, on Lake Constance, and that of Florissant, Colorado. 



Derivation of name. — Latin in, into, + secare, to cut. Origi- 

 nally named from such forms as bees and wasps, which are al- 

 most completely cut into two or three parts. 



Summary of the Orders of Insecta 



I. Paleodictyoptera (Pennsylvanian). These are possibly 

 the ancestors of all winged insects. 2. Mixotermitoidea (Penn- 

 sylvanian). 3. Reculoidea (Pennsylvanian). 4. Protorthoptera 

 (Pennsylvanian and Permian). 5. Orthoptera (Jurassic to 

 present) ; e.g. grasshoppers, crickets. 6. Phasmoidea (Jurassic 

 to present). 7. Dermaptera (Eocene to present). 8. Diplo- 

 glossata (living). 9. Thysanoptera (Eocene to present). 

 10. Protoblattoidea (Pennsylvanian and Permian). 11. Blat- 

 toidea (Pennsylvanian to present). These, the cockroaches, 

 were exceedingly abundant in the upper Paleozoic coal swamps. 

 12. Mantoidea (Permian to present). 13. Isoptera (Eocene 

 to present) ; e.g. white ants. 14. Corrodentia (Oligocene to 

 present); e.g. book lice. 15. Mallophaga (hving) ; e.g. bird 

 lice. 16. Siphunculata (Uving). 17. Coleoptera (Jurassic to 

 present) (Fig. 137). Beetles. 18. Hymenoptera (Jurassic 



