Our Common Insects Part 2

[Ill.u.s.tration: 23. Larva of Ceratina.]

[Ill.u.s.tration: 24. Nest of Tailor Bee.]

In none of the wild bees are the cells constructed with more nicety than those of our little Ceratina. She bores out with her jaws a long deep well just the size of her body, and then stretches a thin, delicate cloth of silk drawn tight as a drum-head across each end of her chambers, which she then fills with a mixture of pollen and honey.

[Ill.u.s.tration: 25. Tailor Bee.]

Her young are not, in this supposed retreat, entirely free from danger.

The most invidious foes enter and attack the brood. Three species of Ichneumon flies, two of which belong to the Chalcid family, lay their eggs within the body of the larva, and emerge from the dried larva and pupa skins of the bee, often in great numbers. The smallest parasite, belonging to the genus Anthophorabia, so called from being first known as a parasite on another bee (Anthophora), is a minute species found also abundantly in the tight cells of the Leaf-cutter bee.

The interesting habits of the Leaf-cutting, or Tailor bee (Megachile), have always attracted attention. This bee is a stout, thick-bodied insect, with a large, square head, stout, sharp, scissors-like jaws, and with a thick ma.s.s of stout, dense hairs on the under side of the tail for carrying pollen, as she is not provided with the pollen-basket of the Honey and Humble bees.

The Megachile lays its eggs in burrows in the stems of the elder (Fig.

24), which we have received from Mr. James Angus; we have also found them in the hollows of the locust tree. Mr. F. W. Putnam thus speaks of the economy of M. centuncularis, our most common species. "My attention was first called, on the 26th of June, to a female busily engaged in bringing pieces of leaf to her cells, which she was building under a board, on the roof of the piazza, directly under my window. Nearly the whole morning was occupied by the bee in bringing pieces of leaf from a rose bush growing about ten yards from her cells, returning at intervals of a half minute to a minute with the pieces, which she carried in such a manner as not to impede her steps when she alighted near her hole."

When the Leaf-cutter bee wishes to cut out a piece of a leaf (Fig. 25) she alights upon the leaf, and in a few seconds swiftly runs her scissors-like jaws around through it, bearing off the piece in her hind legs. "About noon she had probably completed the cell, upon which she had been engaged, as, during the afternoon, she was occupied in bringing pollen, preparatory to laying her single egg in the cell. For about twenty days the bee continued at work, building new cells and supplying them with pollen.... On the 28th of July, upon removing the board, it was found that the bee had made thirty cells, arranged in nine rows of unequal length, some being slightly curved to adapt them to the s.p.a.ce under the board. The longest row contained six cells, and was two and, three-quarters inches in length; the whole leaf structure being equal to a length of fifteen inches. Upon making an estimate of the pieces of leaf in this structure, it was ascertained that there must have been at least a thousand pieces used. In addition to the labor of making the cells, this bee, una.s.sisted in all her duties, had to collect the requisite amount of pollen (and honey?) for each cell, and lay her eggs therein, when completed. Upon carefully cutting out a portion of one of the cells, a full-grown larva was seen engaged in spinning a slight silken coc.o.o.n about the walls of its prison, which were quite hard and smooth on the inside, probably owing to the movements of the larva, and the consequent pressing of the sticky particles to the walls. In a short time the opening made was closed over by a very thin silken web. The cells, measured on the inside of the hard walls, were .35 of an inch in length, and .15 in diameter. The natural att.i.tude of the larva is somewhat curved in its cell, but if straightened, it just equals the inside length of the cell. On the 31st of July, two female bees came out, having cut their way through the sides of their cells." In three other cells "several hundred minute Ichneumons (Anthophorabia megachilis) were seen, which came forth as soon as the cells were opened."

The habits of the little blue or green Mason bees (Osmia) are quite varied. They construct their cells in the stems of plants, and in rotten posts and trees, or, like Andrena, they burrow in sunny banks. A European species selects snail sh.e.l.ls for its nest, wherein it builds its earthen cells, while other species nidificate under stones. Curtis found two hundred and thirty coc.o.o.ns of a British species (Osmia paretina), placed on the under side of a flat stone, of which one-third were empty. Of the remainder, the most appeared between March and June, males appearing first; thirty-five more bees were developed the following spring. Thus there were three successive broods, for three succeeding years, so that these bees lived three years before arriving at maturity. This may partly account for _insect years_, which are like "apple years," seasons when bees and wasps, as well as other insects, abound in unusual numbers.

