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PRETTY little wasps, shaped and coloured more like yellow-jackets than mud-daubers, construct their nests in wood, burrowing into logs or boards and there chipping out a cavity large enough to contain the egg and its provisions.
They are usually of small size, with black, shining bodies ringed with one or more bands of yellow.
Some of them are so yellow-jacket-like in appearance that their occupation is all that distinguishes them to the eye of the hasty observer.
They are pretty, busy little creatures, very alert and quick in their movements. Their heads are much larger in proportion than the heads of the yellow-jackets, and they have large, strong jaws, as is necessary to carpenters that work with their heads instead of their hands.
One spring a number of them took a fancy to drill into the logs of a cabin on a mountain top in the western part of Virginia.
The first one that appeared upon the scene was a slender little creature, about half the length of a mud-dauber.
She went about examining the log, evidently with a view to settlement.
She poked into every little worm-hole and cranny in the bark, and was a long time in finding a place to her liking.
At last she succeeded, and then the chips began to fly.
She found a little hole not large enough and not deep enough, and this she proceeded to develop into a nest.
She bit out particles of wood with her strong jaws. When she had loosened a chip or a fibre, she backed out of her hole, flew away a few feet, and dropped it; then she returned and gnawed out another fibre, or else cut little bits like fine saw-dust. She always crept into her hole head first, and backed out tail first, losing no time and wasting no energy in superfluous motions. And she always flew away with her chips, and dropped them some distance from her door.
Had she littered up her doorway, the traces of her labour might have betrayed her to the enemy.
For there is always an enemy lying in wait for the miners.
This enemy is an exceedingly beautiful little rascal about as large as a house-fly, and of a brilliant metallic green.
It, too, belongs to the Order Hymenoptera, though it is not at the wasp end of that division.
It is a Chrysis fly, that, instead of making a nest for itself, dogs the miner wasps, and watches with interest the progress of its neighbour's nursery. As soon as the hole in the log is finished, the first insect stored away, and the wasp gone for another, in pops little green madam. She lays her egg in the snug retreat that cost her only vigilance to secure, and away she goes.
But woe to her if she is caught in the act, for the wasp knows her well and understands perfectly her thievish intentions, and if she so much as sees her in the neighbourhood of the nest there is trouble. The wasp makes a dash for the chrysis, but the little green rascal is so very quick in her movements that she generally escapes unharmed.
She appears to go away after this inhospitable reception, but she does not really go. She still lurks near, watching operations -- and watching her chance.
If she succeeds in getting into the nest when the wasp is away she deposits her egg, and her interest in that nest is at an end.
The wasp goes on provisioning what she believes to be the larder of her own offspring, wholly unconscious that the chrysis has outwitted her, and that she is labouring for the progeny of her hated foe.
When the Virginia wasp had finished the nest, stored it with provisions and laid her egg, she carefully sealed the entrance with mud and went away, leaving her progeny to care for itself.
She spent part of two days making her nest:
At first she was shy and would not work when closely observed, but she soon lost all fear of her human friends, and burrowed away as if she had the whole place to herself. She often stopped to rest and to sip the nectar from wild flowers that grew near the door-step.
The second morning of her work was rainy, and like all her tribe, she declined to expose her person to the storm; but when the sun shone out in the afternoon, there was the little carpenter as busy and as alert as ever.
In course of time the egg hidden with so much care in the wood hatches. The larva, in as impregnable a fortress as any one could desire, begins at once upon the delightful occupation of consuming luscious flies or aphides, or whatever delectable pabulum its mother has stored up for it.
It eats and grows. Having nothing to do but eat, and being so constituted that it does not suffer from the lack of other exercise, it grows rapidly.
Like the other wasp larvae it is a little white, legless grub, and at length, having eaten up everything it can find, it spins itself a silken cocoon in which to undergo the transformations that will cause it to become a perfect wasp, with all the organs and powers and desires of a wasp.
Its cocoon has sometimes been found gay with the wings of the insects it has eaten, which are woven into its silken covering; and sometimes it uses the chips of wood it may find in its nest in the same way.
Whether it considers these additions ornamental, or whether it uses them to get them out of the way, itself alone knows.
When the transformation is completed, the mud cap is gnawed away and forth from the log issues a young wasp.
These things happen to a larva into whose nest no chrysis has found place. Where the chrysis egg is laid in the nest there is another story to tell.
The vigorous young chrysis devours the food intended for the wasp - and incidentally devours the wasp too.
Now matters go on as before, only that a changeling occupies the cradle. It eats and grows - it becomes a pupa -- transforms to an adult chrysis --bites its way out through the mud cap, and comes forth -- ready to try for its own offspring the clever but thievish experiment by which its infancy was so well nourished at so little cost to its mother.
