540 HYMENOPTERA 



and Aphididae, and some deposit their eggs in the egg-cases of 

 Blattidae. The details of the life-history are well known in 

 only a few cases. 



The career of Leucospis gigas has been investigated by Fabre, 

 and exhibits a very remarkable form of hypermetamorphosis.^ 



This Insect is of comparatively 

 large size and of vivid colours, 

 wasp-like, black contrasting with 

 yellow, as in the case of the 

 wasps ; and like these it has the 

 wings folded or doubled. The 

 female bears a long ovipositor, 

 which by a peculiar modification 

 Fig. i5&.— Leucospis gigas, female. is packed in a groovc on the 



back of the Insect. This species 



lives in Southern Europe at the expense of Chalicocloma muraria, 



a mason-bee that forms cells of a hard cement for its nest, the 



cells being placed together in masses of considerable size ; each cell 



contains, or rather should contain, a larva of the bee, and is closed 



by masonry, in the construction of which the bee displays much 



ability. It is the mission of the Leucospis to penetrate the 



masonry by means of its ovipositor, and to deposit an egg in the 



cell of the bee. The period chosen for this predatory attack is 



the end of July or the beginning of August, at which time the 



bee-larva is in the torpid and powerless condition that precedes 



its assumption of the pupal state. The Leucospis, walking about 



leisurely and circumspectly on the masonry of the nest, tests it 



repeatedly by touching with the tips of the antennae, for it is 



most important that a proper spot should be selected. The bee's 



cell is placed in a mass of solid masonry, a considerable part — 



but a part only — of whose area is occupied by the group of cells ; 



every cell is closed by hard mortar, making an uneven surface, 



and the face of the masonry is rendered more even by a layer of 



hardened clay outside the rougher material ; it is the task of the 



Leucospis to detect a suitable spot, in the apparently uniform 



external covering, and there to effect the penetration so as to 



introduce an egg into a cell. By what sensations the fiy may 



be guided is unknown. After a spot has been selected and the 



ovipositor brought into play, the masonry is ultimately pierced 



' Souvenirs entomologiqucs. Troisieme serie, 1886, p. 155. 



