There is perhaps no surer criterion of reason than, after having tried one mode of accomplishing a purpose, adopting another more likely to succeed. Insects are able to stand this test. A bee which Huber watched while soldering the angles of a cell with propolis, detached a thread of this material with which she entered the cell. Instinct would have taught her to separate it of the exact length required; but after applying it to the angle of the cell, she found it too long, and cut off a portion so as to fit it to her purpose[813].
This is a very simple instance; but one such fact is as decisive in proof of reason as a thousand more complex, and of such there is no lack. Dr. Darwin (whose authority in the present case depending not on hearsay, but his own observation, may be here taken,) informs us, that walking one day in his garden he perceived a wasp upon the gravel walk with a large fly nearly as big as itself which it had caught. Kneeling down he distinctly saw it cut off the head and abdomen, and then taking up with its feet the trunk or middle portion of the body to which the wings remained attached, fly away. But a breeze of wind acting upon the wings of the fly turned round the wasp with its burthen, and impeded its progress. Upon this it alighted again on the gravel walk, deliberately sawed off first one wing and then the other; and having thus removed the cause of its embarrassment, flew off with its booty[814]. Could any process of ratiocination be more perfect? "Something acts upon the wings of this fly and impedes my flight. If I wish to reach my nest quickly, I must get rid of them—to effect which, the shortest way will be to alight again and cut them off." These reflections, or others of similar import, must be supposed to have passed through the mind of the wasp, or its actions are altogether inexplicable. Instinct might have taught it to cut off the wings of all flies, previously to flying away with them. But here it first attempted to fly with the wings on,—was impeded by a certain cause,—discovered what this cause was,—and alighted to remove it. The chain of evidence seems perfect in proof that nothing but reason could have been its prompter.
An analogous though less striking fact is mentioned by Reaumur on the authority of M. Cossigny, who witnessed it in the Isle of France where the Sphecina are accustomed to bury the bodies of cockroaches along with their eggs for provision for their young. He sometimes saw an insect of this tribe attempt to drag after it into its hole a dead cockroach, which was too big to be made to enter by all its efforts. After several ineffectual trials the animal came out, cut off its elytra and some of its legs, and thus reduced in compass drew in its prey without difficulty[815].
Under this head I shall mention but one fact more.—A friend of Gleditsch the observer of the singular economy of the burying beetle (Necrophorus Vespillo) related in a former letter[816], being desirous of drying a dead toad, fixed it to the top of a piece of wood which he stuck into the ground. But a short time afterwards, he found that a body of these indefatigable little sextons had circumvented him in spite of his precautions. Not being able to reach the toad, they had undermined the base of the stick until it fell, and then buried both stick and toad[817].
In the second place, insects gain knowledge from experience, which would be impossible if they were not gifted with some portion of reason. In proof of their thus profiting, I shall select from the numerous facts that might be brought forward, two only, one of which has been already slightly adverted to[818].
M. P. Huber, in his valuable paper in the sixth volume of the Linnean Transactions[819], states that he has seen large humble-bees, when unable from the size of their head and thorax to reach to the bottom of the long tubes of the flowers of beans, go directly to the calyx, pierce it as well as the tube with the exterior horny parts of their proboscis, and then insert their proboscis itself into the orifice and abstract the honey. They thus flew from flower to flower, piercing the tubes from without, and sucking the nectar, while smaller humble-bees or those with a longer proboscis entered in at the top of the corolla. Now from this statement it seems evident, that the larger bees did not pierce the bottoms of the flowers until they had ascertained by trial that they could not reach the nectar from the top; but that having once ascertained by experience that the flowers of beans are too strait to admit them, they then, without further attempts in the ordinary way, pierced the bottoms of all the flowers which they wished to rifle of their sweets.—M. Aubert du Petit-Thouars observed that humble-bees and the carpenter-bee (Xylocopa[820] violacea) gained access in a similar manner to the nectar of Antirrhinum Linaria and majus, and Mirabilis Jalappa; as do the common bees of the Isle of France to that of Canna indica[821]; and I have myself more than once noticed holes at the base of the long nectaries of Aquilegia vulgaris, which I attribute to the same agency.
My second fact is supplied by the same ants, whose sagacious choice of the vicinity of Reaumur's glass hives for their colony has been just related to you. He tells us that of these ants, of which there were such swarms on the outside of the hive, not a single one was ever perceived within; and infers that, as they are such lovers of honey, and there was no difficulty in finding crevices to enter in at, they were kept without, solely from fear of the consequences[822]. Whence arose this fear? We have no ground for supposing ants endowed with any instinctive dread of bees; and Reaumur tells us, that when he happened to leave in his garden, hives of which the bees had died, the ants then never failed to enter them and regale themselves with the honey. It seems reasonable, therefore, to attribute it to experience. Some of the ants no doubt had tried to enter the peopled as they did the empty hive, but had been punished for their presumption, and the dear-bought lesson was not lost on the rest of the community.
Insects, in the third place, are able mutually to communicate and receive information, which, in whatever way effected, would be impracticable if they were devoid of reason. Under this head it is only necessary to refer you to the endless facts in proof, furnished by almost every page of my letters on the history of ants and of the hive-bee. I shall therefore but detain you for a moment with an additional anecdote or two, especially with one respecting the former tribe, which is valuable from the celebrity of the relater.