CHAPTER XIII 



Order Hymenoptera 



The few leaf-miners of this order all belong to the single 

 family of sawflies, Tenthredinidae. It is a large family of 

 rather primitive forms for the most part given over to 

 general leaf -feeding. 



In manner of life there is an interesting parallelism be- 

 tween these lowly Hymenopterous miners, and the primi- 

 tive Lepidopterous ones of the family Eriocraniidae. In 

 both groups apparatus is developed for inserting eggs in the 

 leaf tissue. The eggs of the two groups are similarly large 

 and membrane-covered and swell after insertion to twice or 

 more the original size. Even the mines of the two groups 

 are strikingly alike — blotched, transparent, with some of 

 the fibrovascular system removed and with a large amount 

 of excrement. Representatives of both groups are to be 

 found mining in the early spring before most other miners 

 appear. In the rapid feeding up, in leaving the mine, in 

 entering the ground, in spinning the cocoon, there is a great 

 similarity. In both, the feeding period is short — hardly 

 more than two weeks; in both, the pupal period is short — 

 something less than a month; in both, the adults live but a 

 few days; and in both, a very large part of the year is spent 

 as inactive larvae in a silken cocoon in the ground. Eco- 

 logically the two groups are remarkably exact counterparts. 

 The eggs. Many of the leaf-mining sawflies, in common 

 with the remainder of their family, have the habit of insert- 

 ing their eggs in the interior of leaves. A cut is made for 

 each egg separately through the leaf epidermis not infre- 

 quently in the axil of a lateral vein. The egg-slits are made 

 by the ovipositor of the female operating in much the fashion 



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