364 



THE ANATOMY OF INVERTEBRATED ANIMALS. 



thorax are hardly distinguishable, and the abdomen has nine 



visible segments. 



Fia. 103. — Terla nigra. — A. The aquatic apterous larva. B. One of the traneitional 

 BtageB between this aud the perfect iusect, C. (" Kegne Animal.") 



The Orthoptera (Fig. 103) and the Hemiptera (Fig. 104) 

 are ametabolous. The majority have two pairs of similar or 

 more or less dissimilar wings in the adult state, and in the 

 apterous forms it is probable that the wings are aborted, not 

 typically absent. In the Orthoptera'^ (the Termites, Cock- 

 roaches, Grasshoppers, Crickets, Day-flies, Dragon-flies, and 



Fio. lOi.— Aphis pdargonii. Apterous agamogenotic form. 



Earwiirs) the mouth is constructed upon the same plan as 

 that of Blatta; but the Physopoda or Thysanoptera (Thrips 



» The Thysanura and the Phywpoda are often united \rith the Ortloptera 

 in modem classifications, while the Fphemerida and Libellulidce used to be 

 arranged with the JWurojpUra. 



