130 



THE AMERICAN ENTOMOLOGIST. 



colored genus to which both insects belong 

 (Stisiis), but three species have hitherto been 

 discovered in North America. "We give in the 

 Appendix a description of a fourth species of 

 this same genus, the " Short-winged Digger 

 A7asp" {Stizushrevipennis, n. sp.), of which 

 but a single specimen exists in the cabinet of 

 the Senior Editor, and none at all, so far as is 

 known, in any other collection of insects. 



The holes or nests dug in the earth by Digger 

 Wasps arc, for the most part — especially in 

 loose, sandy soils — ^dug in the same manner as 

 Mr. Smith's Blue Wasp effaced all traces of its 

 nest, namely, by scratching with their front 

 legs, and scrabbling the loose dirt backward 

 with their four hind legs, the motions being 

 performed with the rapidity of lightning But, 

 as we saw above in the case of Dr. Packard's 

 and Mr. Holcomb's wasps, certain species occa- 

 sionally use their jaws in digging, and more 

 especially, perhaps, when the soil is hard and 

 solid; but, as a rule, they dig with their front 

 legs, and not with Iheir jaws, and scrabble the 

 loosened dirt backward with their hind legs. 

 Hence, we can see at once, why most species of 

 Digger "Wasps, and more particularly the 

 females, whicli have the actual work to do, have 

 their legs garnished plentifully— as has been 

 already stated, and as will be seen at once in 

 the wasps that are figured above — with long, 

 stiff bristles, or slender thorns. On the 

 other hand, the True "Wasps, which, M'hen 

 they dig at all, dig with their powerful jaws, 

 and not with their legs, have perfectlj' smootii 

 legs, as may be seen from the species figured 

 below (Figures 110, 111, 112). A European Dig- 

 ger Wasp, however, {Ammophila sabulosa) — 

 belonging to the same genus as our Painted- 

 wing Digger AVasp, (Fig. 100), which as we saw, 

 digs with its jaws and not with its legs — 

 although it has very bristly legs, is recorded as 

 using the long, sickle-shaped jaws, which arc 

 characteristic of the genus, both in burrowing 

 and in carrying the sand out of its burrow; 

 thus approximating the habits of the Digger 

 Wasps to those of the True Wasps.* So true 

 is it, that in Entomology there is scarcely a 

 single general rule without its exception, and 

 that, wherever we open the great Book of 

 Nature, and whether we study the structure of 

 insects, or their habits, we find almost every- 

 where intermediate grades, and connecting 

 links. 



The comparatively few Digger AVasps that 

 make their nests in timber, also have legs more 

 or less densely armed with the usual bristles and 



•See Westwood, Trmis. Entom. Soc. London, J, \i 200. 



thorns, because it is necessary for them to be 

 able to scrabble the minute fragments of wood 

 out of the holes, which they gnaw in the sub- 

 stance of the wood to serve as nests for their 

 larva?. In a single stick of partially decayed 

 firewood, we once found in the winter several 

 dozen of the nests of a small species of Wood 

 AVasp ( Crabro) . from which in the ensuing sum- 

 mer we bred about a dozen of the perfect 

 wasps. 



And now we approach a great mystery. The 

 genus of Digger Wasps linown as Pelopcpwf 

 (in English '•mud-maker''), to which appertains 

 the common Mud-dauber (Pe/ojm'us hniatux. 

 Fabr.) shown in Figure 104, and well known to 

 make the so-called •• nmd-dabs" so often found in 

 outbuildings, does not dig at all either in earth or 

 in wood." On the contrary, it constructs its 

 nests of tempered clay, affixing them to the in- 

 terior of any buildings to which it has free 

 access, or to overhanging clifl's. In search of 

 moist clay for this purpose, it may often be seen, 

 during a long diy spell of summer weather, 

 perched on the ground 

 in the neighborhood of 

 wells and other places 

 where water is habit- 

 ually slopped upon 

 clayey ground. We 

 should naturally ex- 

 pect, therefore, that, 

 as it has the same hab- 

 its as many of the 

 True AVasps, it would 

 have tlic .-mooth legs of a True AV"asp and not 

 those of a Digger AVasp. No such thing. The 

 legs of the female ilud-dauber arc obviously 

 bristly, though not so strongly as in the two 

 most nearly allied genera {Sphex and Ammoph- 

 ila), both of which arc known to burrow in the 

 earth. But why should they be so. when the 

 bristles arc of no manner of use to her, any 

 more than they would be to a True AA'asp? One 

 school of philosophers will reply, that its legs 

 arc bristly, because ages and ages ago, in the 

 dim far-away vista of bygone geological years, 

 the genus took its gradual origin from some 

 species that did really dig holes in the ground, 

 and had bristly legs to enable it to do so; and 

 that, in consequence of the disuse of its bristles 

 for generation after generation through myriads 

 of geological ages, the bristles themselves have 



•Tlu-i 



carulciis, 



Ni.rthi- 



iul>l.s at lirst sight the Blue Uig- 

 r Wasn liftiii-iit iiI)(im>, (Fii.'. '.i7). It may be readily distiu- 

 li.ihed, however Irom the latter, by the diffei-ent veining of 

 i front wings and by its smooth legs Respecting the mter- 

 inable coniusion among our different N. A. Blue Wasps, 

 e the Appendix. 



