INSECTS AFFECTING PARK AND WOODLAND TREES 23 



oval eggs, which are usually deposited just behind the head of the victim. 

 It was formerly considered that such larvae were doomed, but more careful 

 investigations have shown that if the eggs are laid shortly before the 

 bearer molts, the skin may be shed before the grubs can hatch and pene- 

 trate the body of their prey. 



Prcdaccous insects. These are also valuable allies in controlling some 

 of our more important insect pests. The large social wasps are known to 

 prey to some extent upon the forest tent caterpillar, Malacosoma 

 disstria Hiibn., and the solitary wasps, Eumenidae, also attack various 

 forms. A large group of beetles, known as the Carabidae or ground beetles, 

 are almost entirely predaceous in habit, and undoubtedh' aid to a con- 

 siderable extent in reducing the number of various insects, particularly of 

 those species which descend to the ground at sometime during their e.xist- 

 ence. These beetles are very voracious and some of them are credited 

 with destroying many more insects than they can possibly devour. 



The Cleridae or checkered beetles are exceedingly valuable allies of 

 the lumbermen, since they occur very commonly on forest trees, particularly 

 on those infested with various bark and wood borers. It is by no means 

 uncommon to find their reddish, brown-headed larvae in the burrows of 

 such beetles as Tomicus and related genera, and considerable numbers of 

 adults may be observed on logs and trees badly infested with these 

 insects. Both adults and larvae are exceedingly voracious and undoubt- 

 edly accomplish much in controlling borers. 



The lady beetles, or Coccinellidae, constitute another exceedingly valu- 

 able group. The adults and the larvae are quite voracious, and are notable 

 for their fondness for various species of plant lice and scale insects. The 

 abundance of any members of these two groups is usually followed shortly 

 thereafter by the presence of a great many lady beetles and their young, 

 which feed on adults and young of the pests, and not infrequently do very 

 much toward reducing their numbers. 



There are a few of the darkling beetles, Tenebrionidae, credited with 

 being predaceous in habit and as these are found in decaying wood, it is 



