THE HYMENOPTERA 



343 





One of the stem borers attacks currant stems. The adult girdles the stem after 

 laying its egg, and the larva feeds below the girdled place, which shows plainly, 

 the part above wilting or breaking over. Cutting off such stems as soon as they 

 are seen, eight or ten inches below the girdled place, will control this insect. 



Most of the borers of this superfamily which tunnel in wood are 

 generally called Horn-tails, the straight, stiff ovipositor somewhat 

 suggesting a horn. Various trees, both deciduous and evergreen, are 

 attacked by different species, and the circular exit holes of the borers 

 after they have become adult permit the entrance of moisture and the 

 spores of fungi, thus providing starting places for decay. Healthy, 

 vigorous trees are seldom attacked, but the death of others is hastened 



by these insects. One species 



known as the Pigeon Tremex 

 (Tremex columba L.) bores in the 

 maple, apple, pear, elm, beech, oak 

 and sycamore. It varies from 

 three-quarters of an inch to twice 

 as much in length (Fig. 358) and 

 its body is cylindrical and nearly 

 as large as a lead pencil. Its color 

 varies from nearly black with 

 yellow spots on the abdomen to 

 yellow with some black marks. 

 This insect is often noticed on the 

 tree trunks during the summer 

 months. The larva tunnels its 

 course through the wood, going 



sometimes several inches into the tree, but as the end of its feeding 

 period approaches, turns outward and makes a hole to the outside, 

 leaving only a thin piece of bark to close the opening. It then goes 

 back into the hole a short distance to pupate and the adult on emer- 

 gence gnaws away the piece of bark and escapes from the tree. An 

 interesting and remarkable looking parasite of this insect will be considered 

 later in the chapter. 



Superfamily Ichneumonoidea (The Ichneumon Flies). In this very 

 large and important group the insects have the abdomen constricted as 

 already described, between the propodeum and the second abdominal 

 segment. In one family (the Evaniidae or Ensign flies) of rather small 

 insects (Fig. 359) the petiole of the second segment does not join the pro- 

 podeum near the lower side of the body but near the upper surface, giv- 

 ing these insects a very peculiar appearance. 



The Ichneumon flies (Fig. 360) are all parasites, attacking Lepidop- 

 tera, Coleoptera, Diptera, and some Homoptera ,Orthoptera and Hymen- 



FTG. 358. Pigeon Tremex (Tremex columba 

 L.), somewhat reduced. (Original.) 



