Vol. 1.] 



Woodivorth. — ^Ying Veins, of Insects. 



35 



species, Cicada tihicen, is not greatly different from the Euro- 

 pean insect studied by him. In this insect the metathorax 

 has been very much reduced, the hind wings being scarcely 

 more than appendages to the anterior pair, and having very 

 feeble, if any, motion of their own. Only in the front pair do 

 we find the articular structures in a truly functional condition. 

 We therefore will not concern ourselves at this place with a 

 comparison of two segments, but confine our consideration to 

 the attachments of the anterior wings. 



■ FIG. 12. Mesothorax of Cicada tibicen, showing wing attachment. 

 A, from the side. B, section. 



dm, depressor muscle; em, elevator muscle; wr, wing-root; 

 awr, anterior wing-root; pwr, posterior wing- root. 



At the outset we are confronted with a fact which can not 

 but have a powerful influence in shaping the structure at the 

 base of the wing. It is what is known as the flexion of the 

 wing, a motion by means of which that organ is made to lie 

 along the side of the body when at rest. This flexion, even in 

 a small insect possessing a wing much constricted at base, can 

 not be sufficiently provided for by the simple elasticity of the 

 parts, because the bending must be nearly at right angles to 

 the path of vibration, and so across the breadth of the wing, 

 and because the flexed position must be that of rest. A 

 rearrangement of certain of the basal structures is thus 

 necessary. 



The harvest fly will serve as a type of insects with flexible 

 wings (see Fig. 59). In this insect there is a rather rigid wing- 