These little green chryses are so quick in their movements that it is extremely difficult to catch them even with a net. They are outlaws by nature, and have the craft and fleetness acquired by outlaws, whether those picturesque products of nature are human or hymenopteran.
Their brilliant dress flashing in the sun betrays these wicked Robin Hoods at a glance, but they are bold and fearless, and wear their glistening attire with as devil-may-care a grace as did the outlaws of the greenwood of old.
The wasps chisel out a separate hole for each egg laid, and about an equal number of both sexes are hatched, as is the case with nearly all the solitary wasps.
The males, as is true of most wasps, soon die, leaving their mates to carry on the affairs of the family.
It is always the female that digs out the holes in the wood and catches and stings the insects she puts in as food. The male, having no sting, could not assist in the provisioning of his household even if his life were sufficiently prolonged.
The wasp leads a busy and arduous life, and also a precarious one, as witness the innumerable little nests of the various species that have been begun but never finished.
On the logs of the Virginia cabin came another species of miner wasp, smaller than the first, but otherwise closely resembling it.
This little one made a tiny hole, just as the larger one had done, but when it had finished it lined its nest with a gluey material from its own mouth and sealed it -not with mud -but with a glistening substance like the lining.
It was not discovered what these nests were provisioned with, as neither wasp was caught in the act of carrying in its booty, and it would have been very difficult to cut the nests out, as well as disfiguring to the cabin.
Another miner wasp, with a strikingly yellow-jacket-like appearance, was seen later in the summer carrying something into a little hole between the shingles on a New England sea-shore house.
She went in so quickly, however, that it was not possible to discover the nature of her victim. When she had. carried in a number of small insects she closed the opening and went away.
In choosing the neat little tunnel made by the shingles where they did not quite come together and were roofed over by the shingle above, this clever wasp saved herself the trouble of digging out her own hole.
But clever as she was, she may not have been clever enough to escape the brilliant green little rascal that lay in wait. For she too had her chrysis, that ran swiftly about in her absence, evidently scenting the wasp whose retreat she could not find. Whether Robin Hood did or did not find the right hole between the shingles in time to defraud the wasp of her honest labours, could not be discovered.
The carpenter or wood-boring wasps frequently use any convenient opening for their nests, some having been discovered occupying holes in the mortar of a brick wall.
Trypoxylon is a slender-waisted black little carpenter, ornamented with a red girdle in one species, and with white hairs on her legs in another. The red-girdled Trypoxylon, or rubrocinctum, was one summer watched making her nests in a straw-stack. “The stack had been cut off perfectly smooth on one side, so that many thousands of the cut ends of the straws were exposed to view, and these proved very attractive to rubrocinctum.”
These wasps provision their nests with spiders, and with mud partition their tunnels into compartments. With them the males are not the idle members of society that they are with so many of the wasps. The female still makes the nest, or selects the straw, as the case may be, provisions and partitions it, but greatly to his credit be it said, “When the preliminary work of clearing the nest and erecting the inner partition has been performed by the female, the male takes up his station inside the cell, facing outward, his little head just filling the opening. Here he stands on guard for the greater part of the time until the nest is provisioned and sealed up, occasionally varying the monotony of his task by a short flight. As a usual thing all the work is performed by the female, who applies herself to her duties with greater or less industry according to her individual character; but the male doubtless discharges an important office in protecting the nest from parasites. We have frequently seen him drive away the brilliant green Chrysis fly, which is always waiting about for a chance to enter an unguarded nest. On these occasions the defence is carried on with great vigour, the fly being pursued for some distance into the air. There are usually two or three unmated males flying about in the neighbourhood of the nests, poking their heads into unused holes, and occasionally trying to enter one that is occupied, but never, so far as we have seen, with any success, the male in charge being always quite ready and able to take care of his rights. The males, however, made no objection when strange females entered the nest, as they sometimes did by mistake, nor did the females object to the entrance of a strange male when the one belonging to the nest happened to be away, but in such cases the rightful owner, on his return, quickly ejected the intruder. We often amused ourselves, while we were watching the nests, by approaching the little male, as he stood in his doorway, with a blade of grass. He always attacked it valiantly, and sometimes grasped it so tightly in his mandibles that he could be drawn out of the nest with it.
“When the female returns to the nest with a spider the male flies out to make way for her, and then as she goes in he alights on her back and enters with her. When she comes out again she brings him with her, but he at once re-enters, and then, after a moment, comes out and backs in, so that he faces outward as before.
“In one instance, with rubrocinctum, when the work of storing the nest had been delayed by rainy weather, we saw the male assisting by taking the spiders from the female as she brought them, and packing them into the nest, leaving her free to hunt for more. This was an especially attentive little fellow, as he guarded the nest almost continuously for four days, the female sometimes being gone for hours at a time. On the last day he even revisited the nest three or four times after it had been sealed up.”
