354 



APPLIED ENTOMOLOGY 



the larva of the Cuckoo Wasp may eat the host or it may consume the 

 food stored there, thus starving the proper inmate of the cell. Adult 

 bees and wasps know these enemies of their young and sometimes drive 

 them away from their nests, though frequently without success, the Cuckoo 

 Wasp watching its chance to return later unobserved. Taking into con- 

 sideration the nature of the hosts of the Chrysids it is probable that as 

 a whole the group should be considered injurious rather than beneficial. 



Superfamily Sphecoidea (The Digger Wasps). The insects of this 

 group vary much in size, some being very small while others, particularly 

 tropical species, may be more than an inch and a half long. Some of 

 them are bright-colored, yellow, orange, green and black being the more 

 usual colors, and the wings are frequently smoky and with an iridescent 

 luster. A functional sting is present. 



FIG. 370. FIG. 371. 



FIG. 370. Bembecid Wasp (Bembidula quadrifasciata Say), natural size. (Original.) 

 FIG. 371. Sphccid Wasp (Sceliphron ccemcntarium Dm.), natural size. (Original.) 



Some of the insects (Fig. 370) in this superfamily (Families Bembecidse 

 and Cerceridse) have the petiole connecting the mass of the abdomen 

 with the propodeum very short, but in the others (Fig. 371) it is long and 

 slender, the entire first segment behind the propodeum and sometimes 

 a part of the second being very slender and elongate. These insects are 

 often spoken of as the " thread- waisted wasps." 



The digger wasps are all solitary in their habits. The females of 

 many species dig holes in the ground, in some cases several inches deep: 

 others dig out the pith in plant stems: still others make nests of mud, 

 gathered where there is moist earth, placing them under projecting 

 stones, under eaves of buildings or in houses where access is easy through 

 open doors or windows: in some species the nest is excavated in wood, 

 and a few kinds have either not developed the nest-making habit or have 

 lost it and use holes or the deserted nests of other species for themselves. 

 In many instances the nest is subdivided into chambers separated from 

 each other by partitions of mud. 



Wherever the nest, and whatever the material which composes it, 

 its purpose is the protection of the young of the insect and of the food 



