134 



THE AMERICAN ENTOMOLOGIST. 



two kinds of L'ocoon b3 promiscuously inter- 

 mixed? Wliy should both kinds of larv.-e be 

 led upon spiders? Why should th? claj'-cell, in 

 which the Black Wasp rears its young, be so 

 manifestly the work of the Mud-dauber, that no 

 difforenco whatever can be perceived between 

 those tenanted by the two dilferent kinds of 

 cocoon, save the clay partition in the middle, 

 usually found, when the cell contains tlio co- 

 coons of the Black Wasp, but never found 

 when it contains the cocoon of the Mud-dauber? 

 Most naturalists are tolerably well satisfied willi 

 evidence as strong as this; and for many years 

 it staggered and puzzled us. 



In the spring of 1867, we determined, if pos- 

 sible, to solve the enigma. We procured a very 

 large quantity of the "Mud-dabs," containing 

 both kinds of cocoons, and examined them at 

 home, at our leisure. Thus we arrived at the 

 ibllowing results, each of which will be accom- 

 panied by the proofs that establish it. 



1st. The 3Tud-dauber, as xvell as the Black 

 Ifusp, must often make use of the old last year's 

 mud-cells constructed by the former.— \n two 

 "mud-dabs" where there was a double tier of 

 cells— the outer one of course not built ])io- 

 viously to the inner one, for the simple reason 

 that the inner one formed th:; foundation-wall 

 for it— we found on March 9th, 18(;7, in the outer 

 tier, dead and dry Digger Arasji^ in tlio perfect 

 or winged state. Hence it )oll(.i\\ < i !ial llir outer 

 tier must have been constructed at least as early 

 as the summer of 1805; for if constructed in the 

 summer of 186G its cells would necessarily, on 

 March 0th, 18G7, have contained larvaj nearly 

 ready to change to pupas, or at all events pup«, 

 and not living winged wasps, and still less dead 

 and dried up wasps. Consequently, the inner 

 tier, having been built before the outer tier as 

 already shown, must also have been constructed 

 at least as early as the summer of 186.5. But 

 that inner tier on March 9th, 1807, contained 

 at least one fresh cocoon of the Mud-dauber, as 

 well as numerous fresh cocoons of the Black 

 Wasp, intermixed together; and therefore both 

 kinds of cocoon must have taken their origin 

 from eggs deposited in the summer of 1866 in 

 old cells which, as has been already proved, 

 were built at least as early as the summer of 

 186-j and perhaps a year or two sooner. Thus, 

 as both the Mud-dauber and the Black Wasp are 

 proved to make use, occasionally at all evcnt.s, 

 of the old last year's cells of the former, the 

 promiscuous occurrence of their cocoons is easily 

 explained. 



2nd. The Black Was}) provisions its nest with 

 different genera of spiders fro7n those used by 



the Mud-Dauber. — It occasionally happens with 

 most Digger Wasps, that the egg fails to hatch 

 out ; or the larva, having hatched out, perishes 

 from unknown causes at an early age. In these 

 cases, therefore, the food stored up for the larva 

 remains uneaten, or mostly uneaten. By dili- 

 gent search, we found two such cells, which 

 had manifestly been provisioned by the Black 

 Wasp, because each formed the inner portion of 

 a full-sized cell, divided in two by the usual 

 partition, and the outer portion of it contained 

 the cocoon ol a Black Wasp. Emptying out 

 into hot water the dead spiders contained in 

 these two cells, which were in a fair state of 

 preservation, and also, a few in tolerably good 

 order, found at the bottom of .some cells tenanted 

 by the cocoons of the Black AVasp, we found 

 them to bo seventeen in number, and all of 

 them to belong to one genus and species, 

 except two, which, apparently, belonged to a 

 different species of the same genus. It re- 

 mained to ascertain wliat species of spiders 

 were u-ed by the Mud-Dauber. For this pur- 

 pose, it evidently would not answer to examine 

 the contents of a cell without any partition in 

 the middle, and in which the egg or young 

 larva had perished prematurely, provided it 

 was found in the same locality as the abore. 

 For, as the Black Wasp occasionally erects no 

 partition-wall in the cell whicii it occupies, 

 there would then have been no certainty which 

 insect of the two had provisioned it with 

 spiders. Consequently, we examined " mud- 

 dabs"' Irom a locality where they are never 

 tenanted by the Black Wasp; and having found 

 several cells in them full of nothing but spiders, 

 from causes already explained, we ascertained 

 tint those spiders, which were thirty in num- 

 ber, apparently belonged to, at least, four 

 different genera, the number of individ- 

 uals belonging to each genus, being respec- 

 tively, 1, 6, 6, and 17; and that they were 

 all, not only specifically, but generically, distinct 

 from those found in the cells tenanted by the 

 Black Wasp. We may add further, that some 

 seven or eight more or less imperfect speci- 

 mens, found in cells occupied by the cocoons of 

 the Mud-Dauber in the first lot of " mud-dabs," 

 all apparently belonged to the genus most 

 numerously represented in the second lot of 

 " mud-dabs.'' 



ord. Other genera of wasps, besides the Black 

 Wasp referred to above, occasionally use the 

 second-hand cells of the Mud-dauber as a nest for 

 theirlarvn;. Inalarge masscontainingnumerous 

 cells, occupied partly by cocoons of the Mud- 

 dauber and partly by those of the Black Wasp, 



