Our Common Insects Part 6



The subject of flies becomes of vast moment to a Pharaoh, whose ears are dinned with the buzz of myriad winged plagues, mingled with angry cries from malcontent and fly-pestered subjects; or to the summer traveller in northern lands, where they oppose a stronger barrier to his explorations than the loftiest mountains or the broadest streams; or to the African pioneer, whose cattle, his main dependence, are stung to death by the Tsetze fly; or the fariner whose eyes on the evening of a warm spring day, after a placid contemplation of his growing acres of wheat blades, suddenly detects in dismay clouds of the Wheat midge and Hessian fly hovering over their swaying tops. The subject, indeed, has in such cases a national importance, and a few words regarding the main points in the habits of flies--how they grow, how they do not grow (after assuming the winged state), and how they bite; for who has not endured the smart and sting of these dipterous Shylocks, that almost torment us out of our existence while taking their drop of our heart's blood--may be welcome to our readers.

[Illustration: 61. Head of the Mosquito.]

The Mosquito will be our first choice. As she leaps off from her light bark, the cast chrysalis skin of her early life beneath the waters, and sails away in the sunlight, her velvety wings fringed with silken hairs, and her neatly bodiced trim figure (though her nose is rather salient, considering that it is half as long as her entire body), present a beauty and grace of form and movement quite unsurpassed by her dipterous allies. She draws near and softly alights upon the hand of the charmed beholder, subdues her trumpeting notes, folds her wings noiselessly upon her back, daintily sets down one foot after the other, and with an eagerness chastened by the most refined delicacy for the feelings of her victim, and with the air of Velpeau redivivus, drives through crushed and bleeding capillaries, shrinking nerves and injured tissues, a many-bladed lancet of marvellous fineness, of wonderful complexity and fitness. While engorging herself with our blood, we will examine under the microscope the mosquito's mouth. The head (Fig. 61) is rounded, with the two eyes occupying a large part of the surface, and nearly meeting on the top of the head. Out of the forehead, so to speak, grow the long, delicate, hairy antennm (_a_), and just below arises the long beak which consists of the bristle-like maxillae (_mx_, with their palpi, _mp_) and mandibles (_m_), and the single hair-like labrum, these five bristle-like organs being laid in the hollowed labium (_l_). Thus massed into a single awl-like beak, the mosquito, without any apparent effort, thrusts them all except the labium into the flesh. Her hind body may be seen tilling with the red blood, until it cries quits, and the insect withdraws its sting and flies sluggishly away. In a moment the wounded parts itch slightly, though a very robust person may not notice the irritation, or a more delicate individual if asleep; though if weakened by disease, or if stung in a highly vascular and sensitive part, such as the eyelid, the bite becomes really a serious matter. Multiply the mosquito a thousand fold, and one flees their attacks and avoids their haunts as he would a nest of hornets. Early in spring the larva (Fig.

62, A) of the mosquito may be found in pools and ditches. It remains at the bottom feeding upon decaying matter (thus acting as a scavenger, and in this state doing great benefit in clearing swamps of miasms), until it rises to the surface for air, which it inhales through a single respiratory tube (_c_) situated near the tail. When about to transform into the pupa state, it contracts and enlarges anteriorly near the middle, the larval skin is thrown off, and the insect appears in quite a different form (Fig. 62, a). The head and thorax are massed together, the rudiments of the mouth parts and of the wings and legs being folded upon the breast, while there are two breathing tubes (_d_) situated upon the back instead of the tail, which ends in two broad paddles (_a_); so that it comes to the surface, head foremost instead of tail first, a position according better with its increased age and experience in pond life. In a few days the pupa skin is cast; the insect, availing itself of its old habiliments as a raft upon which to float while its body is drying, grows lighter, and its wings expand for its marriage flight. The males are beautiful, both physically and morally, as they do not bite; their manners are more retiring than those of their stronger minded partners, as they rarely enter our dwellings, and live unnoticed in the woods. They may be easily distinguished from the females by their long maxillary palpi, and their thick, bushy, feathered antennae. The female lays her elongated, oval eggs in a boat-shaped mass, which floats on the water. A mosquito lives three or four weeks in the water before changing to the adult or winged stage. How many days they live in the latter state we do not know.

[Illustration: 62. Larva and Pupa of the Mosquito.]

