298 HYMENOPTERA 



Sceliphron cells, but they are probably indirect parasites, 

 their larvae feeding upon the spiders and not upon the 

 Sceliphron larvae, which thus die of hunger. 



A smaller species of Sceliphron makes cells somewhat 

 similar to the mud nests built by S. spirifex, but they 

 are placed upon grass stems and are of more delicate 

 structure, being composed of some light friable material 

 mixed with fibrous substance. These nests were common 

 also on Kerenge Isle, and were filled with spiders. 



The great majority of Sphegidae, however, are true 

 fossors — that is, they excavate burrows into which the 

 paralysed prey is put. 



Since a Sphegid having once stocked the burrow pays 

 no more attention to it, there is no need for it to work 

 like Bembex in loose light soil ; indeed, the firmer it is 

 the better they seem to like it, and often may be seen 

 working on the hard surface of a trodden pathway. 



The methods of a Sphegid differ somewhat from those 

 of a Bembex. The earth cannot be removed by mere 

 scratching, but needs to be excavated by " tooth and 

 nail." 



An Ammophila, for instance, having found a suitable 

 site, commences to scrape together a little of the loose 

 soil on top, which she holds between her front feet and 

 head and, having walked backwards a few inches, deposits 

 it with a little buzz of satisfaction and returns for another 

 armful. Presently the soil is found firmer, and she sets 

 to work with her powerful mandibles to loosen it, some- 

 times bringing up portions in her jaws. The work pro- 

 ceeds with rapidity until the hole descends vertically to 

 such a depth that she disappears from view. 



She seems to be on springs, so full of life and energy 

 is she ; it is often extremely curious to note how rapidly 

 she shoots out from the burrow backwards, drops her 

 load, and plunges headlong down the hole again as if 

 drawn by a piece of elastic attached to the bottom thereof. 



