In the Gentleman's Magazine for the year 1764 we read that "a kind of rain of a red colour, resembling blood, fell in many parts of the Duchy of Cleves, and caused great consternation. Something of the like kind fell also at Rhenen, in the province of Utrecht." A gentleman is reported to have sent a bottle full of it to Dr. Schutte, to know if it contained anything pernicious to health. Dr. Schutte wrote a learned dissertation upon it, and gave it as his opinion that it was caused by the particles which had been raised into the atmosphere by a strong wind, and that it was in no way hurtful to mankind or beasts. Probably butterflies were the real shedders of this blood-like shower, as in the previous cases.[T]
Our next remark about the imago state of insects will, perhaps, create some surprise—Insects in this state, with some apparent exceptions, do not grow larger. When they leave the pupa state, and have all their parts fully developed, they do not subsequently increase in size. We are often told by ignorant people that the little house-flies which we watch dancing in our chambers, or scrambling up our windows, are only young flies of the same kind as flesh-flies, and that by-and-by they will grow into a large "Blue-bottle!" This is a sad mistake. Let the reader try. Let a fly be put under a glass, and fed with a little sugar, or honey: in vain will he daily examine it, in the expectation of beholding it increase in size—it will live and die nearly the same little being unaltered to the last. If such persons only knew somewhat of the life of an insect, such an absurd, and, unfortunately, very prevalent mistake would not be committed. We might as reasonably call a trout a young salmon! If we were to examine any number of flies of the house-fly kind, (Musca domestica,) and carefully measure them, or weigh them, we should find them all almost exactly of the same size; which, of course would not be the case if they really grew larger as they grew older.
But there are some insects which, after they leave their pupa, increase within a very short time to a size which could scarcely be believed. In particular, the new-born insects of a tribe of flies which produce the aphis-lion larva before spoken of, are distinguished by this peculiarity. We behold a very little insect emerge from the pupa-case, and in a quarter of an hour we are astonished to find it has grown to a great fly! This sudden increase appears the more marvellous, because during this period the insect takes no nourishment. The wings of this insect, when it is just born, are not more than one-tenth the size they acquire in that short space of time. The insect is to all appearance firm and plump, and offers a ridiculous contrast to the tiny pupa-case out of which it has emerged. It appears probable that this sudden enlargement is to be accounted for by the insect filling itself with air, and thus causing the various parts so closely packed together, and fitted into one another, in the pupa, to be expanded. The experiment which puts this idea to the test is a very simple one; we need only prick the body of the insect with a fine needle, and we shall hear a slight sound produced by the escape of the air; and in a few seconds the body of the creature shrinks to its former dimensions. It appears, indeed, that the body of the insect is actually larger at this time than at a subsequent period of its life, when it becomes more flattened and shorter. Another beautiful insect, one of the lace-winged flies, exhibits the same singular phenomenon. Its pupa-case is not larger than a small pea, yet the body of the insect is nearly half-an-inch long, and covers, when its wings and antennæ are expanded, a surface of an inch square. It appears, in fact, almost incredible that it could ever have been contained within so small a compass.
The cases just related may appear to be really exceptions to the rule just laid down, as to the non-increase of insects when once emerged from the pupa; but upon a little consideration it will be found that the exceptions are more apparent than real. The increase in size is not really a process of growth, but is simply owing to the expansion of the body of the insect to its due size, only taking place in a sudden manner by breathing a certain amount of air. The dragon-fly gives us another instance of a similar enlargement soon after leaving the pupa-case.
THE STRUCTURE AND ORGANS OF THE IMAGO.
White Hawthorn Butterfly.