HYMENOPTERA 369 



made of a grayish paper composed of fibers of weather-worn but not de- 

 cayed wood. This paper is comparatively strong, so that the envelope 

 of the nest is composed of sheets of paper of considerable size, a single 

 sheet often completely enveloping the nest. The wasps which build this 

 type of nest are commonly known as hornets. 



The other kind of nest is built in a hole in the ground, which is en- 

 larged by the wasps as they need more room for the expansion of the 

 nest. The paper of which these nests are made is brownish in color and 

 is made out of partially decayed wood; it is very fragile and would not 

 be suitable, therefore, for use in nests built in exposed places. Even 

 though the nest is built in a protected place, the use of this fragile ma- 

 terial necessitates a different style of architecture. The enveloping layer 

 of the nest, instead of being composed of sheets of considerable size, are 

 made up of small, overlapping, shell-like portions, each firmly joined by 

 its edges to the underlying parts. The wasps which build these under- 

 ground nests are commonly known as yellow-jackets. 



It has been found that at least two species of this subfamily are 

 social parasites. In these species the worker caste has been lost, there 

 being only males and females. The female enters the nest of another 

 species of Vespa and lays her eggs, and her larvas are reared by the right- 

 ful owners of the nest. 



The members of the social hornets and yellow-jackets found within 

 the limits of our territory are commonly included in a single genus, Vespa. 

 Only a few of our species can be mentioned here. 



The giant hornet, Vespa crabro. — This is our largest species, measur- 

 ing about f of an inch in length. It is brown and yellow in color and is 

 found around New York City, on Long Island, and in Connecticut. It 

 builds its nests in hollow trees and within buildings suspended from the 

 roof. It came to this country from Europe. 



The white-faced hornet, Vespa maculata. — This is the common, large 

 black and white hornet. It is widely distributed in the United States 

 and Canada. The nest, which is sometimes very large, is usually attached 

 to the limb of a tree. 



A common yellow-jacket, - Vespa maculifrons. — This is one of the 

 common species that builds its brown paper nests in the ground or be- 

 neath some object on the ground or, occasionally, in a stump. In the 

 height of the season there may be several hundred individuals in a nest 

 which they will defend against an intruder with wild fury. Another 

 common yellow-jacket is V. diabolica with similar nesting habits but 

 which also, at times, builds aerial nests. 



THE DIGGER-WASPS OR SPHECOID WASPS. 



The wasps in this group are perhaps more properly known as sphecoid 

 wasps but since most of them make nests for their young by burrowing 

 in the ground or in wood they may very properly be called digger-wasps. 

 There are three families in the group of which the first, Ampulicidas, is 

 small and its members rare; the second, Dryinidse, is composed of para- 

 sitic forms; and the third, Sphecidae, is a large one and contains many 

 species of varied habits. 



