As for the one nail, this is explained by the tarsi, the insect’s six fingers, each of which is armed with a single claw instead of the usual two. This strange exception certainly deserved to be pointed out; all the same, any one must prefer Iris-weevil to Mononychus pseudo-acori. Neglecting all pomp and ostentation, the everyday name does not topsy-turvify the mind and makes straight for the insect.
In June, I pluck some stems of yellow iris surmounted by their bunch of capsules, which are [[238]]already large and keep fresh and green for a long time. The exploiting Weevil goes with them. In captivity, under the trellis-work of a wire-gauze cover, the work proceeds just as it does beside the brook. Most of the insects, singly or in groups, stand at convenient points. With their rostrum plunged into the green hull, they sip and sup indefinitely. When they retire sated, a drop of gum oozes out which, after drying on the orifice of the well, marks the spot which they have drained.
Others are grazing. They attack the tender capsules and skin them almost down to the seeds. Despite their tiny size, they nibble gluttonously; when several of them are feasting together, they gnaw large areas; but they do not actually reach the seeds, the food reserved for the larvæ. Many of them stroll about, seem not to care for eating. They meet, tease one another for a moment and couple.
I do not succeed in observing the method of laying, which, however, must be much the same as that of the other Weevils who use a sound. The mother apparently bores a well with her rostrum; she then turns and places the egg in position by means of her oviscapt. I have seen larvæ quite recently hatched. The vermin occupy the interior of a seed whose substance is becoming organized and beginning to grow firm.
At the end of July, I open some capsules brought [[239]]on the same day from the banks of the stream. In most of them the insect occurs in the three forms of larva, nymph and adult. Each of the three cells of the fruit contains a row of some fifteen seeds, flat and pressed tightly one against the other. The grub’s portion consists of three contiguous seeds. The one in the middle is entirely consumed, excepting the husk, which is too tough; the two at either end are simply bitten into. The result is a house with three rooms, the central one shaped like a ring, the two outer ones dug cup-wise.
With its fifteen seeds, each compartment of the fruit is therefore able to shelter five larvæ at most, providing them with a fitting ration and a detached villa which does not interfere with the neighbours. However, on the back of the capsule, we count, for each cell, about twenty perforations, the edge of which is marked by a little wart either of gum or of some brown substance. These are so many soundings made by the Weevil’s rostrum.
Some of these have to do with the feeding: they are the refreshment-bars at which the colonists of the capsule have taken a snack. The others relate to the laying of the eggs and the placing of them, one by one, in the midst of the victuals. Outwardly there is nothing to distinguish the speck which marks a refreshment-bar from that which marks a cradle; therefore it is impossible, by merely counting the borings, to tell exactly how [[240]]many eggs have been confided to the capsule. Let us strike an average. Of the twenty punctures in one shell, let us consider ten as relating to the eggs. These would be twice as many as the cell could feed. What then has become of the surplus?
Here we are reminded of the Weevil who scatters over her pea-pod an excessive number of eggs, out of all proportion to the provisions which it contains. In the same way, on the iris, the pregnant mother takes no stock of the rations; she peoples the already populated and fills the overflowing. Her procreative fury does not reckon with the future. Let those thrive who may.
We can understand Verbascum thapsus allowing itself forty-eight thousand seeds when the germination of a single one would suffice to maintain the species: its distaff is a treasure-house of food by which a host of consumers will profit. But we cannot understand the Pea-weevil, the Iris-weevil and many others who, though not exposed to a serious thinning, nevertheless produce excessive families without taking into account the resources at their disposal.
For lack of room on the seed-capsule of the iris, of the ten guests in one shell four or five at most will survive. As for the disappearance of the rest, we need not seek the cause in the massacring of rivals, though the struggle for existence is fruitful in such crimes. The Weevil’s grub is too pacific [[241]]a creature to wring the neck of those which get in its way. I prefer the explanation which I gave in the case of the Pea-weevil. The late-comers, finding the best places taken, allow themselves to die without striving to dislodge the others. For those first installed, a plentiful board and life; for those which lag behind, famine and death.