THE WINGS OF INSECTS 401 



Wings of the Monarch Butterfly, Anosia plexippus. — Make a drawing 

 of each wing. 



Study the fore wing first. Figure 41 7 is a reproduction of a photograph 

 of a fore wing of a pupa of this species. In this figure the developing wing- 

 veins appear as pale bands and the trachea? as dark lines. A study of the 

 tracheation of this wing will aid in the determination of the wing-veins. In 

 one respect the branching of the radial trachea differs markedly from that of 

 the hypothetical type ; this feature is distinctively characteristic of the fore 

 wings of butterflies, it does not exist in moths. 



Determine the significance of the three short spurs that project into the 

 distal end of the large cell near the middle of the fore wing, the discal cell. 



Letter the veins of the hind wing, and the spurs that project into the 

 discal cell. 



Note the \-estige of the first anal vein at the base of cubitus. 



Fig. 417. — Wing of a pupa of the Monarch butterfly. 



The reduction of media. — In a few of the more generalized families of 

 the Lepdioptera the main stem of media is preserved ; this condition exists 

 in the wings Prionoxystus, already figured. But in most Lepidoptera the 

 base of media is wanting in the wings of adults, although the medial trachea 

 may be well-preser\'ed in the pupae ; this condition exists in the wings of the 

 monarch butterfly already studied. 



Correlated with the loss of the stem of media its branches become more 

 or less closely united with radius and cubitus. In the fore wing of the 

 Monarch Butterfly the base of vein M3 has moved towards vein Cui and 

 away from its former position indicated by a spur projecting into the discal 

 cell. 



WIXGS OF NEUROPTERA 



In the orders Diptera and Lepidoptera the more generalized members of 

 each order possess the maximtmi number of wing-veins found in the order. 

 It is those wings in which the maximum number of wing- veins exist that 

 most closely resemble the hypothetical primitive t}'pe of wing- venation ; 



