HYMENOPTERA. 



In the geological stratum in which the first moths appear there are repre- 

 sentatives of most of the larger groups of Hymenoptera, indicating that it is 

 an older order. The structure of the lower forms shows a very close relation- 

 ship with the Lepidoptera and with the Trichoptera universally recognized 

 as the ancestor of Lepidoptera. From the same group the Hymenoptera must 

 also have sprung. The adult insect does not give any very clear evidence 

 of this or of any other relationship. 



Figure 53. Venation of tlie Honey bee. 

 The most distinctive structure is the dominance of three series of cross- 

 veins in the wing which render the venation difficult to interpret or compare 

 with other venations. The first series of cross-veins extends from the front 

 edge just before the node obliquely towards the base till it reaches the next 

 vein, then turns squarely towards the next vein beyond, marking off two 

 comparatively large basal cells. The second zigzags directly across the 

 wing touching the costa just beyond the node. The third is a little more 

 indeflnate. It is usually about midway between the second crossveins and the 

 tip of the wing. The usual conception of the venation hinges on the mar- 

 ginal cell, which is the large cell along the costa beyond the node. Below 

 this are two or three submarginal cells and the remainder of the closed cells 

 are called discoidal cells. The veins radiating from the marginal cell are 



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