What is lacking? Not the ligneous materials, which can always be obtained from the grub’s surroundings, but the adhesive cement, the factory having closed down. And why has it closed down? The answer is quite simple: because the vessels [[33]]of the thistle-head detached from its stalk are dry and can no longer furnish the food upon which everything depends.
The curly-bearded Chaldean used to build with bricks of mud baked in the kiln and cemented with bitumen. The Weevil of the blue thistle possessed the secret of asphalt long before man did. Better still: to put its method into practice with a rapidity and economy unknown to the Babylonian contractors, it had and still has its own well of bitumen.
What can this viscous substance be? As I have explained, it appears in opal drops at the waste-pipe of the intestine. Becoming hard and resinous on contact with the air, it turns a tawny red, so much so that the inside of the cell looks at first as though coated with quince-jelly. The final hue is a dull brown, against which pale specks of mixed ligneous refuse stand out sharply.
The first idea that occurs to one’s mind is that the Weevil’s glue must be some special secretion, not unlike silk, but emerging from the opposite pole. Can there be actually glands secreting a viscous fluid in the grub’s hinder part? I open a larva which is busily building. Things are not as I imagined: there is no glandular apparatus attached to the lower end of the digestive canal.
Nor is there anything to be seen in the ventricle. Only the Malpighian tubes, which are rather large [[34]]and four in number, reveal, by their opaline tint, the fact that they are fairly full; while the lower portion of the intestine is dilated with a pulpy substance which conspicuously attracts the eye.
It is a semi-fluid, viscous, treacly material of a muddy white. I perceive that it contains an abundance of opaque corpuscles, like finely powdered chalk, which effervesce when dissolved in nitric acid and are therefore uric products.
This very soft pulp is, beyond a doubt, the cement which the grub ejects and collects drop by drop; and the rectum is obviously the bitumen-warehouse. The parity of aspect, colour, and treacly consistency are to me decisive: the grub consolidates and cements and creates a work of art with the refuse from its sewer.
Is this really an excremental residue? Doubts may be permitted. The four Malpighian tubes which have poured the powdered urates into the intestine might well supply it with other materials. They do not in general seem to perform very exclusive duties. Why should they not be entrusted with various functions in a poorly-equipped organism? They fill with a chalky broth to enable the Capricorn’s larva to block the doorway of its cell with a marble slab. It would not be at all surprising if they were also gorged with the viscous fluid that becomes the asphalt of the Larinus. [[35]]
In this embarrassing instance the following explanation may possibly suffice. The Larinus’ larva observes, as we know, a very light diet, consisting of sap instead of solid food. Therefore there is no coarse residue. I have never seen any dirt in the cell; its cleanliness is perfect.
This does not mean that all the nourishment is absorbed. There is certainly refuse of no nutritive value, but it is thin and almost fluid. Can this be the pitch that cements and stops up the chinks? Why not? If so, the grub would be building with its excrement; with its ordure it would be making a pretty home.