624 EXTERNAL ANATOMY OF INSECTS. 



from the base of the wing : in many, as in Pterophylla K., 

 the part of the wing lately alluded to, that is longer than 

 the tegmen, and of the same substance, points out the limit 

 of the Costal Area ; and in others this part terminates in 

 a segment of a circle and is differently reticulated at the 

 apex from the Intermediate : in the Homopterous Hemi- 

 ptera and the Libellulina, in which the areas at first seem 

 indistinct, they may generally be easily traced by follow- 

 ing them from the axes. The separation of the Costal 

 from the Intermediate in the remaining Orders seems less 

 easy on account of the branching of the nervures : in the 

 rest of the Neuroptera and the Lepidoptera, if the poste- 

 rior branches of the postcostal nervure are not included, 

 you will have a narrow Postcostal Area, which in most 

 cases forms an angle more or less prominent, in Corydalis 

 almost a right angle, with the Intermediate: in Hemerobius 

 and affinities this part is distinguished by areolets form- 

 ed by transverse nervures, while those of the rest of the 

 wing are lo?igitudinal z : but if the posterior branches are 

 included, the Costal Area will be more ample : a similar 

 observation applies to the Hymenoptera and Diptera ; in 

 these, in all cases, the areolets adjoining the anterior mar- 

 gin, which follow the stigma, should be regarded as be- 

 longing to the Area in question b . In those tribes of the 

 former Order, whose wings are without nervures, the 

 areas are often marked by folds. 



M. Chabrier has observed that in Coleoptera the spe- 

 cific weight of the margin of the wing, and its means of 

 resistance, are augmented by a liquid which is introduced, 

 at the will of the animal, into a long pocket under the 



a Plate X. Fig. 7. h\ r. k: h Ibid. Fig. 8. 9. 12. a *. 



