216 TOWARDS THE HUMAN FORM 



Neuroptera and Orthoptera, existed; for instance, Protophasma 

 dumasi had the body of Phasma and the four large flat 

 wings of the Neuroptera, whereas Phasmas to-day are wingless 

 or have very small anterior wings and posterior wings folded 

 fan-wise. This last character, which is nowadays common to 

 all Orthoptera, was lacking in their ancestors, whose posterior 

 wings, scarcely larger than the anterior, remained flat when 

 at rest. Finally, in certain forms traces have been recognized, 

 or claimed as recognizable, of a pair of wings on the prothorax, 

 which is innocent of wings in present-day forms. This confirms 

 the opinion previously expressed that the wings were at first 

 epipodites, or dependences of the legs, since each of the 

 segments provided with legs could also be provided with wings. 

 But the most astonishing thing about the Insects of the 

 Carboniferous Period, which have been studied so carefully 

 by Charles Brongniart, is the size to which they attained. 

 Titanophasma fayoli achieved a length of twenty-eight centi- 

 metres ; certain Dragon-flies had a wing-span of seventy 

 centimetres, and the wings of a species of Ephemeridae of the 

 genus Meganeura measure no less than thirty-three centi- 

 metres in length. This great size was a characteristic no 

 doubt of certain species only, though very large Phasmids, 

 Cyphocrana, for instance, and very large Scarabs, Dynastes 

 and Goliath, still live in hot countries. But the fact merits 

 no less attention on that account. To-day the life of Insects 

 is short ; it hardly exceeds a year except for those larvae which 

 live sheltered under the ground like those of the Cockchafer 

 or Cicada, or in tree-trunks like those of the Stag-beetle and 

 large Capricorn-beetle, or in waters that do not freeze, like 

 those of our large Dragon-flies. These larvae live three 

 or four years. There is an instance of a Cicada in the United 

 States x which will live underground for as many as seventeen 

 years. It is so largely a question of shelter that longevity 

 increases considerably in adult Insects living in social groups, 

 and having arrived at the building of common homes, such 

 as Termites, social Wasps, Bees, and Ants. This leads us to 

 conclude that brevity of life in Insects has been caused by the 

 annual variations of temperature, which brought periodically 

 excessive cold in winter or excessive rains in summer. These 



1 Cicada septemdecim. 



