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LIFE HISTORY OF THE DIGGER-WASP, MELLINUS ARVEN SIS, LINN. BY
HENRY J.
BOREHAM.
THE following account is of the observations carried out by me on the life and habits of this species of Digger Wasp during the months of August to October, 1950 in a man-made sand-hill at Bury St. Edmunds. T H E D I G G I N G AND EXCAVATION OF N E S T HOLE.—The digging and excavating of the nest is the work of each individual $ wasp. There are no communities and no assistance is given by The method of these solitary workers, in digging out the sand, is to use the mouth as a pick and shovel to carry sand to the entrance ; in doing this they always move backwards so that the tail appears first, the markings at the tip of the tail appearing to the observer as those of a face, if the same is slightly inclined upward from the level around the entrance ; the wasp comes out for about an inch (this being about twice its length) before depositing the sand ; it then returns to the face of the tunnel for more sand. After these fetch and carry movements have been repeated four or five times a small heap of sand has accumulated (this small heap is hardly discernible to one's naked eye) ; this is then kicked further back from the entrance of the nest hole by the wasp using its hind pair of feet, which process is repeated after every four or five mouthfuls have been deposited. When the nest is being excavated from the perpendicular side of a sand-bank, the sand is dug and carried in the same way as has already been described, but the methods of disposing it are not the same. In this case the sand is deposited inside the tunnel, the wasp dropping it from its mouth when the tip of its tail touches the outside edge of the entrance hole. Again, after four or five mouthfuls of sand have been deposited and a small heap raised, the wasp does not dispose of it by kicking it further back as in the other method, but pushes it out by using its abdomenal apex ; the sand then falls clear of the workings. All the excavating is done at night and during dull and damp weather, the exception to which is at the commencement of digging when it is carried out in bright and hot sunshine until a certain depth is attained. I have not been able to trace a complete set of the workings, on account of the sand collapsing at the slightest touch.
The following description is of one of those parts of the workings which I have been able to trace, the sand being damp and firmer. The entrances to most of the main tunnels are short and level,