No. 376.] THE WINGS OF INSECTS. 243 
cipal veins. This, however, is not true of all psocids. In some 
the bend in the media does not reach the radial sector, and the 
two are connected by a radio-medial cross-vein. 
The margin of the adult wing is tubular throughout, there 
being what has been termed by writers on the Diptera an 
ambient vein. The costal and anal portions of this doubtless 
represent the costa and third anal veins, respectively, although 
the corresponding tracheze are apparently lost. The distal 
portion of this ambient vein was preceded by the anastomosing 
tips of all of the veins, as is shown in the figures of the nymph 
wings. In the fore wing the tip of the subcosta coalesces with 
the radius; in the hind wing it coalesces with the costa. In 
the fore wing a large stigma is developed in an angle of vein 
#1; and in both wings the anal furrow coincides with the first 
anal vein. 
IV. THE VENATION OF THE WINGS OF A CICADA. 
A study of the wings of Hemiptera reveals remarkable 
departures from the primitive type of wing venation. So great 
are these that, at first, one sees very little in common between 
the wings of a bug and those of insects of any other order. 
We were filled with delight, therefore, when we found within 
this order, preserved almost unchanged, what we had come to 
regard, from a study of other orders, as the primitive type of 
wing venation. 
The conservative Hemiptera that retain most perfectly the 
fashions of ancient times, so far at least as concerns the vena- 
tion of the wings, are the cicadas. But the slightness of the 
changes that have taken place is not obvious if one studies 
only the wings of the adult; for in this stage there is a massing 
of several veins along the costal margin of the wing, and the 
cross-veins have the same appearance as the branches of the 
primary veins. 
In the wings of a young nymph, on the other hand, the 
trachez that precede the primary veins are not massed as they 
are later, and in the older nymph where the forming veins 
appear as pale bands the cross-veins contain no trachez. 
