[Regent's Park.
RAT-TAILED LARVA.
Common in filthy water.
Respecting mosquitoes in South America, Mr. H. W. Bates writes, in his work "The Naturalist on the Amazons," when passing a night in a boat about twenty-five miles from the town of Villa Nova: "At night it was quite impossible to sleep for mosquitoes; they fell upon us by myriads, and without much piping came straight at our faces as thick as rain-drops in a shower. The men crowded into the cabins, and then tried to expel the pests by the smoke from burnt rags; but it was of little avail, although we were half suffocated during the operation." But the sand-flies, encountered a little higher up the river, were much worse: "We made acquaintance on this coast with a new insect-pest, the Piúm, a minute fly, two-thirds of a line in length, which here commences its reign, and continues henceforward as a terrible scourge along the upper river, or Solimoens, to the end of the navigation on the Amazons. It comes forth only by day, relieving the mosquito at sunrise with the greatest punctuality, and occurs only near the muddy shores of the stream, not one ever being found in the shade of the forest. In places where it is abundant, it accompanies canoes in such dense swarms as to resemble thin clouds of smoke. It made its appearance in this way the first day after we crossed the river. Before I was aware of the presence of flies, I felt a slight itching on my neck, wrist, and ankles, and, on looking for the cause, saw a number of tiny objects, having a disgusting resemblance to lice, adhering to the skin. This was my first introduction to the much-talked-of Piúm. On close examination, they are seen to be small two-winged insects, with dark-coloured body and pale legs and wings, the latter closed lengthwise over the back. They alight imperceptibly, and, squatting close, fall at once to work, stretching forward their tiny front legs, which are in constant motion, and seem to act as feelers, and then applying their short, broad snouts to the skin. Their abdomens soon become distended and red with blood, and then, their thirst satisfied, they soon move off, sometimes so stupefied with their potations that they can scarcely fly. No pain is felt whilst they are at work, but they each leave a small circular raised spot on the skin, and a disagreeable irritation. The latter may be avoided in great measure by pressing out the blood which remains in the spot; but this is a troublesome task when one has several hundred punctures in the course of a day [like Prince Siror, in one of Bulwer Lytton's stories, who fell "pierced by five hundred spears">[. I took the trouble to dissect specimens, to ascertain the way in which the little pests operate. The mouth consists of a pair of thick fleshy lips, and two triangular horny lancets, answering to the upper lip and tongue of other insects. This is applied closely to the skin, a puncture is made with the lancets, and the blood then sucked through between these into the œsophagus, the circular spot which results coinciding with the shape of the lips. In the course of a few days the red spots dry up, and the skin in time becomes blackened with the endless number of discoloured punctures that are crowded together. The irritation they produce is more acutely felt by some persons than others. I once travelled with a middle-aged Portuguese who was laid up for three weeks from the attacks of Piúm, his legs being swelled to an enormous size, and the punctures aggravated into spreading sores."
Photo by by W. P. Dando, F.Z.S., Regent's Park.
HOUSE-FLY (MALE AND FEMALE).
The larvæ of the house-fly live in refuse, so do not thrive where cleanliness abounds.
However, the traveller in Amazonia has one consolation: the great rivers which traverse the forests are of three different colours; and the black-water rivers—so called from the dark colour of the water, owing apparently to the amount of vegetable matter which they hold in solution—are never infested with mosquitoes. Probably the character of the water renders it unsuitable to them for breeding purposes.
The Crane-flies, or Daddy-long-legs, are also very injurious insects, but in a different manner, for their subterranean maggots feed on and destroy the roots of grass in the same way as the grubs of the Cockchafers. They are insects of considerable size, with slender bodies, terminating in a short, horny point (the ovipositor) in the female, and with long, slender legs, which are liable to break off at the least touch. The commonest species has a grey body and transparent wings; but there is a larger one with the wings prettily variegated with brown, and a smaller one in which there are yellow markings towards the end of the body.