The attainments of the Curculionid mother are, generally speaking, limited to inserting her eggs at places where the grubs will find suitable nourishment and occasionally varying the diet with a botanical judgment of marvellous certainty. She displays little or no industry. The niceties of the feeding-bottle or the baby-linen do not concern her. To this rough conception of the duties of maternity, I know but one exception, the attribute of certain Weevils, who, in order to endow their young with an alimentary preserve, possess the art of rolling a leaf, which serves as board and lodging in one.
Among these manufacturers of vegetable sausages, the most skilful is the Poplar Weevil (Rhynchites Populi, Lin.), who is modest in proportions, but resplendent in attire. Her back is clad in gleaming gold and copper; her back is indigo blue. Would you see her at work, you need but visit the lower twigs of the common black poplar, at the edge of the meadows, about the end of May.
Whereas, up at the top, the fond spring breezes shake the majestic green distaff and set the leaves quivering on their flattened stalks, down below, in a zone of calmer air, the tender shoots of the year remain quiescent. Here, especially, far from the wind-tossed heights opposed to [[185]]labour, the Rhynchites works. And, as the workshop is just at a man’s height, nothing is more easy than to observe the roller’s actions.
Easy, yes, but distressing, under a blazing sun, if one would follow the insect in all the detail of its methods and the progress of its work. Moreover, this involves a great deal of walking, which takes up time; and, again, it is not favourable to precise observations, which require an indefinite amount of leisure and assiduous visits at all hours of the day. It would, therefore, be greatly preferable to study the animal comfortably at home; but it is above all things necessary that she should lend herself to this plan.
The Rhynchites fulfils the condition excellently well. She is a peaceable enthusiast and works on my table with the same zest as in her poplar-tree. A few tender shoots, planted in fresh sand, under a woven-wire cover, and renewed as soon as they begin to fade, take the place of the tree in my study. The Weevil, not in the least intimidated, devotes herself to her industry even under the lens of my magnifying-glass and supplies me with as many scrolls as I could wish for.
Let us watch her at work. She picks the leaf which she proposes to roll from the young shoots sprouting in sheaves at the base of the trunk, but picks it not among the lower leaves, which are already the correct green and of a firm texture, nor yet among the terminal leaves, which are in a fair way of growing. Above, they are too young, not wide enough; below, they are too old, too tough, too hard to manage.
The leaf selected belongs to the intermediate rows. As yet of a doubtful green, in which yellow predominates, soft and glossy with varnish, it has, or has very nearly, [[186]]the final dimensions. Its denticulations swell into delicate glandular pads, whence oozes a little of the viscous matter that tars the buds at the moment when their bracts become disjoined.
A word now on the equipment in respect of tools. The legs are supplied with double claws shaped like the meat-hooks of a steel-yard. The lower side of the tarsi carries a thick tuft of white bristles. Thus shod, the insect clambers very nimbly up the most slippery vertical walls; it can stand and run like a fly, with its back downwards, on the ceiling of a glass bell. This characteristic alone is enough to suggest the subtle sense of equilibrium which the Weevil’s work will demand.
The curved and powerful beak or rostrum, without being exaggerated in size, spreads at the tip into a spatula ending in a pair of fine, shear-like mandibles. It makes an excellent bodkin, which plays the first or leading part in the whole work. The leaf, in fact, cannot be rolled in its actual condition. It is a live blade which, owing to the afflux of the sap and the tonicity of the tissues, would resume its flat formation in proportion as the insect endeavoured to curve it. The dwarf insect has not the strength to master a piece of these dimensions, to roll it up so long as it retains the elasticity of life. This is evident to our eyes; it is evident also to the eyes of the Weevil.
How is she to obtain the degree of inert suppleness required in the circumstances? We ourselves would say: