WHEELER— THE PARASITIC ACULEATA. 17 



" The inference is unavoidable — more especially as we had previously 

 bred very numerous specimens of the same little mud-dauber from the same 

 kind of mud-cells obtained in northern Illinois — that this gaily dressed 

 Spider wasp (Ccropalcs) had sometime in the summer of 1867, laid an egg 

 in one of the five mud cells found in south Illinois, and thus appropriated to 

 the use of its future larva the supply of food laid up by the provident care 

 of the unfortunate, dingy looking little mud-dauber for its own offspring. 

 Otherwise it is impossible to account for two distinct kinds of wasp hatching 

 out from the same lot of mud cells." 



Perez (1894) and Ferton (1897) made some very interesting 

 observations in France on the behavior of Ccropales maciilata and 

 cribrata, showing that these wasps are parasitic on various species 

 of Psammochares and Aporus, and Adlerz (1902) has succeeded in 

 giving us a complete accoimt of the behavior of C. maculata as he 

 observed it in Sweden. This behavior is so interesting, especially 

 in connection with Graenicher's observations on the parasitic bees, 

 that I subjoin a translation of the German resume of the paper: 



" Ccropalcs has the habit of visiting the breeding grounds of Pompilus 

 species and there alights on small eminences of the soil in order to spy on the 

 Pompilids while they are dragging in. their paralyzed spiders. The tense atti- 

 tude of the wasp, her deflected antennae and her movements as she turns 

 towards a Pompilid that has just come within the range of her vision, are 

 indicative of her keen interest. As Perez and Ferton have observed, the 

 Ccropalcs either alights on the spider while it is being borne along by the 

 Pompilus, unobserved by the latter, or on a spider that is lying unguarded 

 in the open or concealed above the ground, while its captor is busy digging 

 her nest. In either case the Ccropalcs can be seen bending the tip of her 

 abdomen under the spider for the evident purpose of ovipositing. Ferton 

 saw a Ccropalcs cribrata follow a Pouipilus chalybeatus into her burrow 

 while she was dragging in a spider, but although a Ccropalcs larva was 

 afterwards found on the prey, it is not certain that the egg was laid on this 

 occasion. As will be seen from what follows, it might have been laid pre- 

 viously. The only time I saw a Ccropalcs enter a Pompilus burrow was 

 when a P. niger was still busy excavating. No spider was therefore on hand 

 and, of course, oviposition could not have occurred. It was merely a sign of 

 impatience on the part of the parasite, which, after persistently watching the 

 digger, stole down into the burrow as if to inspect the progress of the work. 

 I was present also on a second exceptional occasion when a Ccropalcs 

 pounced down with such violence on a P. cinctellus with its spider that the 

 two wasps and the spider tumbled about together. The little P. cinctellus 

 was so dismayed that she flew away in great haste and never returned. On 

 this occasion the egg which the Ccropalcs probably laid during her subse- 

 quent tedious manipulation of the spider must have perished, because the 

 spider was left in the open where it was exposed to ants and other predatory 



PROC. AMER. PHIL. SOC. VOL. LVIII, B, JUNE II, I919. 



