1865.] ENTOMOLOGICAL SOCIETY. 463 



<of the structure, therefore, its contents were exposed when it was 

 detached from its position. It contained the larva of the hyme- 

 nopter and two fresh looking caterpillars, which it devoured 

 together with a common fly that I gave it on the following day. 

 The larva is about half an inch long, flesh-colored, smooth and 

 glossy, having about thirteen rings. It has since lined the interior 

 of its nest with a coating of fine white silken threads. It is 

 difficult to explain the use of the button-like form which is always 

 on the top of the nest of this wasp. When I found the nest, it 

 contained two small caterpillars which only served the larva one 

 day, and it afterwards devoured common houseflies. Can it be 

 that the button or top is removed by the parent insect in order to 

 supply its progeny with additional food ? When the architecture 

 of this wasp is newly formed, the top has a regular concavity, and 

 the edges are well rounded and sharp, which is the case with the 

 specimen found on the 25th July. The top of specimens found 

 early in spring, and which were exposed during winter, are not so 

 perfect, and after making allowance for exposure to the weather, I 

 am led to think that the parent insect opens the top of the nest 

 to supply the larva with additional food, reconstructing it with less 

 regularity than the original form : the top is evidently the last part 

 of the structure finished. There is no other substance but clay 

 or mud and sand used by the parent insect, and it is not until the 

 larva had finished feeding, and devours the material supplied to it, 

 that it lines the walls of its cell. The economy of this insect is 

 not yet thoroughly investigated. I may have another opportunity 

 of doing so. 



Fig. 2. — The three nests above figured were found attached to 

 the bark of a stump in the same locality where the former speci- 

 men was found. They belong to a different genus, and the archi- 

 tecture corresponds with that of the genus Osmia, an European 

 mason-bee, the cells of which are figured in Rennie's Insect 

 Architecture, p. 41, fig. 2. The nests of this insect are made of 

 clay and sand, but they are smaller than those of Osmia bicornis 

 of Europe. There are three series of cells illustrated in this 

 work, two of which produced the last-named insect, and 

 from the third came MegachUe muraria, and a dipterous 

 parasite. The author is evidently at fault, as the simi- 

 larity of structure represented by the illustrations are alone 

 sufficient to show the work of one species. M. muraria Linn., is a 

 sand-burrowing bee, and I am not aware that it is a parasite on 



