210 



THE WINGS OF NEUROPTERA 



In addition to the five longitudinal veins that have been retained there 

 are many marginal accessory veins ; these are especially well developed in 

 the spatula when this part of the wing is broad (Fig. 207). 



There is one feature in the venation of the fore wings that merits fuller 

 discussion than is given in the general statement given above, that is the 



Fig. 209. — Part of a hind wing of Nemoptera sinuata. 



probable method of increase in the number of the branches of the radial 

 sector. In Nemoptera (Fig. 206), the radial sector is four-branched; as 

 this is the typical number of branches, there is no difficulty in determining 

 their homologies; they are doubtless veins R5, R4, R3, and Ro respectively, 

 as is indicated in the figure. But each of these branches is deeply forked; 

 and it is obvious that if the splitting of the branches were carried much 

 farther the number of the branches of the radial sector would be increased 

 by the interpolation of branches, instead of by the addition of branches at 

 the distal end of the series, which is the more usual method. 



The probability that the addition of branches to the radial sector in this 

 family is by the interpolation of branches makes it difficult if not impossible 

 to determine the homologies of the branches when there are more than four 

 of them; in such cases, the branches may be ntmibered (Fig. 207 and 208). 



In having the number of the branches of the radial sector increased by 

 interpolation, the Nemopteridse resembles the Dilaridse. In this respect 

 the family Nemopteridse differs from the other members of the myrmeleonid 

 group of families, and the Dilaridae from the other hemerobiid families; 

 each of these cases is an illustration of the fact that in the order Neuroptera 

 different families exhibit very different methods of specialization of the 

 wings. 



(u) THE WINGS OF THE APOCHRYSID^ 



The type of wing-venation characteristic of the Apochrysidae is exhi- 

 bited by the wings of Apochrysa croesus (Fig. 210). This is one of the most 

 beautiful of neuropterous insects, with a wing expanse of 65 mm.; it is 

 found in Japan. 



In general appearance the wings of this insect bear some resemblance to 

 those of Chrysopa; but when they are carefully studied they arc found to 

 present the essential features of the wings of the myrmeleonid group of 

 families. 