[Ill.u.s.tration: 26. Nest of Osmia.]

Mr. G. R. Waterhouse, in the Transactions of the Entomological Society of London, for 1864, states that the cells of Osmia leucomelana "are formed of mud, and each cell is built separately. The female bee, having deposited a small pellet of mud in a sheltered spot between some tufts of gra.s.s, immediately begins to excavate a small cavity in its upper surface, sc.r.a.ping the mud away from the centre towards the margin by means of her jaws. A small, shallow mud-cup is thus produced. It is rough and uneven on the outer surface, but beautifully smooth on the inner. On witnessing thus much of the work performed, I was struck with three points: first, the rapidity with which the insect worked; secondly, the tenacity with which she kept her original position whilst excavating; and thirdly, her constantly going over work which had apparently been completed.... The lid is excavated and rendered concave on its outer or upper surface, and is convex and rough on its inner surface; and, in fact, is a simple repet.i.tion of the first-formed portion of the cell, a part of a hollow sphere."

The largest species of Osmia known to us is a very dark-blue species (O.

lignivora). We are indebted to a lady for specimens of the bees with their cells, which had been excavated in the interior of a maple tree several inches from the bark. The bee had industriously tunnelled out this elaborate burrow (Fig. 26), and, in this respect, resembled the habits of the Carpenter bee more closely than any other species of its genus.

The tunnel was over three inches long, and about three-tenths of an inch wide. It contracted a little in width between the cell, showing that the bee worked intelligently, and wasted no more of her energies than was absolutely necessary. The burrow contained five cells, each half an inch long, being rather short and broad, with the hinder end rounded, while the opposite end, next to the one adjoining, is cut off squarely. The cell is somewhat jug-shaped, owing to a slight constriction just behind the mouth. The material of which the cell is composed is stout, silken, parchment-like, and very smooth within. The interstices between the cells are filled in with rather coa.r.s.e chippings made by the bee.

The bee cut its way out of the cells in March, and lived for a month afterwards on a diet of honey and water. It eagerly lapped up the drops of water supplied by its keeper, to whom it soon grew accustomed, and seemed to recognize.

Our smallest and most abundant species is the little green Osmia simillima. It builds its little oval, somewhat urn-shaped cells against the roof of the large deserted galls of the oak-gall fly (Diplolepis confluentus), placing them, in this instance eleven in number, in two irregular rows, from which the mature bees issue through a hole in the gall (Fig. 27, with two separate cells). The earthen cells, containing the tough dense coc.o.o.ns, were arranged irregularly so as to fit the concave vault of the larger gall, which was about two inches in diameter. On emerging from the cell the Osmia cuts out with its powerful jaws an ovate lid, nearly as large as one side of the cell.

[Ill.u.s.tration: 27. Nest of Osmia in a gall.]

In the Harris collection are the cells and specimens of Osmia pacifica, the peaceful Osmia, which, according to the ma.n.u.script notes of Dr.

Harris, is found in the perfect state in earthen cells beneath stones.

The cell is oval cylindrical, a little contracted as usual with those of all the species of the genus, thus forming an urn-shaped cell. It is half an inch long, and nearly three-tenths of an inch wide, while the coc.o.o.n, which is rather thin, is three-tenths of an inch long. We are not acquainted with the habits of the larva and pupa in this country, but Mr. F. Smith states that the larva of the English species hatches in eight days after the eggs are laid, feeds ten to twelve days, when it becomes full-grown, then spins a thin silken covering, and remains in an inactive state until the following spring, when it completes its transformations.

In the economy of our wild bees we see the manifestation of a wonderful instinct, as well as the exhibition of a _limited reason_. We can scarcely deny to animals a kind of reason which apparently differs _only in degree_ from that of man. Each species works in a sphere limited by physical laws, but within that sphere it is a free agent. They have enough of instinct and reason to direct their lives, and to enable them to act their part in carrying out the plan of creation.

[Ill.u.s.tration: Paper Wasp.]

FOOTNOTES:

[Footnote 1: The cells are not perfectly hexagonal. See the studies on the formation of the cells of the bee, by Professor J. Wyman, in the Proceedings of the American Academy of Arts and Sciences, Boston, 1866; and the author's Guide to the Study of Insects, p 123.]

