6o POPULAR SCIENCE MONTHLY 



the Mesozoic, or the age of reptiles. Of its three chief divisions, 

 Cretaceous, Jurassic and Triassic, the first mentioned and youngest 

 has thus far yielded only a small number of fossil insects. During the 

 Cretaceous, the flowering plants came into existence, and on this ac- 

 count it may be concluded that a multitude of new conditions were 

 furnished for many kinds of insect forms. The bees and various other 

 honey-eaters could thus have originated. The fact that insects imme- 

 diately adapted themselves to these new plants is to be seen in the few 

 specimens thus far obtained; that is, in the galls and eaten places on 

 the leaves of the oak, willow and Eucalyptus, etc. Other than these, 

 unfortunately, but little evidence of insects has been found in the 

 Cretaceous. 



On the contrary, the remains of this group preserved in Jurassic 

 deposits are very large in number. These have been discovered in 

 England, Spain and Eussia, but nowhere in such quantities and re- 

 markable preservation as in the Jura of Franconia in northern Bavaria, 

 where in previous epochs a shallow sea between coral reefs became 

 filled up with the finest calcareous silt. Many of the insects which 

 peopled the neighboring land found their graves in this mud. By a 

 fortunate chance, after perhaps millions of years, these forms have now 

 come to us, for this same hardened mud is to-day used by us as litho- 

 graphic stone or paving-stone. 



Now what does this rich collection of Jurassic insects teach us? 

 It shows that in that period probably an entire series of groups of 

 living forms either then had no existence or were just in the process 

 of evolution. As yet are found no locusts, no earwigs, termites, thrips 

 and wood-lice. Of the Diptera, the only representatives are those 

 which are in the minority to-day ; of the Hymenoptera, the wood-wasp, 

 saw-fly and ichneumon-fly alone appear to have been present, while 

 bees, ants, etc., are wanting. Some primitive forms of butterflies have 

 been discovered, but these were at first erroneously regarded as cicadas. 

 Grasshoppers were abundantly developed and some of them, judging 

 from the structure of their legs, may have run about on the water or 

 wet mud quite as water-striders, a genus of aquatic insects, do at the 

 present time. Through their changed habits of living, these water 

 locusts thus appear to have modified the legs no longer needed for 

 jumping, and in this way the specters, or walking-sticks, may have 

 finally originated. Dragon-flies, May-flies, Neuroptera and Hemiptera 

 were represented in great variety, and of the last group there were 

 aquatic species as well as those terrestrial ; also small cicadas. Beetles, 

 too, were not wanting, although no particularly striking forms are to 

 be distinguished. 



The fact that Jurassic insects were so extremely abundant clearly 

 indicates a warm climate, and the school children of Bavaria would 



