90 Annals Entomological Society of America [Vol. VI, 



traversed (Fig. 20). In this condition they join first anal just 

 before that vein unites with cubitus at its distal end. 



This represents the normal procedure. It is not strange 

 to find, however, in a reduced wing, that this region is subject 

 to more variation than that of any of the other veins. In some 

 species, for example, third anal never appears in the adult wing 

 and the cell 2nd A is absent. This has been brought about 

 either by the atrophy of third anal or by its coalescence for an 

 entire instead of a partial length with second anal, the latter 

 explanation being perhaps the more reasonable. vSince this 

 condition is found principally in the wings of the smaller 

 species such as Micrutalis calva, Stictocephala liitea, and Cyr- 

 tolohus vau (see figures 33, 31, 43) it is probably due to the 

 lack of development of this part of the wing, which causes a 

 crowding of the tracheae cephalad. In other forms third anal 

 breaks away from second anal after anastomosing for some 

 distance, and sends a very short portion out through the 

 membrane to the margin of the wing. This is found mainly 

 in the larger wings, where there is more surface to be supported, 

 being best seen in the fore wings of Thelia bimaculata, Telemona 

 ampelopsidis, and Platycotis sagittata. 



Cross-veins 



Of the cross-veins which appear in the fore wing, three only 

 are constant and characteristic of the family, the others being 

 peculiar to certain genera and species and of little comparative 

 importance. 



The first of these characteristic cross-veins is found connect- 

 ing R2+3 with R4+5, dividing the cell R3 at about one-third its 

 length from the point of branching of radial sector. It is 

 fairly constant, but it does not appear in the genera Acutalis 

 or Micrutalis in so far as representatives of these genera have 

 been studied. In the figured wing of Ophiderma pubescens q. v., 

 this cross-vein is forked, a condition which is of course abnormal. 



The second is equally constant but surprisingly variable in 

 position. It appears between media and cubitus, usually in the 

 basal third of the wing, but often shifts from a position close to 

 the base of these veins (cf. Ceresa diceros) to one so far toward 

 the tip of the wing that in the case of Smilia camelus (see figure) 

 it has actually moved off of cubitus and its posterior end 

 rests on the other cross-vein which connects Cu with M3+4. 



