264 THE FOSSORIA. 



many as fifty or sixty Aphides are sometimes impri- 

 soned together in a single nest. 



From the almost constant habit of burrowing dis- 

 played by these insects, the tribe which they form 

 has been denominated that of the FOSSORIA, or Dig- 

 ging Hymenoptera, and the large number which 

 carry on their mining operations in sandy ground are 

 commonly known as Sand-wasps. They are distin- 

 guished from the Ants by their having only two 

 sexes, males and perfect females; and by the con- 

 stant occurrence of wings in the latter sex, although 

 this character is not without exceptions, the females 

 of the genus Mutilla and its allies being always 

 apterous, from which circumstance those insects have 

 been placed by many authors amongst the Hetero- 

 gyna ; the absence of the scale on the petiole of the 

 abdomen will, however, serve to distinguish them. 

 From the succeeding groups of Aculeate Hymeno- 

 ptera they are distinguished by the absence of an 

 elongated or thread-like tongue, by their flat wings 

 lying straight upon the back during repose, and by 

 the want of any arrangement of the legs, to enable 

 them to carry the pollen of flowers to their nests. 

 On the other hand, the legs are for the most part 

 furnished with spines to assist them in their burrow- 

 ing operations. A good many species, however, do 

 not trouble themselves with making a burrow and 

 collecting the necessary supplies, but taking advan- 

 tage of the labours of their more industrious neigh- 

 bours, slip into their nests during their absence and 

 leave behind them an egg, the larva hatched from 

 which lives parasitically at the expense of the rightful 

 owner. 



