134 



THE AMERICAN ENTOMOLOGIST. 



two kinds of cocoon bs promiscuously inter- 

 mixed? Why should both kinds of larvse be 

 fed upon spiders? Why should the clay-cell, in 

 which the Black Wasp rears its young, be so 

 manifestly the work of the Mud-dauber, that no 

 difference whatever can be perceived between 

 those tenanted by the two different kinds of 

 cocoon, save the clay partition in the middle, 

 usually found, when the cell contains the co- 

 coons of the Black Wasp, but never found 

 when it contains the cocoon of the Mud-dauber? 

 Most naturalists are tolerably well satisfied with 

 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 

 following results, each of which will be accom- 

 panied by the proofs that establish it. 



1st. The Mud-dauher, as well as the Black 

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

 mud-cells constructed by the former. — In two 

 "mud-dabs" where thei-e was a double tier of 

 cells— the outer one of course not built pre- 

 viously to the inner one, for the simple reason 

 that the inner one formed the foundation-wall 

 for it— we found on March 9th, 18G7, in the outer 

 tier, dead and dry Digger Wasps in the perfect 

 or winged state. Hence it follows that the outer 

 tier must have been constructed at least as early 

 as the summer of 1865 ; for if constructed in the 

 summer of 1866 its cells would necessarily, on 

 March 9th, 1867, have contained larvas nearly 

 ready to change to piipje, or at all events pupa?, 

 and not living winged wasps, and still less dead 

 and dried up wasps. Consequently, the inner 

 <ier, having been built before the outer tier as 

 already shown, must also have been constructed 

 at least as early as the summer of 1865. But 

 that inner tier on March 9th, 1867, 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 

 1865 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 events, 

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

 promiscuous occurrence of their cocoons is easily 

 explained. 



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

 different genera of spiders from 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 mostlj^ 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 of 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 Wasp, we found 

 them to be seventeen in nurabei', 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 what species of spiders 

 were used by the Mud-Dauber. For this pur- 

 pose, it evidently would not answer to examine 

 the co}itent^ 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 aboce. 

 For, as the Black Wasp occasionally erects no 

 parfitio!i-wall in the cell which it occupies, 

 there would then have been no certainty which 

 insect of (he two had provisioned it with 

 spiders. Consequently, we examined "mud- 

 dabs" from a locality where they are never 

 tenanted by the Black Wasp; and having found 

 several cells in them fnll of nothing but spiders, 

 from causes already explained, we ascertained 

 that these 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, C, 6, and 17; and that they were 

 all, not only specifically, but generically, distinct 

 from those found in the cells tenanted bj'^ the 

 Black Wasp. We may add further, that some 

 seven or eight more or less imperfect speci- 

 inens, found in cells occupied by the cocoons of 

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

 all appai-ently belonged to the genus most 

 numerously represented in tho second lot of 

 " mud-dabs." 



3rd. 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 

 iheirlariw. lualarge mass containing numerous 

 cells, occupied partly by cocoons of the Mud- 

 dauber and partly by (hose of the Black Wasp, 



