634 EXTERNAL ANATOMY OF INSECTS. 



ably in different genera and species: upon these however 

 I shall not enlarge further, but proceed in the next place 

 to consider very briefly the wings of the Diptera Order 

 as to their neuration. These are not so easily made sub- 

 servient to a general plan. The basilar areolets are now 

 reduced considerably in length, occupying merely the base 

 of the wing a ; the medial are become less numerous and 

 important 15 ; and the apical, in a variety of instances, are 

 the most conspicuous ; in some wings, as in those of 

 Penthetria, the Intermediate Area has no nervures or 

 areolets, or only spurious ones; in Psychoda the nervures 

 diverge from the base almost without branching, so as to 

 form no closed areolets d ; in many, the lower medial 

 areolets are very long, resembling the basilar in Hymen- 

 optera e ; these are often crowned by a single small one, 

 as in the Stratyomida, Tipula, &c, from which nume- 

 rous branches proceed to the margin f ; but in Musca two 

 large ones approach the margin, the anterior one having 

 an angle open to it s ; in the Hippoboscidce almost the 

 whole of the wing is occupied by the apical areolets h ; 

 though in some cases they are incomplete '. 



4. I am next to consider the position of wings in repose 

 and their folding. The most important object of this is 

 that when unemployed they may occupy less space, be 

 less in the way of the insect, and be most effectually pro- 

 tected from injury. Another end is also served by this 

 structure, — that wings can thus be very ample, and pre- 



1 Plate X. Fig. 12, 15, e: " Ibid. Fig. 15./-. 



c Ibid. Fig. 12. g-. <* ibid. Fig. 13. 



e Ibid. Fig. 15. c. f Ibid. d. 



e Ibid. Fig. 14. e. h Leach on Eproboscideous Insects, 



Mem. Wern. Soc. 1817- i. xxv.f. 3, 5, 8, &c. 

 '' Ibid, t.xxxif.J, 10, 13. 



