THE SPRUCE INVESTIGATION. 267 



ovipositors. They are among the principal enemies of the bark 

 and wood mining insects, and are entitled to high rank among 

 the friendly insects of the spruce. The eggs are deposited near 

 or in their victims by means of their ovipositors, which are 

 inserted through the bark. As a rule the Braconid larva at- 

 taches itselt to the side or back of a bark or wood mining larva, 

 which is soon rendered inactive from the loss of life sustaining 

 liquid or blood. It then ceases to feed and soon dies. The 

 parasite maggot continues to feast on its dead victim, and in a 

 few days attains its full growth. It then encases itself in a 

 thin but tough cocoon, which completely fills the cavity previ- 

 ously occupied by its victim. In this cocoon it goes through its 

 transformations, and when the adult i& fully matured, it gnaws 

 its way out through the bark. 



CHALCID PARASITES. 



The Chalcids which are also four-winged insects and related 

 to the wasps and bees, differ from the Ichneumonid and Braco- 

 nids in having shorter and more compact bodies ; also in the 

 color, which is usually bright shining blue, green, bronze, or 

 black, often with hyaline or metallic reflections. The wings, 

 instead of having numerous veins as in the two former families, 

 are veinless or have but few. They also show a marked differ- 

 ence in the antennae, which in the former families are long, 

 slender, while in the Chalcids they are short, often club-like 

 and elbowed. They are also distinguished by the form of the 

 hind femur which is often very much thickened for leaping. 

 The ovipositor of the female is usually concealed beneath the 

 body and is much shorter than in most Ichneumonid and 

 Braconid parasites, so that they are not capable of penetrating 

 very thick bark, but usually select that on young trees or the 

 branches of old ones, unless the insect they seek to attack 

 works in the outer portion of the inner bark and makes its 

 pupa cases in the outer bark, as does the destructive spruce 

 bark beetle. 



The Chalcids are common parasites of the bark beetles in all 

 kinds of trees, and especially so in spruce and pine, and as I 