Our readers will understand, then, that all flies, like our mosquito for example, grow while in the larva and pupa state, _and after they acquire wings do not grow_, so that the small midges are not young mosquitoes, but the adult winged forms of an entirely different species and genus of fly; and the myriads of small flies, commonly supposed to be the young of larger flies, are adult forms belonging to different species of different genera, and perhaps of different families of the suborder of Diptera. The typical species of the genus Culex, to which the mosquito belongs, is Culex pipiens, described by Linnaeus, and there are already over thirty North American species of this genus described in various works. Few insects live in the sea, but along the coast of New England a small, slender white larva (Fig. 63a, magnified, and head greatly enlarged; Fig. 64, pupa and fore foot of larva, showing the hooks), whose body is no thicker than a knitting needle, lives between tides, and has even been dredged at a depth of over a hundred feet, which transforms into a yellow mosquito-like fly (Fig. 65, with head of the female, magnified) which swarms in summer in immense numbers. I have called it provisionally Chironomus oceanicus, or Ocean gnat. The larvae of other species have been found by Mr. S. I. Smith living at great depths in our Northern lakes. These kinds of gnats are usually seen early in spring hovering in swarms in mid air.

[Illustration: 65. Ocean Gnat.]

[Illustration: 63. Larva of Ocean Gnat.]

[Illustration: 64. Pupa of Ocean Gnat.]

The strange fact has been discovered by Grimm, a Russian naturalist, that the pupa of a feathered gnat is capable of laying eggs which produce young during the summer time. Previous to this it had been discovered that a larva of a gnat (Fig. 66 _a_, eggs from which the young are produced) which lives under the bark of trees in Europe, also produced young born alive.

The Hessian fly (Fig. 67, _a_, larva; _b_ pupa; _c_, stalk of wheat injured by larvae) and Wheat midge, which are allied to the mosquito, are briefly referred to in the calendar, so that we pass over these to consider another pest of our forests and prairies.

[Illustration: 66. Viviparous gall larva.]

[Illustration: 67. Hessian Fly and its Young.]

The Black fly is even a more formidable pest than the mosquito. In the northern, subarctic regions, it opposes a barrier against travel. The Labrador fisherman spends his summer on the sea shore, scarcely daring to penetrate the interior on account of the swarms of these flies.

During a summer residence on this coast, we sailed up the Esquimaux river for six or eight miles, spending a few hours at a house situated on the bank. The day was warm and but little wind blowing, and the swarms of black flies were absolutely terrific. In vain we frantically waved our net among them, allured by some rare moth; after making a few desperate charges in the face of the thronging pests, we had to retire to the house, where the windows actually swarmed with them; but here they would fly in our faces, crawl under one's clothes, where they even remain and bite in the night. The children in the house were sickly and worn by their unceasing torments; and the shaggy Newfoundland dogs whose thick coats would seem to be proof against their bites ran from their shelter beneath the bench and dashed into the river, their only retreat.

In cloudy weather, unlike the mosquito, the black fly disappears, only flying when the sun shines. The bite of the black fly is often severe, the creature leaving a large clot of blood to mark the scene of its surgical triumphs. Prof. E. T. Cox, State Geologist of Indiana, has sent us specimens of a much larger fly, which Baron Osten Sacken refers to this genus, which is called on the prairies, where it is said to bite horses to death, the Buffalo Gnat. Westwood states that an allied fly (Rhagio Columbaschensis) is one of the greatest scourges of man and beast in Hungary, where it has been known to kill cattle.

[Illustration: 68. Black fly.]

[Illustration: 69. Black Fly Larva.]

The Simulium molestum (Fig. 68, enlarged), as the black fly is called, lives during the larva state in the water. The larva of a Labrador species (Fig. 69, enlarged) which we found, is about a quarter of an inch long, and of the appearance here indicated. The pupa is also aquatic, having long respiratory filaments attached to each side of the front of the thorax. According to Westwood, "the posterior part of its body is enclosed in a semioval membranous cocoon, which is at first formed by the larva, the anterior part of which is eaten away before changing to a pupa, so as to be open in front. The imago is produced beneath the surface of the water, its fine silky covering serving to repel the action of the water."

[Illustration: 70. Mycetobia.]

Multitudes of a long, slender, white worm may often be found living in the dirt, and sour sap running from wounds in the elm tree. Two summers ago we discovered some of these larvae, and on rearing them found that they were a species of Mycetobia (Fig. 70; _a_, larva; _b_, pupa). The larva is remarkable for having the abdominal segments divided into two portions, the hinder much smaller than the anterior division. Its whole length is a little over a third of an inch. The pupae were found sticking out in considerable numbers from the tree, being anchored by the little spines at the tail. The head is square, ending in two horns, and the body is straight and covered with spines, especially towards the end of the tail. They were a fifth of an inch in length. The last of June the flies appeared, somewhat resembling gnats, and about a line long. The worms continued to infest the tree for six weeks, the flies remaining either upon or near it.

