560 W. L. TOWER, 



lineata. In the wing there are three groups of veins each acting 

 as a unit ; an anterior set {sys. a) forming a strong costal border for 

 about two thirds of the costal edge and firmly fused with the articular 



coi: 



Fig. H. Hind wing of Leptinotarsa decem-linéata, folded, showing action of the 

 median system in folding the wing beneath the elytres as in Fig. G. 



head (cap.art); a middle system {sys.m) consisting of a single vein 

 which arises from the cotyla {cot) and ends in a transverse vein (6); 

 and a posterior system in the anal angle of the wing {sys.p) which 

 arises from the posterior side of the cotyla and is distributed to 

 the inner posterior part of the wing. 



In Fig. H is shown the development in the folded wing of 

 a joint in the costal edge at a, a fold in the wing parallel to the 

 transverse vein (?>), and a complex joint at d. Now by comparing 

 the anterior and posterior systems of Figs. G and H it is seen that 

 they remain unchanged in position in both figures but that the middle 

 system occupies a different position when the wing is closed from 

 that when the wing is expanded. The wing rotates upon the 

 cuticula head and when folded back beneath the wing covers the 

 inner end of the cotyla is brought into contact with a chitiuous 

 scalerite of the thorax which stops the further movement of the 

 cotyla medianward, and as the wing swings farther back the middle 

 system of veins is pushed outwards and anteriorly. This motion, com- 

 bined with the backward movement of the wing as a whole produces 

 the folding of the distal end of the wing as shown in Fig. H. There 

 are no traces of muscles or elastic ligaments in the wing which could 

 aid in the folding. Figs. G and H are camera drawings of wings and 

 show the actual position of the parts in the two conditions. 



