INTRODUCTION 



mere fold of the membrane ; (2) stalking, when two veins are 

 fused together for a portion of their length from their base, so 

 as to appear to rise on a common stalk ; (3) coincidence, when 

 two veins are fused together for the whole of their length, so 

 that oue appears entirely absent, an extreme form of stalking ; 



(4) anastomosis, when two veins rise separate, meet and are 

 fused together for a certain distance, and then separate again ; 



(5) concurrence, when a vein rises separate, runs into another, 

 and does not separate again, an extreme form of anastomosis ; 



(6) connection, when two veins are connected by a short trans- 

 verse bar passing from one to the other, a special form of 

 anastomosis, evolved from the ordinary form under the influ- 

 ence of a tendency to lateral extension. Vein lb in both 

 wings is often furcate at the base. 



The type of veins in the Micropteryrjina differs from that 

 described above in two essential particulars, viz. (1) there may 

 be three additional veins in the forewings, rising out of vein 11 or 

 12 ; and (2) the veins of the hind wings are practically identical 

 in number and structure with those of the forewings, being 

 thus much more numerous than in the ordinary type. There 

 is also often a system of cross-bars between the veins near the 

 base of the wing. 



The structure of the veins can be best observed on the 

 under- surface of the wing, where they are more prominent. 

 The student should begin by completely denuding of scales 

 a few wings of common species ; the wing should bo cut off 

 and laid on a moistened piece of glass, to which it will adhere ; 

 the scales should then be removed, first from one surface and 

 then from the other, with a fine moist camcl's-hair brush, an 

 operation requiring a little patience and delicacy of touch ; the 

 veins will thus bo rendered conspicuous. When, however, the 

 student has familiarised himself with the general subject, it 

 will not be found necessary in practice to resort to this process ; 

 most details will be easily observed without denudation ; where 

 this is not the case (as where the veins are closely crowded or 

 otherwise obscured), the scales can be removed with the brush 

 on the under-surfaco in the locality of the difficulty only, 

 without cutting off the wing or otherwise damaging the speci- 

 men, which remains in the collection available for all purposes 

 as before ; with proper practice, even the smallest species are 

 amenable to this treatment, which docs not require more skill 

 than the actual setting of the specimen. Somo workers prefer 

 to put a drop of benzine on the spot, which renders it tern- 



