A second point becomes clear. In order to insert the egg at convenient points, it is the rule for the insect to possess an implement with two functions, an implement which at the same time opens the passage and guides the eggs along it. [[24]]This is the case with the Cicada,[1] the Grasshopper,[2] the Saw-fly, the Leucospis[3] and the Ichneumon-fly,[4] all of whom carry a sabre, a saw or a probe at the tip of the abdomen.
The Weevil divides the work and apportions it between two implements, one of which, in front, is the perforating auger, and the other, behind, hidden in the body and unsheathed at the moment of the laying, is the guiding tube. Except in the Weevils, this curious mechanism is unknown to me.
When the egg is placed in position—and this is quickly done, thanks to the preliminary work of the drill—the mother returns to the point colonized. She packs the disturbed materials a little, she lightly pushes back the uprooted florets; then, without taking further trouble, she goes away. She sometimes even dispenses with these precautions.
A few hours later, I examine the heads exploited, which may be recognized by a certain number of faded and slightly projecting patches, each of which shelters an egg. With the point of my penknife I extract the little, faded bundle and open it. At the base, in a small round cell, hollowed [[25]]out of the substance of the central globule, the receptacle of the thistle-head, is the egg, fairly large, yellow and oval.
It is enveloped in a brown substance derived from the tissues injured by the mother’s auger and from the exudations of the wound, which have set like cement. This envelope rises into an irregular cone and ends in the withered florets. In the centre of the tuft we generally see an opening, which might well be a ventilating-shaft.
The number of eggs entrusted to a single head may easily be ascertained without destroying the cells: all that we need do is to count the yellow blurs unevenly distributed over the blue background. I have found five, six and more, even in a head smaller than a cherry. Each covers an egg. Do all these eggs come from the same mother? It is possible. At the same time, they may be of diverse origin, for it is not unusual to surprise two mothers both occupied in laying eggs on the same globe.
Sometimes the points worked upon almost touch. The mother, it seems, has a very restricted numerical sense and is incapable of keeping count of the occupants. She drives her probe into the florets, unheeding that the place beside her is already taken. As a rule there are too many, far too many feasters at the niggardly banquet of the blue thistle. Three at most will find enough to live on. The first-comers will thrive; the [[26]]laggards will perish for lack of room at the common table.
The grubs are hatched in a week: little white atoms with red heads to them. Suppose them to be three in number, as frequently happens. What have the little creatures in their larder? Next to nothing. The echinops is an exception among the Carduaceæ. Its flowers do not rest upon a fleshy receptacle expanded into a heart, like the artichoke’s. Let us open one of the heads. In the centre, as a common support, is a round firm nucleus, a globe hardly as large as a peppercorn, fixed on the top of a little column which is a continuation of the axis of the stem. That is all.
A scanty, a very scanty provision for three consumers. In bulk there is not enough to furnish the first few meals of a single grub; still less is there enough—for it is very tough and unsubstantial—to provide for those fine layers of fat which make the grub look as sleek as butter and are employed as reserves during the transformation.
Nevertheless, it is in this paltry globule and the small column which supports it that the three boarders find, their whole life long, the wherewithal to feed and grow. Not a bite is given elsewhere; and even so the attack is delivered with extreme discretion. The food is rasped and nibbled on the surface and not completely consumed.