132 



THE AMERICAN ENTOMOLOGIST. 



the female of the wasp (Agenia hombycina, 

 Cresson), Figure 106, 6, thatconstractsit. From 



[Fig. 106.] 



Color.s— (n) clay-yellow; (6) dingy black. 



these four different kinds of mud-cells, we have 

 bred specimens of the four different species of 

 Spider Wasp {Agenia) that build them, three of 

 which are described species, and one {Ag. siib- 

 corticalis), a new and hitherto uudescribed 

 species. TMs last is con.'siderably the smallest 

 of the four, and its nest, which we have always 

 found exclusively under the loose bark of 

 standing trees, is sliowu in Figure 105, c. The 

 next largest species is one which was described 

 ^ thirty-two years ago by Thos. Say {Agenia 

 lljominlus] architectus) ; and it is very remark- 

 able that, although he gives a very elaborate 

 description of the mud-cells from which he bred 

 it, he says not a single word about the smooth- 

 ness of its legs, and refers it to the same genus 

 {Pompihis), to which belong the closely allied 

 species with strougly-armed legs. We may 

 add that Say found the mud-cells, from which 

 he bred his specimens of this insect, '•' under 

 prostrate logs and stones," while we found 

 our two mud-cells under the loose bark of 

 standing trees. The largest species but one 

 {Ag. mellipes), was described by Say at the 

 same time as the other one, merely from cap- 

 tured specimens, and without any knowledge 

 of its habits, or auy notice of its legs being 

 smooth. Tills species we have also bred from 

 mud-cells found exclusively under the bark of 

 standing trees. Finally, the largest species of 

 the four {Ag. hombycina), Figure lOG, b, was de- 

 sci-ibed only two years ago by Mr. Cresson, 

 without any knowledge whatever of its habits. 

 This last we have bred in large numbers 

 from mud-cells found under prostrate logs in 

 North Illinois, and four specimens fi-om similar 

 mud-cells found under the bark of a standing 

 tree in South Illinois. Unlike the other three, 

 it has very small rudimeutal spines — scarcely 

 perceptible except under the lens— on its legs. 

 In the Appendix will be found a full descrip- 

 tion of the new species of smooth-legged Dig- 

 ger Wasps referred to above, and a few other 



details relative to this singular geuus {Agenia), 

 which would not interest the general reader. 



It may be objected ijerhaps by the entomologi- 

 cal purist that, as all these builders of mu-dcells, 

 including the common Mud-dauber (Fig. 104) 

 never dig at all, either in the ground or in de- 

 cayed timber, or any where else, it is incorrect 

 to call them " Digger Wasps." But a general 

 name must not be changed because it is inap- 

 plicable to particular species. Many Bark-lice, 

 for example, do not inhabit the bark but the 

 leaves of plants ; for instance the Scale-insect 

 of the Oleander {Aspidiotus nerii, Bouche). 

 Yet this last is none the less a true Bark-louse 

 {Coccus family). Again, we have seen with 

 our own eyes the common Bed-bug {Acanthia 

 lectularia, Linn) actually swarming, not in beds 

 frequented by Christians, but in a chicken- 

 house. Yet auy i^recisian who should insist 

 that, when it infested a chicken-house, it ceased 

 to be a "bed-bug" and became a "chicken- 

 bug," would be simply ridiculous. Upon the 

 same principle, a smooth-legged Spider Wasp 

 does not cease to be a true Digger Wasp, because 

 it never digs. 



Not being aware of the habits of these small 

 smooth-legged Digger Wasps, any more than 

 anybody else, and being misled by certain mis- 

 statements as to the origin of our common 

 American "mud-dabs," Westwood has advanced 

 the erroneous opinion, that "it is only among the 

 Bees and (True) Wasps that we find the habit 

 of constructing nests with materials brought 

 from a distance."* This habit, it is true, is the 

 exception and not the rule among the Digger 

 Wasps. We find it more common among such 

 of the True Wasps as are solitary in their hab- 

 its. But when we come to the most intelligent 

 and highly-developed of the whole group — 

 namel}', such of the True Wasps as are social 

 and live in large communities — we find it uni- 

 versal. Undoubtedly this practice displays 

 great intelligence, and is as wonderful as the 

 proceedings of most birds in building their 

 nests with materials fetched from a distance. 

 It is interesting, therefore, to observe here and 

 there the first developments of this curious in- 

 stinct among the lower Wasps — its gradually 

 becoming more common among such Wasps as 

 approximate in. their organization to the Social 

 Wasps — and its full and complete culmination 

 among the latter, which are universally con- 

 sidered as the highest and most intelligent of all 

 the Wasps. 



The mud-daubing Spider Wasps {Agenia) are 

 not exempt from the attacks of parasites any 



* Introiluetion, n. p. 207. 