[Illustration: 71. Mouth Parts of Tabanus.]

We now come to that terror of our equine friends, the Horse fly, Gad, or Breeze fly. In its larval state, some species live in water, and in damp places under stones and pieces of wood, and others in the earth away from water, where they feed on animal, and, probably, on decaying matter. Mr. B. D. Walsh found an aquatic larva of this genus, which, within a short time, devoured eleven water snails. Thus at this stage of existence, this fly, often so destructive, even at times killing our horses, is beneficial. During the hotter parts of summer, and when the sun is shining brightly, thousands of these Horse flies appear on our marshes and inland prairies. There are many different kinds, over one hundred species of the genus Tabanus alone, living in North America. Our most common species is the "Green head," or Tabanus lineola. When about to bite, it settles quietly down upon the hand, face or foot, it matters not which, and thrusts its formidable lancet-like jaws deep into the flesh. Its bite is very painful, as we can testify from personal experience. We were told during the last summer that a horse, which stood fastened to a tree in a field near the marshes at Rowley, Mass., was bitten to death by these Green heads; and it is known that horses and cattle are occasionally killed by their repeated harassing bites. In cloudy weather they do not fly, and they perish on the cool frosty nights of September. The Timb, or Tsetze fly, is a species of this group of flies, and while it does not attack man, plagues to death, and is said to poison by its bite, the cattle in certain districts of the interior of Africa, thus almost barring out explorers. On comparing the mouth-parts of the Horse fly (Fig. 71, mouth of T. lineola), we have all the parts seen in the mosquito, but greatly modified. Like the mosquito, the females alone bite, the male Horse fly being harmless, and frequenting flowers, living upon their sweets. The labrum (_lb_), mandibles (_m_) and maxillae (_mx_), are short, stiff and lancet-like, and the maxillary palpi (_mp_; _a_, the five terminal joints of the antennae) are large, stout, and two-jointed. While the jaws (both maxillae and mandibles) are thrust into the flesh, the tongue (_l_) spreads around the tube thus formed by the lancets, and pumps up the blood flowing from the wound, by aid of the sucking stomach, or crop, being a sac appended to the throat. Other Gad flies, but much smaller, though as annoying to us in woods and fields, are the species of Golden eyed flies, Chrysops, which fly and buzz interminably about our ears, often taking a sudden nip. They plague cattle, settling upon them and drawing their blood at their leisure.

[Illustration: 72. Carpet Fly.]

[Illustration: 73. Carpet Worm.]

We turn to a comparatively unknown insect, which has occasionally excited some distrust in the minds of housekeepers. It is the carpet fly, Scenopinus pallipes (Fig. 72), which, in the larva state, is found under carpets, on which it is said to feed. The worm (Fig. 73) has a long, white, cylindrical body, divided into twelve segments, exclusive of the head, while the first eight abdominal segments are divided by a transverse suture, so that there appear to be seventeen abdominal segments, the sutures appearing too distinct in the cut. Mr. F. G.

Sanborn has reared the fly, here figured, from the worm. The larva also lives in rotten wood; it is too scarce ever to prove very destructive in houses. Either this or a similar fly was once found, we are told by a scientific friend, in great numbers in a "rat" used in dressing a young lady's hair; the worms were living upon the hair stuffing.

One of the most puzzling objects to the collector of shells or insects, is the almost spherical larva of Microdon globosus (Fig. 74). It is flattened and smooth beneath and seems to adhere to the under side of stones, where it might be mistaken for a snail.

The Syrphus fly, or Aphis eater, deserves more than the passing notice which we bestow upon it. The maggot (Fig. 75, in the act of devouring an Aphis) is to be sought for established in a group of plant lice (Aphis), which it seizes by means of the long extensible front part of the body.

The adult fly (Fig. 76) is gayly spotted and banded with yellow, resembling closely a wasp. It frequents flowers.

[Illustration: 74. Microdon.]

[Illustration: 75. Syrphus Larva.] 76. Syrphus Fly.]

[Illustration: 77. Larva of Rat-tailed Fly. 78. Rat-tailed Fly and its Pupa.]

The singular rat-tailed pupa-case of Eristalis (Fig. 77) lives in water, and when in want of air, protrudes its long respiratory tube out into the air. We present the figure of an allied fly, Merodon Bardus (Fig.

