74 AN INTRODUCTION TO ENTOMOLOGY 



The median furrow is usually between radius and media. 



The nodal furrow is a transverse suture beginning at a point in the 

 costal margin of the wing corresponding to the nodus of the Odonata 

 and extending towards the inner margin of the wing across a varying 

 number of veins in the different orders of insects. 



The axillary furrow is a line that scr\-es as a hinge which facilitates 

 the folding of the posterior lobe of tlie wing of many insects under that 



part of the wing 



\ \ ^\^ J^C^~'*"^^~"'~~''"~->-.^^^^^ wing where they 



VJ^---__X,^ ^X/^"^---^..^ ^^^"--~~ y^ are crossed by 



^^^"~~--~_N_____;;i----'''^''^ furrows. The 



^. „„ „,. , ,, . bullee are usually 



Pig. 88. — -Wings of Myrmecia; b, b, b, bullae. . . , 



paler m color 



than the other portions of the wing ; they are common in the wings 



of the Hymenoptera (Fig. 88), and of some other insects. 



The ambient vein. — Sometimes the entire margin of the wing is 

 stiffened by a vein-like structure; this is known as the ambient vein. 



The humeral veins. — In certain Lepidoptera and especially in the 

 Lasiocampidas, the himieral area of the hind wings is greatly expanded 

 and in many cases is strengthened by the development of secondary 

 veins. These are termed the humeral veins. 



The pterostigma or stigma. — A thickened, opaque spot which 

 exists near the costal margin of the outer part of the wing in many 

 insects is known as the pterostigma or stigma. 



The epipleurcB. — A part of the outer margin of the elytra of beetles 

 when turned down on the side of the thorax is termed the epipleura. 



The discal cell and the discal vein. — The term discal cell is applied 

 to a large cell which is situated near the center of the wing; and the 

 term discal vein, to the vein or series of veins that limits the outer end 

 of the discal cell. These terms are not a part of the uniform terminol- 

 ogy used in this book, and can not be made so, being applied to 

 different parts of the wing by writers on different orders of insects. 

 They are included here as they are frequently used, as a matter of 

 convenience, by those who have adopted the uniform terminology. 

 The discal cell of the Lepidoptera is cell R+M + lstM2; that of the 

 Diptera is cell ist M2; and that of the Trichoptera is cell R2+3. 



