244 NORTH AMERICAN INSECTS. 



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Saw-wasps (Tenthreds). 



These insects are distinguished by the double saw at the 

 extremity of the hind body, with which all the females are 

 provided, and with which they cut, like a carpenter, little 

 slits in the stems and leaves of plants, into which they drop 

 their eggs. The larvas of the Saw-wasps exactly resemble 

 caterpillars, and they feed upon the leaves of those plants 

 upon which their mother had glued her eggs, that is, upon 

 which they were born. They cast their skin four times, 

 and, when fully grown, some species go into the ground in 

 order to make their cocoons ; while others metamorphose 

 and fasten their cocoons on the stem of a plant, like the 

 caterpillars of butterflies. 



The ELM-TREE SAW- WASP (Cimbex Ulmi) is one of the 

 largest insects of this family. It is about one inch long, 

 and its wings expand about two inches. Its head and tho- 

 rax are black, the hind body blue, the antennae of a nankeen 

 color toward the top and dusky at the base, the feet pale 

 yellow, and the legs black. The female may be seen de- 

 positing her eggs, early in June, upon elm-trees, the leaves 

 of which serve as food for the insect and her offspring. 

 The caterpillars which issue from these eggs are of a green- 

 ish-yellow color, and have twenty-two legs. When fully 

 grown, they descend from the tree, conceal themselves under 

 the fallen leaves on the ground, and there spin their cocoon, 

 within which they remain during the whole winter, and 

 until the following May or June, when the perfect insect 

 makes its exit. 



The Wood-wasps are the most destructive insects of this 

 whole order, and often do great injury to our forest, as well 

 as our ornamental and fruit trees. Perhaps the most con- 

 spicuous insect of this species in this countiy is 



The PIGEON TREMEX (Tremex Columba), Fig. 69. This 

 insect is more than one inch long, and, like the whole fam- 