78; _a_, puparium, natural size). We will not describe at length the fly, as the admirable drawings of Mr. Emerton cannot fail to render it easily recognizable. The larva is much like the puparium or pupa case, here figured, which closely resembles that of Eristalis, in possessing along respiratory filament, showing that the maggot undoubtedly lives in the water, and when desirous of breathing, protrudes the tube out of the water, thus drawing in air enough to fill its internal respiratory tubes (tracheae). The Merodon Narcissa probably lives in the soil, or in rotten wood, as the pupa-case has no respiratory tube, having instead a very short, sessile, truncated tube, scarcely as long as it is thick. The case itself is cylindrical, and rounded alike at each end.

[Illustration: 79. Human Bot Worm.]

We now come to the Bot flies, which are among the most extraordinary, in their habits, of all insects. The history of the Bot flies is in brief thus. The adult two-winged fly lays its eggs on the exterior of the animal to be infested. They are conveyed into the interior of the host, where they hatch, and the worm or maggot lives by sucking in the purulent matter, caused by the irritation set up by its presence in its host; or else the worm itself, after hatching, bores under the skin.

When fully grown, it quits the body and finishes its transformations to the fly-state under ground. Many quadrupeds, from mice, squirrels, and rabbits, up to the ox, horse, and even the rhinoceros, suffer from their attacks, while man himself is not exempt. The body of the adult fly is stout and hairy, and it is easily recognized by having the opening of the mouth very small, the mouth-parts being very rudimentary. The larvae are, in general, thick, fleshy, footless grubs, consisting of eleven segments, exclusive of the head, which are covered with rows of spines and tubercles, by which they move about within the body, thus irritating the animals in which they take up their abode. The breathing pores (stigmata) open in a scaly plate at the posterior end of the body. The mouth-parts (mandibles, etc.) of the subcutaneous larvae consist of fleshy tubercles, while in those species which live in the stomachs and frontal sinuses of their host, they are armed with horny hooks.

[Illustration: 80. Horse Bot Fly.]

The larvae attain their full size after moulting twice. Just before assuming the pupa state, the maggot leaves its peculiar dwelling place, descends into the ground and there becomes a pupa, though retaining its larval skin, which serves as a protection to it, whence it is called a "puparium."

Several well-authenticated instances are on record of a species of bot fly inhabiting the body of man, in Central and South America, producing painful tumors under the skin of the arm, legs and abdomen. It is still under dispute whether this human bot fly is a true or accidental parasite, the more probable opinion being that its proper host is the monkey or dog. In Cayenne, this revolting grub is called the Ver macaque (Fig. 79); in Para, Ura; in Costa Rica, Torcel; and in New Granada, Gusano peludo, or Nuche. The Dermatobia noxialis, supposed to be the Ver moyocuil of the inhabitants of Mexico and New Granada, lives beneath the skin of the dog.

[Illustration: 81. Bot Fly of Ox, and Larva.]

[Illustration: 82. Sheep Bot.]

[Illustration: 83. Skin Bot Fly.]

The Bot fly of the horse, (Gastrophilus equi, Fig. 80 and larva), is pale yellowish, spotted with red, with short, grayish, yellow hairs, and the wings are banded with reddish. She lays her eggs upon the knees of the horse. They are conveyed into the stomach, where the larva lives from May until October, and when full grown are found hanging by their mouth hooks on the edge of the rectum of the horse, whence they are carried out in the excrement. The pupa state lasts for thirty or forty days, and the perfect fly appears the next season, from June until October.

The Bot fly of the ox (Hypoderma bovis, Fig. 81, and larva), is black and densely hairy, and the thorax is banded with yellow and white. The larva is found during the month of May, and also in summer, living in tumors on the backs of cattle. When fully grown, which is generally in July, they make their way out and fall to the ground, and live in the pupa-case from twenty-six to thirty days, the fly appearing from May until September. It is found all over the world. The Oestrus ovis, or sheep Bot fly (Fig. 82, larva), is of a dirty ash color. The abdomen is marbled with yellowish and white flecks, and is hairy at the end. This species of Bot fly is larviparous, i.e., the eggs are hatched within the body of the mother, the larvae being produced alive. M. F. Brauer, of Vienna, the author of the most thorough work we have on these flies, tells me that he knows of but one other Bot fly (a species of Cephanomyia) which produces living larvae instead of eggs. The eggs of certain other species of Bot flies do not hatch until three or four days after they are laid. The larvae of the sheep Bot fly live, during April, May and June, in the frontal sinus of the sheep, and also in the nasal cavity, whence they fall to the ground when fully grown. In twenty-four hours they change to pupae, and the flies appear during the summer.

We also figure the Cuterebra buccata (Fig. 83; _a_, side view,) which resembles in the larval state the ox Bot fly. Its habits are not known, though the young of other species infest the opossum, squirrel, hare, etc., living in subcutaneous tumors.

[Illustration: The banded Lithacodes.]


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