THE BIOLOGY OF THE MUD-DAUBING WASPS 41 



ing for the exit of the bee. From Mr. James Angus I have 

 received the pellets of pollen, about the size of a pea in which 

 it deposits its egg. The larvae were one-third grown in August." 



This may indicate that the habits of the species have changed 

 within a comparatively short period, and that now she has 

 learned to repair old domiciles instead of building new ones. 



Another insect which makes good use of the empty cells of 

 old nests, as well as holes in fence-posts, etc., is the small 

 Trypoxylon davatum Smith. 15 This wasp uses the old cells in 

 much the same way as does Osmia, but uses mud instead of wax 

 for partition and sealing material. When this species takes 

 possession of the old cells of C. caeruleum and 5. caementarium, 

 she uses them without alteration other than the partitions which 

 she throws in, and the closure of mud. Fig. 25 shows these 

 partitions and the mud plug with contents of the cells removed, 

 while fig. 24 shows in situ the pupal cases amid the remnants 

 of spiders' legs. But when she uses the old empty cocoons of 

 T. albitarsis, she smoothly lines the old pupal case with fine 

 mud and plasters the opening of the cocoon (which is usually 

 flush with the opening in the mud walls), in the same way. 

 Fig. 19 shows a series of old pupal cases of T. albitarsis as used 

 by T. davatum. Figs. a. c and d show the deserted cocoons of 

 T. albitarsis with the exits plastered over or the interior lined 

 with mud. These plugs of mud have in turn been pierced by 

 the emerging T. davatum. Fig. b (and also fig. 16) are the 

 cocoons of T. davatum, natural size. The material in this is 

 the same as that of the T. albitarsis cocoons, but it is thinner. 

 Since it is itself enclosed in the heavy cocoon of T. albitarsis 

 it need not be heavier or stronger. Figs, e and / show sections 

 of the resealed cocoons; fig. g is the mud plug removed from a 

 cell to show the neat hole made by the escaping T. davatum, 

 and fig. h shows the interior of a nest of T. davatum where the 

 larva is snug and thriving in the old pupal shell of T. albitarsis. 



One often finds that the mother T. davatum, before storing 

 the spiders for her young in an old cell has had a thorough 

 house-cleaning, but instead of brushing the rubbish, spiders 

 legs, Anthrenus shedding skins, etc., out through the doorway 

 she has swept them into the corner, as far back as possible, 

 and walled them up with a partition of mud. This is poor 

 15 Kindly identified by Mr. S. A. Rohwer. 



