To make much out of nothing, to fill three starveling bellies, sometimes four, with a single [[27]]crumb, would be out of the question. The secret of the food-supply is not contained in the small amount of solid matter that has disappeared. Let us look into this more closely.
I take out a few larvæ which are already fairly well-grown and install dwellings and dwellers in glass tubes. For a long time, with my pocket-lens, I watch the prisoners. I cannot see that they bite into the central knob, which is already damaged, nor the axis, which also has been cut into. From these surfaces, which have been scored since I know not how long; from what appeared to be their daily bread, their mandibles remove not the smallest particle. At most the mouth is applied for a moment to the surface; then it is withdrawn, uneasy and disdainful. It is evident that the ligneous fare, though still quite fresh, does not suit.
The proof is completed by the final result of my experiments. In vain I keep the thistle-heads fresh in glass tubes, plugged with a stopper of wet cotton-wool: my attempts at rearing are not once crowned with success. As soon as the head is removed from the plant, its inhabitants begin to die of starvation, whether I intervene or whether I do not. They all pine away in the heart of their native globe and at last perish, no matter in what receptacle—test-tube, flask or tin box—I place my collection. Later, on the other hand, when the feeding-period is over, I shall find it very easy [[28]]to keep the grubs in good condition and to follow at will their preparations for the nymphosis.
This failure tells me that the larva of the Spotted Larinus does not sustain itself with solid food; it prefers the clear broth of the sap. It taps the cask of its azure cellar, that is to say, it makes a careful gash in the axis of the head as well as in the central nucleus.
From these surface wounds, which are kept open by fresh strokes of the plane as soon as a dry scab forms upon them, it laps the sap of the thistle, which oozes up from the roots. As long as the blue globe is on its stalk, very much alive, the sap ascends, the broached casks exude their contents and the grub sips the nourishing draught. But, once detached from the stem, cut off from its source of supply, the cellar runs dry. Thereupon the larva promptly dies. This explains the fatal catastrophe of my attempts to rear it.
All that the Larinus-larvæ need is to lick the exudations from a wound. The method employed is henceforth obvious. The new-born grubs, hatched upon the central globe, take their places around its axis, proportioning the distance between them to the number of guests. Each of them peels and slashes with its mandibles the part in front of it, causing the nutritious moisture to exude. If the spring dries up through healing, fresh bites revive it.
But the attack is made with circumspection, [[29]]The central column and its circular capital form the mainstay of the globe. If too extensively injured, the scaffolding would bend before the wind and bring down the dwelling. Moreover, the conduits of the aqueduct must be respected, if a suitable supply of sap is to be provided until the end. Accordingly, whether three or four in number, the grubs abstain from rasping the surface too deeply.
The cuts, which amount to no more than a judicious paring of the surface, imperil neither the solidity of the structure nor the action of the vessels, so that the blossoms, their plunderers notwithstanding, retain a very healthy appearance. They expand as usual, except that the pretty, blue ground is stained with yellow patches, which grow wider from day to day. At each of these points, a grub is established under the cover of the dead florets. Each blemish marks one diner’s seat at table.
The florets, as we said, have for their common support, for their receptacle, the round knob surmounting the axis. It is on this globule that the grubs begin. They attack a few of the florets at their base, uprooting them without injuring them and thrusting them upwards with a heave of the back. The spot thus cleared is slightly broken into and hollowed out and becomes the first refreshment-bar.
What becomes of the items removed? Are [[30]]they thrown to the ground as inconvenient rubbish? The tiny creature is careful not to do anything of the kind, which would mean exposing its plump back, a small but enticing morsel, to the eyes of the foe.