(512 PnOCEEDINGS OF THE NATIONAL MUSEUM. vol. xxix. 



veined wings would seem to indicate that the extra veins are a hin- 

 drance rather than an aid in stili'ening the wing. This is continued bj 

 t\w fact that they have been suppressed. If these superfluous veins are 

 a hindrance in the foi'uiation of trusses, they are also in the way in 

 the development of wing furrows as will be seen by an examination 

 of any of these or similar generalized forms. In the generalized 

 wings the wing furrows are straight folds, permitting of only the 

 minimum amount of Hexibility, while in BJennocampa (tig. 72), 

 Lycdota (tig. 55), and Lah/darge (tig. 78), they have been developed to 

 their full extent. These wing furrows are undoubted!}- the primary 

 factor in eti'ecting the suppression of such veins as the radial cross- 

 vein, the radio-medial cross-vein, and the free part of R. in the front 

 wing; and the transverse part of M, the free part of R^, and the trans- 

 verse part of Mg in the hind wing. The way in which the radial 

 furrow has etiected the radial ci'oss-vein is seen in the wings of Dineura 

 (tig. 63), and Rhadlnocerxa (tig. 70), where the cross-vein is gradualh^ 

 losing its chitinization through the prominence of this fui-row. The 

 etiect of the median furrow on the radio-medial cross-vein is seen in 

 the wings of Euura^ Pteronux (tig. 6S), Cladlns (tig. 66), and PrU- 

 tipliorn. In this latter genus there exist all stages from a fully pre- 

 served radio-medial cross-vein to its entire disappearance. In the 

 genera Monoeteiiux (tig. 67) and Lophyriis (tig. -15) an intermediate 

 sidewise development is shown in certain species where only the pos- 

 terior half of the cross-vein has atrophied, while the anterior half is 

 fully preserved. 



That the loss of the free part of Cu.> is due to the anal furrow is 

 seen by an examination of the wings of the following genera in the 

 order named: Buctroceroa (tig. 41), PamphilluH (tig. 39), Ce]>Jiale!a 

 (fig. 4:2), Lyda (tig. 37), Csenolyda (tig. 38), and Itycorsia (tig. 40). In 

 these genera there is a complete series from a fully formed Cu2 to a 

 miiuite swelling on the side of Cu. The anal furrow is the most 

 important as well as the most prominent and persistent furrow found 

 in either wing. It is found in the saiue position throughout the entire 

 order Il^'menoptera. It is this furrow that furnishes the tiexibility 

 in movement between the two wings. Cu.>, having been separated 

 from the anal veins by this furrow, could be of only secondary impor- 

 tance in supporting this area; in fact it is more efficiently supported in 

 the wing of BJennocampa without it than it is in the wing of Bactroceros 

 with it. The series here named shows that we have a gradual move- 

 ment toward the assumption of the condition found in Blenrt(teamj>a. 

 This is shown in the straightening of that part of cubitus situated 

 l)etween the medio-cubital cross-vein and the base of the wing, and 

 the migration of the anterior end of the medio-cubital cross-vein from 

 a union with media to a union with radius, by this movement coming 

 into direct line with the subtransverse part of radius. Correlated 



