364 



THE ANATOMY OF INVERTEBRATED ANIMALS. 



thorax are hardly distinguishable, and the abdomen has nine 

 visible segments. 



Fig. lOS.—Perla nigra.— k. The aquatic apterous larva. B. One of the transitional 

 stages between tbis and tbe perllct insect, C. ("' liegne Auiiual.'"; 



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

 are ametabolous. The majority have two pairs of simil-ir 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 Ort]ioi>tera ^ (the Termites, Cock- 

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



Fig. lOi.— Aphis pelarffonii. Apterous a2;amosenetic form. 



Earwigs) the mouth is constructed upon the same plan as 

 that of Blatta ; but the Physopoda or Tliysanoptera {JHinps 



J The Thyanmira and the Phympoda are often united with the Orthoptera 

 in modern e'lassitieations, while the Ephemeridoe and LibelluUdoe used to be 

 arranged with the i^turoftera. 



