44 OUR SHADE TREES AND THEIR INSECT DEFOLIATORS. 
under loose bark. Both spiders are wonderfully active, and kill large 
numbers of caterpillars. Their large flat egg-masses can be found dur- 
ing the winter under dead bark and in cracks. Both species hibernate 
in silken nests in similar localities.” . 
PREDACEOUS INSECT ENEMIES. 
The caterpillars of this moth have quite a number of external ene- 
mies, which slay large numbers of them. The well-known Rear-horse 
(Mantis carolina, see Fig. 20) seems to be very fond of the caterpillars. 
Fic, 20.—Mantis carolina: a, female; b, male. 
The so-called Wheel-bug (Prionidus cristatus, see Fig. 16) has proved to be 
one of our best friends in reducing the numbers of the caterpillars. This 
insect was formerly by no means very common in cities, but of late years 
it has greatly increased in numbers, and is now a well-known feature in 
all our public parks and such streets as possess shade-trees. Outside 
of the city it is rarely met with; nor does it extend much farther north 
than Washington. It is, like the Mantis, in all its stages a voracious 
feeder upon insects, slaying alike beneficial and noxious ones. The 
bright red larve and pupe, also carnivorous, are seen in numbers dur- 
ing the summer; they usually remain together until hunger forces 
them to scatter. They assist each other in killing larger game, and are 
to this extent social. The Wheel-bug could be observed almost any- 
where last summer, usually motionless, stationed upon the trunk of 
trees, waiting for the approach of an insect. If one comes near, it 
quite leisurely inserts its very poisonous beak, and sucks the life-blood 
of its victim. When this becomes empty it is hoisted up in the air, as 
if to facilitate the flow of blood, until eventually it is thrown away as 
a mere shriveled skin. The appetite of the Wheel-bug is remarkable, 
whenever chances offer to appease it to the fullest extent. Frequently, 
