The genus Sitaris, which is allied to the blister-fly and to the oil-beetle, is parasitic on a kind of solitary bee which excavates subterranean galleries, each leading to a cell.  The eggs of the beetle, which are deposited at the entrance of the galleries made by the bees, are hatched at the end of September or beginning of October, and we might not unnaturally expect that the young larvae, which are active little creatures with six serviceable legs, would at once eat their way into the cells of the bee.  No such thing:  till the month of April following they remain without leaving their birthplace, and consequently without food; nor do they in this long time change either in form or size.  M. Fabre ascertained this, not only by examining the burrow of the bees, but also by direct observations of some young larvae kept in captivity.  In April, however, his captives at last awoke from their long lethargy, and hurried anxiously about their prisons.  Naturally inferring that they were in search of food, M. Fabre supposed that this would consist either of the larvae or pupae of the bee, or of the honey with which it stores its cell.  All three were tried without success.  The first two were neglected; and the larvae, when placed on the latter, either hurried away or perished in the attempt, being evidently unable to deal with the sticky substance.  M. Fabre was in despair.  The first ray of light came to him from our countryman Newport, who ascertained that a small parasite found on one of the wild bees was, in fact, the larva of the oil-beetle.  The larvae of Sitaris much resembled this larva.  Acting on this hint, M. Fabre examined many specimens of the bee, and found on them at last the larvae of his Sitaris.  The males of the bee emerge from the pupae sooner than the females, and M. Fabre ascertained that, as they come out of their galleries, the little Sitaris larvae fasten upon them.  Not, however, for long:  instinct teaches them that they are not yet in the straight path of development; and, watching their opportunity, they pass from the male to the female bee.  Guided by these indications, M. Fabre examined several cells of the bee; in some, the egg of the bee floated by itself on the surface of the honey; in others, on the egg, as on a raft, sat the still more minute larva of the Sitaris.  The mystery was solved.  At the moment when the egg is laid, the Sitaris larva springs upon it.  Even while the poor mother is carefully fastening up her cell, her mortal enemy is beginning to devour her offspring; for the egg of the bee serves not only as a raft, but as a repast.  The honey, which is enough for either, would be too little for both; and the Sitaris, therefore, at its first meal, relieves itself from its only rival.  After eight days the egg is consumed, and on the empty shell the Sitaris undergoes its first transformation, and makes its appearance in a very different form.