In September, 1828, a common species of solitary mason-wasp (_Odynerus_, Latr.) was observed by us (J. R.) on the east wall of a house at Lee, in Kent, very busy in excavating a hole in one of the bricks, about five feet from the ground. Whether there might not have been an accidental hole in the brick before the wasp commenced her labours, is unknown, as she had made considerable progress in the work when first observed: but the brick was one of the hardest of the yellow sort made in this neighbourhood. The most remarkable circumstance in the process of hewing into the brick was the care of the insect in removing to a distance the fragments which from time to time she succeeded in detaching. It did not appear to suit her design to wear down the brick, particle by particle, as the furniture beetle (_Anobium pertinax_) does in making its pin-hole galleries in old wood. Our wasp-architect, on the contrary, by means of her strong _tranchant_-toothed jaws, severed a piece usually about the bigness of a mustard-seed. It might have been supposed that these fragments would have been tossed out of the hole as the work proceeded, without further concern; as the mole tosses above ground the earth which has been cleared out of its subterranean gallery. The wasp was of a different opinion; for it was possible that a heap of brick chips, at the bottom of the wall, might lead to the discovery of her nest by some of her enemies, particularly by one or other of the numerous tribe of what are called _ichneumon_-flies. This name is given to them, from the similarity of their habit of destroying eggs, to that of the little animal which proves so formidable an enemy to the multiplication of the crocodile of Egypt. They may be also denominated _cuckoo_-flies, because, like that bird, they thrust their egg into the nest of another species. These flies are continually prowling about and prying into every corner, to find, by stealth, a nidus for their eggs. It might have been some such consideration as this which induced the wasp to carry off the fragments as they were successively detached. That concealment was the motive, indeed, was proved: for one of the fragments which fell out of the hole by accident, she immediately sought for at the bottom of the wall, and carried off like the rest. It was no easy matter to get out one of the fragments, as may readily be conceived when the size of the insect is compared with that of the entrance of which this ([Illustration]) is the exact size, as taken from the impression of a bit of dough upon the hole when finished. It was only by seizing the fragment with her jaws, and retreating backwards, that the matter could be accomplished; though, after the interior of the excavation was barely large enough to admit of her turning round, she more than once attempted to make her exit head-foremost, but always unsuccessfully. The weight of the fragments removed did not appear to impede her flight, and she generally returned