These wasps sing merrily while packing away the spiders in their narrow tunnels, and in the case of those inhabiting the straw-stack, the little mother often searched for some time before finding her own particular straw, sometimes going into other wasps' straws a number of times before coming to her own doorway. One should think it might be puzzling to locate the exact straw out of a whole stack of them. And this straw-stack was estimated to be the mausoleum of from six to twelve thousand spiders!
While most of the wood-borers are small wasps, there are some giants of the race that bore holes several inches long in solid wood, and naturally these are not regarded with favour by man, as they spoil the timber into which they tunnel.
One sometimes breaks the dry stalk of an elder, bramble, sumac, or other pithy plant, to find the central cavity partitioned into compartments and stuffed with motionless insects. The meaning of this is evident. One of the carpenter wasps has been at work fitting up its nursery; for certain species of them prefer a hollow twig to any other building-place. Somewhere in each compartment is an egg, or it may be a larva has already hatched and is contentedly eating its way to adult waspdom through its roomful of stored-up insects. Later these larvae will have spun themselves cocoons, and will go through the pupal stage common to all wasps, and later with their strong adult jaws will gnaw out of their prison cells, and soon after will gnaw into other dead branches in the interest of their own progeny.
A very pretty story is told about one of these little stem-tunnelling wasps, the Crabro stirpicola, a tiny creature only a quarter of an inch long, with a black and yellow banded body and yellow legs. She was found at half-past five o'clock in the afternoon, when she had just begun her excavation. “Her manners were an agreeable contrast to those of the wasps that we had been watching through the day. The feverish excitement of their ways seemed quite, in keeping with the burning heat of noon, while Crabro's slow and gentle movements harmonised perfectly with the long shadows of evening.”
But Crabro was persevering, if not tempestuous; she bit out the pith with her jaws, and when a quantity had accumulated, backed out, pushing it behind her and kicking it away with her hind legs. The hours wore on and still Crabro bit and shoved and kicked out pellets of pith. Others might sleep at night and work like whirlwinds in the daytime; she, calm and steady, worked all night long, and all the next day, and all the next night, and part of the third day, stopping only ten minutes for refreshments during her forty-two-hour task.
She was watched closely all this time, a bottle to catch her chips being put over the stem at night to record her progress, and if she grew not weary her observers did. “We began to wonder if she would ever finish her task. Wonderful though she was, we had grown a little weary of our long session of watching. We had been glad that she worked through the first night; it was creditable to her and interesting to us, and we admired her even more for sticking to it through the second, but when it looked as though we might have to remain by her side through another long day, watching an endless series of loads as they were carried out, we confess that we thought she was rather overdoing it. Gradually, however, she slowed up her work, taking two or three minutes to make a journey down and up. At last, at just nine o'clock, her head appeared at the top of the stalk, and after a slight hesitation she flew away. The nest was completed.”
This industrious pygmy is quite an exception in wasp annals, for as a rule the wasps retire at sunset and rest until the sun is well up in the morning, though the social wasps under pressure of communal cares sometimes fly until it is quite dark, and are abroad at daybreak.
All will agree that Crabro Stirpicola deserved the eulogium passed upon her by her patient watchers: “Surely she takes the palm for industry, not only from other wasps, but from the ant and bee as well.”
Although the nest was excavated, little Crabro's labours were not over, for it had to be provisioned, and for the next three or four days she was industriously seeking, catching, and storing flies. Let us hope that between times she rested on some lovely flower-cluster, and refreshed herself with nectar.
The end of her little drama is tragic, as so often happens with the wasps. She succeeded in stocking one cell, laying one egg, and closing the compartment with pith, and that was all; she went forth never to return. What happened to her, nobody knows, but somewhere in the big world where evil creatures lie in wait for little wasps, she met her death.
Her tunnel was thirty-nine centimetres in length, long enough to allow of ten or twelve compartments, one above another.
Where wasps partition long tunnels into a number of cells, the egg last laid is near the entrance, and one wonders how the wasps from the first-laid eggs at the other end of the tunnel are able to get out. In wasp life this seemingly difficult problem has been easily solved.
The wasp from the last-laid egg is the first to mature.
The last wasp in is the first wasp out. The one next behind matures next, gnaws through its cap, finds itself in its neighbour's empty cell, through which it crawls to the outer world. The next wasp in succession comes through two empty cells, and so on, until all are safely out. Usually there are not more than four or five of these adjoining compartments.
Wasps use a variety of materials in lining and closing their cells. Some are found lined with a white, cottony, felt-like substance, some with a gluey material, some with a silken, web-like substance, and some are not lined at all.
To those having time, and inclination, there is opportunity; much original investigation in the habits of the solitary wasps.
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