Vol. 1.] Woodworth. — Wing Veins of Insects. 75 



into a corresponding hook of the front wing. A third method, 

 seen in such Heteroptera as Belostoma, consists of a i)air of pro- 

 jecting processes on the under side of the front wing near its 

 hind edge. These are of such shape and position that they 

 clasp around a thickened portion of the costal vein of the hind 

 wing. A similar method obtains in the Psocida^ but in some 

 instances in this group the normal structure is supplemented 

 or replaced by the clasp shown in Fig. 18. 



In the Lepidoptera a rather less efficient structure with the 

 same purpose is the frenulum. See Comstock ('93), Kellogg 

 ('95). In this group the coordination was probably at first 

 dependent on the overlapping of the wings. With the primi- 

 tive forms the wings were probably not particularly wide, so 

 that their overlapping involved a great loss of effective sur- 

 face. The development of the frenulum, which prevents the 

 wings being pulled too far apart, allows the reduction of the 

 overlap to a minimum. 



In any case the effect of coordination is to be seen in the 

 straightening of the adjacent edges of the wings, and a tend- 

 ency toward reduction in the number of veins of the adjacent 

 wing areas. In addition to this, there is the local specialization 

 of the coordinating organ. 



Another entirely distinct form of coordination is that which 

 exists between the two front wings in the Coleoptera and 

 Hemiptera. In both orders the coordination is brought about 

 to make the organ more efficient as a protection for the hind 

 wings when at rest, rather than to aid in flight. As the result 

 of this specialization in tlie Coleoptera the marginal vein of 

 the hind edge of the elytron becomes much enlarged and pecul- 

 iarly modified to form a catch, by means of which the two 

 elytra are held firmly together when at rest, tlie edge of the 

 wing at the same time having been so straightened tliat it 

 exactly meets the corresponding edge of the other wing through- 

 out most of its length. 



In the Heteroptera the marginal vein is also strongly de- 

 veloped, but not brought into such intimate relation to the 

 opposite wing. The most characteristic matter in this coordi- 

 nation is the structure of the apical third of the wing. This 

 region is so shaped that when at rest it exactly overlaps 

 in the two wings. As a consequence of this duplication there 

 is not the need of as much thickening of the membrane in this 



