The male Humble-Bees are not reared till late in the season, and do not appear in any abundance till the autumn. As in the case of the hive-bee therefore, they take no part in the duties of rearing the young, which it appears are almost entirely under the protection of the neuters as soon as they are hatched.
When the nest is tolerably well peopled, it presents a mass of oval cocoons spun by the larva' as before described ; interspersed with which there are numerous masses of an irregular but generally some what rounded form, and of a brown colour : some of the largest are about the size of a small walnut. Each of these masses inclose' either eggs or larva', and is composed of pollen mixed with honey. To these must be added the little honey-pots which are irregularly interspersed with the cocoons.
BOMBI"CIDeE, a family of Insects of the order Lepidoptera, belonging to the section Lepidoptera voeturna of Latreille, or Moths.
The principal characteristics of this family are—their possessing only /11, rudimentary maxilla', remarkably small palpi, and bipeetinated antennx.
The Silkworm is about eight weeks in arriving at maturity, during which period it changes its skin four or five times. When about to cast its skin it ceases to eat, raises the fore part of the body slightly, and remains in perfect repose. In this state it is necessary that it should continue for some little time, in order that the new skin, which is at this time forming, may become sufficiently mature to enable the caterpillar to burst through the old one. This operation, which is apparently one of considerable difficulty, is performed thus :—the fore part of the old skin is burst ; the silkworm then by continually writhing its body (but not moving from the spot) contrives to thrust the skin back to the tail, and ultimately to disengage itself altogether ; this last part of the operation however is the most difficult, since it is no uncommon occurence for them to die from not being able to disengage the last segment of the body from the old skin.
Those who have reared silkworms must have observed how large the head is in proportion to the body in those which have just changed their skins; this circumstance is worthy of observation, for in it will be found a most beautiful contrivance.
When the larva of an insect has just changed its skin, every part is soft, and in many cases (such as caterpillars) the greater portion of the body still remains in this flexible state ; but the skin of the head and some few other parts in all instances soon become hardened, after which it never grows. The same happens with those larvae which have the body in a great measure covered with hard plates, which circumstance leaves no parts to enlarge but such as are flexible. In the instance of
caterpillar the body increases in size rapidly after change of skin, but the bead it will be observed does not enlarge, and although the body may have increased very much it does not appear that the skin has grown ; it seems only to be stretched with the increase of size of the inner parts. In the case of those lame which have the body covered with hard plates, it is the skin between the plates that stretches to allow of growth in the inner parts, so that just before changing skin all the plates are considerably separated.
From the above we conclude that the external covering of insects does not grow at all, except at the time of repose previous to the casting off the old skin, after which operation the head and those parte which soon become hard are sufficiently grown to last until the next change ; and also that the soft parts of the external covering will bear stretching to a certain extent and no further when it becomes necessary that they should change that covering for a larger one.
With respect to the silkworm and other caterpillars, an unobserving person would not readily understand how the head, which is much larger than the one the case of which has just been cast off; can have come out of it ; but if the silkworm be examined just before it is about to change its skin, it will be seen that such is not exactly the case, for part of the new head may be seen thrust out behind the old one, so that the fore part only is inclosed by the latter.
When full grown the silkworm commences spinning its web in some convenient spot, and as it does not change the position of the hinder portion of its body much, but continues drawing its thread from various points and attaching it to others, it follows that after a time its body becomes in a great measure inclosed by the thread. The work is then continued from one thread to another, the silkworm moving its head and spinning in a zigzag way, bending the fore part of the body back to spin in all directions within reach, and shifting the body only to cover with silk the part which was beneath it. As the silkworm spins its web by thus bending the fore part of the body back, and moves the hinder part of the body iu such a way only as to enable it to reach the farther back with the fore part, it follows that it incloses itself in a cocoon much shorter than its own body, for soon after the beginning the whole is continued with the body in a bent position. From the foregoing account it appears that with the most simple instinctive principles all the ends necessary are gained.