Fabre has made us acquainted with some points in the history of another species of the same genus, viz. _Stelis nasuta_, that show a decided departure from the habits of _S. minuta_. The first-named Insect accomplishes the very difficult task of breaking open the cells of the mason-bee, _Chalicodoma muraria_, after they have been sealed up, and then, being an Insect of much smaller size than the _Chalicodoma_, places several eggs in one cell of that bee. Friese informs us that parasitic bees and their hosts, in a great number of cases, not only have in the perfect state the tongue similarly formed, but also frequent the same species of flower; thus _Colletes daviesanus_ and its parasite _Epeolus variegatus_ both specially affect the flowers of _Tanacetum vulgare_. Some of the parasitic bees have a great resemblance to their hosts; _Stelis signata_, for instance, is said to be so like _Anthidium strigatum_ that for many years it was considered to be a species of the genus _Anthidium_. In other cases not the least resemblance exists between the parasites and hosts. Thus the species of _Nomada_ that live at the expense of species of the genus _Andrena_ have no resemblance thereto. Friese further tells us that the _Andrena_ and _Nomada_ are on the most friendly terms. _Andrena_, as is well known, forms populous colonies in banks, paths, etc., and in these colonies the destroying _Nomada_ flies about unmolested; indeed, according to Friese, it is treated as a welcome guest. He says he has often seen, and in several localities, _Nomada lathburiana_ and _Andrena ovina_ flying peacefully together. The _Nomada_ would enter a burrow, and if it found the _Andrena_ therein, would come out and try another burrow; if when a marauding _Nomada_ was in a burrow, and the rightful owner, returning laden with pollen, found on entering its home that an uninvited guest was therein, the _Andrena_ would go out in order to permit the exit of the _Nomada_, and then would again enter and add the pollen to the store. Strange as this may seem at first sight, it is really not so, for, as we have before had occasion to observe, there is not the slightest reason for believing that host Insects have any idea whatever that the parasites or inquilines are injurious to their {31}race. Why then should they attack the creatures? Provided the parasites do not interfere in any unmannerly way with the hosts and their work, there is no reason why the latter should resent their presence. The wild bee that seals up its cell when it has laid an egg therein, and then leaves it for ever, has no conception of the form of its progeny; never in the history of the race of the _Andrena_ has a larva seen a perfect insect and survived thereafter, never has a perfect Insect seen a larva. There is no reason whatever for believing that these Insects have the least conception of their own metamorphosis, and how then should they have any idea of the metamorphosis of the parasite? If the