EXTERNAL ANATOMY OF INSECTS. 615 



and the membrana is a very narrow strip ; in L. apterus 

 the former are very faintly traced out, but they are pre- 

 sent in all those that are furnished with wings ; whence 

 we may conjecture that they are of the same importance 

 in flight with the folds observable in those organs a . The 

 three basal areas may be said most commonly to present 

 three isosceles triangles, the Costal one being narrow and 

 curvilinear b , the Intermediate the most ample c , and the 

 Anal one the narrowest and shortest d , with its vertex to- 

 wards the apex of the Hemelytrum, while in the two former 

 it is at its base. In Lygceus compressipes {TUiinuchus 

 K. MS.) the Anal Area is cultriform; and in most of the 

 Hydrocorisce it has an angle in the middle of its posterior 

 margin. The proportion that the membrana or apical area 

 bears to the rest of the wing varies in the different tribes. 

 In some, as before stated, it is obsolete, in others nearly 

 so ; in the majority, perhaps, it occupies about a third of 

 the hemelytrum ; in Lygceus compressipes, cruciatus, &c, 

 full half; in Alydus calcaratus, two-thirds ; in Reduvius, 

 nearly three-quarters e ; and in Aradus depressus the cori- 

 um, — divided, however, though indistinctly, into the three 

 areas, — is driven to the base of the wing : two ends are 

 answered by this structure — as this insect lives under 

 bark, its thin hemelytra take less room ; and as it flies, 

 though it has only rudiments of wings, they are more fit 

 to supply their place : the part we are speaking of usually 



Ion Latr., agrees with Latreille's description in all respects, except 

 that it cannot be said to be membrana nulla apicali. 



a Chabricr Analyse, &c. 24. h Plate X. Fig. 3. b: 



c Ibid, e: "' Ibid, d: 



c Plate XXVIII. Fig. 23./"' is the corium and g" the membrana 

 of a species of Reduvius F. 