[Footnote 2: Notes on the Habits of the Humble Bee (Proceedings of the Ess.e.x Inst.i.tute, vol. iv, 1864, p. 101).

Mr. Angus also writes us as follows concerning the habits of the Wandering Humble bee (Bombus vagans): "I have found the males plentiful near our garden fence, within a hole such as would be made by a mouse.

They seem to be quite numerous. I was attracted to it by the noise they were making in fanning at the opening. I counted at one time as many as seven thus employed, and the sound could be heard several yards off.

Several males were at rest, but mostly on the wing, when they would make a dash among the fanners, and all would scatter and play about. The workers seem to be of a uniform size, and full as large as the males. I think the object of the fanning was to introduce air into the nest, as is done by the Honey bees."]

[Footnote 3: "Since writing the above I have opened one of the new holes of Xylocopa, which was commenced between three and four weeks ago, in a pine slat used in the staging of the greenhouse. The dimensions were as follows:--Opening fully 3-8 wide; depth 7-16; whole length of tunnel 6 5-16 inches. The tunnel branched both ways from the hole. One end, from opening, was 2 5-8, containing three cells, two with larva and pollen, the third empty. The other side of the opening, or the rest of the tunnel, was empty, with the exception of the old bee (only one) at work.

I think this was the work of one bee, and, as near as I can judge, about twenty-five days' work. Width of tunnel inside at widest 9-16 inch.

"I have just found a Xylocopa bobbing at one of the holes, and in order to ascertain the depth of the tunnel, and to see whether there were any others in them, I sounded with a pliable rod, and found others in one side, at a depth of five and one half inches; the other side was four inches deep without bees. The morning was cool, so that the object in bobbing could not have been to introduce fresh currents of air, but must have had some relation to those inside. Their legs on such occasions are, as I have noticed, loaded with pollen."]

CHAPTER II.

THE HOME OF THE BEES.

[_Concluded._]

While the Andrena and Halictus bees, whose habits we now describe, are closely allied in form to the Hive bee, socially they are the "mud-sills" of bee society, ranking among the lowest forms of the family of bees. Their burrowing habits ally them with the ants, from whose nests their own burrows can scarcely be distinguished. Their economy does not seem to demand the exercise of so much of a true reasoning power and pliable instinct as characterizes bees, such as the Honey and Humble bee, which possess a high architectural skill. Moreover they are not social; they have no part in rearing and caring for their young, a fact that lends so much interest to the history of the Hive and Humble bee. In this respect they are far below the wasps, a family belonging next below in the system of Nature.

A glance at the drawing (Fig. 28), of a burrow, with its side galleries, of the Andrena vicina, reveals the economy of one of our most common forms. Quite early in spring, when the sun and vernal breezes have dried up the soil, and the fields exchange their rusty hues for the rich green verdure of May, our Andrena, tired of its idle life among the blossoms of the willow, the wild cherry, and garden flowers, suddenly becomes remarkably industrious, and wields its spade-like jaws and busy feet with a strange and unwonted energy. Choosing some sunny, warm, gra.s.sy bank (these nests were observed in the "great pasture" of Salem), not always with a southern exposure however, the female sinks her deep well through the sod from six inches to a foot into the sandy soil beneath.

She goes to work literally tooth and nail. Reasoning from observations made on several species of wasps, and also from studying the structure of her jaws and legs, it is evident that she digs in and loosens the soil with her powerful jaws, and then throws out the dirt with her legs.

She uses her fore legs like hands, to pa.s.s the load of dirt to her hind legs, and then runs backward out of her hole to dump it down behind her.

Mr. Emerton tells me that he never saw a bee in the act of digging but once, and then she left off after a few strokes. He also says, "they are harmless and inoffensive. On several occasions I have lain on the gra.s.s near their holes for hours, but not one attempted to sting me; and when taken between the fingers, they make but feeble resistance."

[Ill.u.s.tration: Fig. 28.

Nest (natural size) of Andrena vicina, showing the main burrow, and the cells leading from it; the oldest cell containing the pupa (_a_) is situated nearest the surface, while those containing the larva (_b_) lie between the pupa and the cell (_e_) containing the pollen ma.s.s and egg resting upon it. The most recent cell (_f_) is the deepest down, and contains a freshly deposited pollen ma.s.s. At _c_ is the beginning of a cell; _g_, level of the ground.]

