40 PHIL RAU AND NELLIE RAU 



odor when handled. This is not acquired from the environment, 

 but seems to be inherent, for when one cuts open a cocoon 

 containing a full-grown insect, the scent greets one. Whether 

 this scent may be protective we do not know, but we have ob- 

 served that the dead insects are very attractive to mice. On 

 one occasion when I left nine Polistes annularis and P. pallides 

 and seven Osmia pinned to a sheet of cork over night, I found 

 the next morning that the Osmia were neatly nibbled from the 

 pins and no crumb of wings or legs remained, while the Polistes 

 were untouched. Many of these O. cordata pupal cases gave 

 forth Hymenopterous parasites, May 18 to 20, which were 

 identified by Mr. J. C. Crawford as Monodontomerus monti- 

 vagus Ashm. 



On September 16, 1915, in an abandoned log-cabin near 

 Eureka, Mo., we took a number of mud nests which at once 

 appeared interesting because the openings of exit had been 

 resealed with mud. We thought they were the nests of 

 Trypoxylon clavatum or possibly a species of Eumenidae, but 

 upon opening the cells at home we found most of the wasps' 

 cells partitioned with mud and containing from two to four little 

 rooms each. In each compartment I found a pupal case identical 

 in appearance with that of Osmia cordata, but cordata partitions 

 the old cells with a waxy substance, while in all of these the 

 partitions were of mud. I cut open several of the cocoons 

 and found a living adult in each. Here again this species differs 

 from 0. cordata, since the latter appear as adults in the cocoon 

 in early spring. These new bees were larger than cordata and 

 the characteristic sweetish odor was lacking. Most of the cells 

 were heavily parasitized by a Hymenopterous species and were 

 in the pupal stage. 



The specimens were sent to Mr. J. C. Crawford and identified 

 by him as Osmia lignaria Say. Fig. 17 shows the nest of the 

 mud-dauber, with 0. lignaria's two mud partitions, and the 

 mud plug in the old opening. 



We find a note on this species by Packard (in his Guide to 

 the Study of Insects, p. 139, 1889): "The ? of Osmia lignaria 

 Say MS., according to Harris' MS. notes was found in the 

 perfect state in cocoons within earthen cells under stones, April 

 15. The cell she constructs is one-half inch long, oval cylindrical, 

 and contracted slightly into a sort of neck just before the open- 



