The origin of these knotted excrescences completely deceived me at first.

I suspected some cryptogamic vegetation, some _Spheriaecaea_, for example, recognisable by its black, knotted, incrusted growth.

It was the larva that showed me my mistake.
The larva is a maggot curved like a hook, carrying on its back an ample pouch or hunch, forming part of its alimentary canal.

The reserve of excreta in this hunch enables it to seal accidental perforations of the shell of its lodging with an instantaneous jet of mortar.

These sudden emissions, like little worm-casts, are also practised by the Scarabaeus, but the latter rarely makes use of them.
The larvae of the various dung-beetles utilise their alimentary residues in rough-casting their houses, which by their dimensions lend themselves to this method of disposal, while evading the necessity of opening temporary windows by which the ordure can be expelled.