220 INSECTS. 



shells forming the roof of a Wasp's nest, lately found in 

 the roof of a dwelling-house, were beautified with zones 

 of green, the little architects having made use of decayed 

 wood coloured by the spores of P. seruginosa. 



The species of Solitary Wasps are not always very 

 easily distinguished, and would require a more minute 

 description than space will allow to be given here. The 

 females and workers of the Ground and Tree-wasps 

 may, however, be distinguished by the colour of the 

 first joint of the antennae. In the former (Ground- 

 wasps, i.e., V. vulgaris, PL VIII., fig. 5, 5a, V. Ger- 

 manica, ru/a) this is black, and in the latter (Tree- 

 wasps, i.e,, V. arborea, sylvestris, Norvegica, PL VIII., 

 fig. 6, 6a, and V. Crabro) it is yellow in front, as in the 

 males of all the species. 