To enter somewhat into detail, we gather from the observations of Mr.

Emerton (who has carefully watched the habits of these bees through several seasons) the following account of the economy of this bee: On the 4th of May the bees were seen digging their holes, most of which were already two inches deep, and one, six inches. The mounds of earth were so small as to be hardly noticed. At this time an Oil beetle was seen prowling about the holes. The presence of this dire foe of Andrena at this time, it will be seen in a succeeding chapter on the enemies of the bees, is quite significant. By the 15th of May, hundreds of Andrena holes were found in various parts of the pasture, and at one place, in a previous season, there were about two hundred found placed within a small area. One cell was dug up, but it contained no pollen. Four days later, several Andrenas were noticed resting from their toil at the opening of their burrows. On the 28th of May, in unearthing six holes, eight cells were found to contain pollen, and in two of them a small larva. The pellets of pollen are about the size of a small pea. They are hard and round at first, before the young has hatched, but as the larva grows, the ma.s.s becomes softer and more pasty, so that the larva buries its head in the ma.s.s, and greedily sucks it in. When is the pollen gathered by the bee and kneaded into the pellet-like ma.s.s? On July 4th, a cell was opened in which was a bee busily engaged preparing the pollen, which was loosely and irregularly piled up, while there was a larva in an adjoining cell nearly half an inch long. It would seem, then, that the bee comes in from the fields laden with her stores of pollen, which she elaborates into bee bread within her cell.

When the bee returns to her cell she does not directly fly towards the entrance, since, as was noticed in a particular instance, she flew about for a long time in all directions without any apparent aim, until she finally settled near the hole, and walked into her subterranean retreat.

On a rainy day, May 24th, our friend visited the colony, but found no bees flying about the holes. The little hillocks had been beaten down by the pitiless raindrops, and all traces of their industry effaced. On digging down, several bees were found, indicating that on rainy days they seek the shelter of their holes, and do not take refuge under leaves of the plants they frequent.

On the 29th of June, six full-grown larvae were exhumed, and one, about half grown. On the 20th of July, the colony seemed well organized, as, on laying open a burrow at the depth of six inches, he began to find cells. The upper ones, to the number of a dozen, were deserted and filled with earth and gra.s.s roots, and had evidently been built and used during the previous year. Below these were eight cells placed around the main vertical gallery, reaching down to the depth of thirteen inches, and all containing nearly full-grown larvae of the bees, or else those of some parasitic bee (Nomada) which had devoured the food prepared for the young Andrena.

About the first of August the larva transforms to a pupa or chrysalis, as at this time two pupae were found in cells a foot beneath the surface.

As shown in the cut, those cells situated lowest down seem to be the last to have been made, while the eggs laid in the highest are the first to hatch, and the larvae disclosed from them, the first to change to pupae. Four days later the pupae of Cuckoo bees (Nomada) were found in the cells. No Andrenas were seen flying about at this time.

On the 24th of August, to be still very circ.u.mstantial in our narrative though at the risk of being tedious, three burrows were unearthed, and in them three fully formed bees were found nearly ready to leave their cells, and in addition several pupae. In some other cells there were three of the parasitic Nomada also nearly ready to come out, which seemed to be identical with some bees noticed playing very innocently about the holes early in the summer.

On the last day of August, very few of the holes were open. A number of Oil beetles were strolling suspiciously about in the neighborhood, and some little black Ichneumon flies were seen running about among the holes.

During mid-summer the holes were found closed night and day by clods of earth.

The burrow is sunken perpendicularly, with short pa.s.sages leading to the cells, which are slightly inclined downwards and outwards from the main gallery. The walls of the gallery are rough, but the cells are lined with a mucous-like secretion, which, on hardening, looks like the glazing of earthenware. This glazing is quite hard, and breaks up into angular pieces. It is evidently the work of the bee herself, and is not secreted and laid on by the larva. The diameter of the interior of the cell is about one-quarter of an inch, contracting a little at the mouth.

When the cell is taken out, the dirt adheres for a line in thickness, so that it is of the size and form of an acorn.

The larva of Andrena (Fig. 29) is soft and fleshy, like that of the Honey bee. Its body is flattened, bulging out prominently at the sides, and tapering more rapidly than usual towards each end of the body. The skin is very thin, so that along the back the heart or dorsal vessel may be distinctly seen, pulsating about sixty times a minute.