THE AMERICAN ENTOMOLOGIST. 



133 



more tli:m any other group of insects. From a 

 lot of the kinil of mud-cells sketched in Figure 

 1(1."), c, we long ago bred great numbers of a mi- 

 nute Chalci!i6y {I'teromalus) only one-twentieth 

 of an inch long; and from a lot of those shown 

 in Figure 105, a, about a dozen specimens of a 

 beautiful undescribed Ichneumon-fly, about one- 

 Ihird of an inch long, banded with black and 

 white, and with a white horse-shoe on the hind 

 part of its thorax, to which we have given the 

 manuscript name of the Horse-shoe Ichneunion- 

 fl y {Mesosten usferrum-equinum) . 



It is well known to entomologists that among 

 the solitary Bees — whos^e habit it is to provision 

 their nests with pollen, and not, after the fashion 

 of the Digger AVasps and solitary True Wasps, 

 with living insects — there are many genera, 

 physically incapacitated from collecting pollen, 

 xvhirh lay their eggs surreptitiously in the nests 

 of the true pollen-collecting Bees, and thus ap- 

 propriate for their own ofl'spring (he rich stores 

 laid up for another's. Not only in the case of 

 the group of Spider Wasps just now referred to 

 (Ai/enia), but in that of several other genera of 

 Digger Wasps {Tnjpoxylon, relojxeus and 

 Sapyga) , has a. similar habit been inferred by 

 several authors to prevail. ^Vo suspect that, in 

 these particular cases, erroneous inferences have 

 been drawn from seeing the supposed Guest 

 Wasps entering old last year's nests made by 

 true Digger Wasps, or by Bees, which nests 

 they afterwards appropriate for their own use, 

 having first in many instances repaired and re- 

 modeled them. As regards the first of the three 

 genera enumerated above {Trypoxylon), West- 

 wood has shown this to be so;* and, at the risk 

 of being tedious, we will give some additional 

 proofs of this and certain other analogous fiicts. 

 which have been observed by ourselves for a 

 long series of years. 



Almost every American knows the so-called 

 " mud-dabs," constructed by the common Mud- 

 dauber (Fig. 104), to be composed of one or more 

 layers or tiers of clay tubes, arranged side by 

 side like a set of " Pan's pipes," and cemented 

 on to some surface pretty well protected from 

 the weather. In a particular locality — the rocky 

 clifts near Black Hawk's Watch-tower, in Rock 

 Island county. Ills. — we liave always, for many 

 years back, found these '• mud-dabs" to contain 

 in the winter months the cocoons of the wasp that 

 makes them, and those of another Digger Wasp 

 of a uniform black color, and belonging to a very 

 distinct family {Trypoxylon albitarse, Fuhr) . 

 Figure 107, promiscuously intermixed in about 

 equal proportions. There ran be no mistake 



•• Inlroduclion, &c.. II., p. 194. 



Culc.i-s— l'oli.slK-il.,ljhick, with till, hin.l p.iws wliiti^h. 



here, because the cocoon of the former, after 

 stripping off the thin semi-opaque flossy outer 

 membrane, characteristic of all those made by 

 Digger-wasps, is about eight-tenths of an inch 

 long, elongate oval, five times as long as wide, 

 of a shining transparent taAviiy color, as thin 

 almost as gold-beater's skin, and with the tail 

 end docked, tliickened and blackened ; while 

 the cocoon of the latter has a mere vestige of 

 outer membrane, and is only about half an 

 inch long, only thrice as long as wide, cylindri- 

 cal but often with the head end expanding, like 

 a cooper's rivet, into a more or loss wide flange, 

 of a dnll opaque black color except the head 

 end, which is ash gray, with the tail end docked 

 but not otherwise ditt'ering from the rest of the 

 cocoon, and the whole of a pretty firm and solid 

 consistence. lu most cases the elongate mud- 

 cell of the Mud-dauber, when it has been ten- 

 anted by the Black Wasp spoken of above, is 

 partitioned off by a clay diaphragm in the mid- 

 dle into two cells, each of which contains a dis- 

 tinct cocoon ; but occasionally such a cell con- 

 tains but a single cocoon, especially wheu the 

 cell is rather shorter than usual. It is well 

 known that the Mud-dauber provisions its nest 

 with spiders, and fragments more or less com- 

 plete of spiders may often be found in the cells 

 occupied by its cocoons. Precisely the same 

 thing occurs iu the cells tenanted by the cocoons 

 of the Black Wasp, showing that its larva must 

 have fed upon spiders just as does that of the 

 Mud-dauber. Lastly, from the cocoons shaped 

 like a cooper's rivet, isolated in a separate ves- 

 sel, we have i-epeatedly bred, not the Mud- 

 dauber (Fig. 104) , but the Black Wasp (Fig. 107) . 

 Now, here is a mass of evidence amounting 

 to what lawyers would call prima facie proof, 

 that this Black Wasp is really a Guest-wasp, 

 not building and provisioning any nest for itself, 

 but laying its eggs in the nest built and provis- 

 ioned by the Mud-dauber, and thus fraudulently 

 appropriating for its own future progeny, the 

 provision of spiders, laid up for the progeny of 

 the Mud-dauber, by that poor hard-working in- 

 dustrious insect. Otherwise, whv should the 



