126 GENERA OF HYMENOPTERA. 



Family VESPID^. 



This family compi'ise the Social Wasps, commonly known as 

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

 preceding by the two-s]inrred intermediate tibise, and simple tarsal 

 claws. They are all i)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 pulp, which they after- 

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

 that fijrm the material of their nests," which are found generally sus- 

 pended from the branches of trees, and sometimes in the cornel's 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 Polistes, 

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

 sessile or subj)etiolate 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 Ve>ij)a. There do not appear to 

 be any well-marked distinguishing characters between the females 

 and workers of Polisfes, and probably also of Polijhia, which differs 

 only in the form of the abdomen. 



The characteristics of the genera belonging to this family are as 

 follows : 



Table of Genera. 



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

 cate ; the basal nervure joins the subcostiil norvure some distance before 

 the stigma Vespa Linn. 



Abdomen subsessile or subpctiolate, loii^', fusiform ; metathorax as long as broad, 

 oblique above: the basal nervure joins tlic subcostal iicrvurc at base of the 

 stigma ■'oliMtes Latr. 



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

 neuration much as in PoUstes. l*oI,vl>ia St. Farg. 



Our s[)ecies of this fiimily tire in much confusion, and need a thor- 

 (^iigli revision. The species of Polides ai'e exceedingly variable, and 

 there is no doubt that a careful study of a large collection of si)eci- 

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



Pohjbia has but a single representative in our \\\\\ui\, jlaviixirsk 

 Sauss., quite a common insect in California. 



