126 GENERA OF HYMENOPTERA. 



Family VESPID^. 



This family comprise the Social Wasps, commonly known as 

 "Hornets" and "Yellow-jackets," and is easily separated from the 

 preceding by the two-spurred intermediate tibiae, and simple tarsal 

 claws. They are all ])aper-makers, not out of rags, but out of wood, 

 and according to Walsh, " alighting upon some wooden surface ex- 

 posed to the weather, they gnaw off with their strong jaws the minute 

 filaments of wood, which have become partly detached by the action 

 of the elements, and chew them up into a fine pulj), which they after- 

 wards spread out into thin sheets of strong, gray, weather-proof paper 

 that fi)rm the material of their nests," which are found generally sus- 

 pended from the branches of trees, and sometimes in the corners of 

 outbuildings. Some species, e. g. the " Yellow-jackets," as previously 

 noticed, build their nests underground and presumably much on the 

 same principle as those built above ground. The species of Polides, 

 which differ by the more slender form, longer metathorax and sub- 

 sessile or subpetiolate abdomen, build combs or a series of paper cells 

 in various sheltered places, principally on the roof-timbers of barns 

 and other outbuildings, but always without an envelope or covering, 

 as is used by most of the species of Vespa. There do not appear to 

 be any well-marked distinguishing characters between the females 

 and workers of Polides, and probably also of Polyhia, which diflers 

 only in the form of the abdomen. 



The characteristics of the genera belonging to this family are as 

 follows : 



Table of Genera. 



Abdoiiicn sessile, broad and truncate at base ; metathorax very short and trun- 

 cate; the basal nervure joins the subcostal nervure some distance before 

 the stigma Vespa Linn. 



Abdomen subsessile or subpetiolate, long, fusiform ; metathorax as long as broad, 

 oblique above : the basal n§rvurc joins the subcostal nervure at base of the 

 stigma Polistes Latr. 



Abdomen petiolate, short and ovate beyond the first segment ; metathorax and 

 neuration much as in Polistes Polybia St. Farg. 



Our species of this family are in much confusion, and need a thor- 

 ough revision. The species of Polistes are exceedingly variable, and 

 there is no doubt that a careful study of a large collection of speci- 

 mens will result in a marked reduction of the number of species. 



Polybia has but a single representative in our fauna, fiavitarsis 

 Sauss., quite a common insect in California. . 



