It would be reasonable to suppose that an Insect that takes the pains to provide for the safety of its progeny by constructing a complex edifice of cement, secures thereby the advantage of protection for its young. But this is far from being the case. Notwithstanding the cement and the thick dome of mortar, the _Chalicodoma_ is extremely subject to the attacks of parasites. The work performed by the creature in constructing its mass of masonry is truly astounding; Fabre calculated from measurements he made that for the construction and provisioning of a single cell, the goings and comings of the bee amounted to 15 kilometres, and it makes for each nest sometimes as many as fifteen cells. Notwithstanding all this labour, it would appear that no real safety for the larvae is obtained by the work. Some sixteen—possibly more—other species of Insects get their living off this industrious creature. Another bee, _Stelis nasuta_, breaks open the cells after they have been completely closed and places its own eggs in them, and then again closes the cells with mortar. The larvae of this _Stelis_ develop more rapidly than do those of the _Chalicodoma_, so that the result of this shameless proceeding is that the young one of the legitimate proprietor—as we human beings think it—is starved to death, or is possibly eaten up as a dessert by the _Stelis_ larvae, after they have appropriated all the pudding. Another bee, _Dioxys cincta_, is even more audacious; it flies about in a careless manner among the _Chalicodoma_ at their {44}work, and they do not seem to object to its presence unless it interferes with them in too unmannerly a fashion, when they brush it aside. The _Dioxys_, when the proprietor leaves the cell, will enter it and taste the contents; after having taken a few mouthfuls the impudent creature then deposits an egg in the cell, and, it is pretty certain, places it at or near the bottom of the mass of pollen, so that it is not conspicuously evident to the _Chalicodoma_ when the bee again returns to add to or complete the stock of provisions. Afterwards the constructor deposits its own egg in the cell and closes it. The final result is much the same as in the case of the _Stelis_, that is to say, the _Chalicodoma_ has provided food for an usurper; but it appears probable that the consummation is reached in a somewhat different manner, namely, by the _Dioxys_ larva eating the egg of the _Chalicodoma_, instead of slaughtering the larva. Two of the Hymenoptera Parasitica are very destructive to the _Chalicodoma_, viz. _Leucospis gigas_ and _Monodontomerus nitidus_; the habits of which we have already discussed (vol. v. p. 543) under Chalcididae. Lampert has given a list of the Insects attacking the mason-bee or found in its nests; altogether it would appear that about sixteen species have been recognised, most of which destroy the bee larva, though some possibly destroy the bee's