It is well known that mosquitoes, when they bite, inject into the wound a minute quantity of poison. The effect of this varies according to the species of mosquito and also depends very much on the susceptibility of the individual. Soon after the bite a sensation of itching is noticed and often a wheal, or eminence, is produced on the skin, which may increase to a considerable swelling. The scratching which is induced may cause a secondary infection and thus lead to serious results. Some people seem to acquire an immunity against the poison.
The purpose of this irritating fluid may be, as Reaumur suggested, to prevent the coagulation of the blood and thus not only to cause it to flow freely when the insect bites but to prevent its rapid coagulation in the stomach. Obviously, it is not developed as a protective fluid, and its presence subjects the group to the additional handicap of the vengeance of man.
As to the origin of the poison, there has been little question, until recent years, that it was a secretion from the salivary glands. Macloskie (1888) showed that each gland is subdivided into three lobes, the middle of which differs from the others in having evenly granulated contents and staining more deeply than the others.
(a) Normal position of the larvæ of Culex and Anopheles in the water. Culex, left; Anopheles, middle; Culex pupa, right hand figure
A flesh fly
In Milan the visitation of 1630 was credited to the so-called anointers,—men who were supposed to spread the plague by anointing the walls with magic ointment—and the most horrible tortures that human ingenuity could devise were imposed on scores of victims, regardless of `rank` or of public service. Manzoni's great historical novel, "The Betrothed" has well pictured conditions in Italy during this period.
he Diplopoda, or millipedes, are characterized by the presence of two pairs of legs to a segment. The largest of our local myriapods belong to this group. They live in moist places, feeding primarily on decaying vegetable matter, though a few species occasionally attack growing plants.
The millipedes are inoffensive and harmless. Julus terrestris, and related species, when irritated pour out over the entire body a yellowish secretion which escapes from cutaneous glands. It is volatile, with a pungent odor, and Phisalix (1900) has shown that it is an active poison when injected into the blood of experimental animals. This, however, does not entitle them to be considered as poisonous arthropods, in the sense of this chapter, any more than the toad can be considered poisonous to man because it secretes a venom from its cutaneous glands.
The Solpugida have long borne a bad reputation and, regarding virulence, have been classed with the scorpions. Among the effects of their bites have been described painful swelling, gangrene, loss of speech, cramps, delirium, unconsciousness and even death. Opposed to the numerous loose accounts of poisoning, there are a number of careful records by physicians and zoölogists which indicate clearly that the effects are local and though they may be severe, they show not the slightest symptom of direct poisoning.
The true scorpions are widely distributed throughout warm countries and everywhere bear an evil reputation. According to Comstock (1912), about a score of species occur in the Southern United States. These are comparatively small forms but in the tropics members of this group may reach a length of seven or eight inches. They are pre-eminently predaceous forms, which lie hidden during the day and seek their prey by night.
The scorpions possess large pedipalpi, terminated by strongly developed claws, or chelæ. They may be distinguished from all other Arachnids by the fact that the distinctly segmented abdomen is divided into a broad basal region of seven segments and a terminal, slender, tail-like division of five distinct segments
The tailed whip-scorpions, belonging to the family Thelyphonidæ, are represented in the United States by the giant whip-scorpion Mastigoproctus giganteus, which is common in Florida, Texas and some other parts of the South. In Florida, it is locally known as the "grampus" or "mule-killer" and is very greatly feared. There is no evidence that these fears have any foundation, and Dr. Marx states that there is neither a poison gland nor a pore in the claw of the chelicera.
The yellow fever mosquito breeds in cisterns, water barrels, pitchers and in the various water receptacles about the house. In our own Southern States it very commonly breeds in the above-ground cisterns which are in general use. Often the larvæ are found in flower vases, or even in the little cups of water which are placed under the legs of tables to prevent their being overrun by ants. They have been repeatedly found breeding in the holy water font in churches. In short, they breed in any collection of water in close proximity to the dwellings or gathering places of man.
n popular usage, the term "tarantula" is loosely applied to any one of a number of large spiders. The famous tarantulas of southern Europe, whose bites were supposed to cause the dancing mania, were Lycosidæ, or wolf-spiders. Though various species of this group were doubtless so designated, the one which seems to have been most implicated was Lycosa tarantula (L.). On the other hand, in this country, though there are many Lycosidæ, the term "tarantula" has been applied to members of the superfamily Avicularoidea, including the bird-spiders.
Anopheles crucians. Female
Anopheles punctipennis. Female
Anopheles quadrimaculatus mosquito, male and female
Until recently, the ticks attracted comparatively little attention from entomologists. Since their importance as carriers of disease has been established, interest in the group has been enormously stimulated and now they `rank` second only to the mosquitoes in the amount of detailed study that has been devoted to them.
The ticks are the largest of the Acarina. They are characterized by the fact that the hypostome, or "tongue" is large and file-like, roughened by sharp teeth.
Auchmeromyia luteola, the Congo floor maggot. This is a muscid of grewsome habits, which has a wide distribution throughout Africa. The fly deposits its eggs on the ground of the huts of the natives.
Several families of the true bugs include forms which, while normally inoffensive, are capable of inflicting painful wounds on man. In these, as in all of the Hemiptera, the mouth-parts are modified to form an organ for piercing and sucking.
The upper lip, or labrum, is much reduced and immovable, the lower lip, or labium, is elongated to form a jointed sheath, within which the lance-like mandibles and maxillæ are enclosed. The mandibles are more or less deeply serrated, depending on the species concerned.
Sepsis violacea; puparium and adult
The Simuliidæ, or black flies, are small, dark, or black flies, with a stout body and a hump-back appearance. The antennæ are short but eleven-segmented, the wings broad, without scales or hairs, and with the anterior veins stout but the others very weak. The mouth-parts are fitted for biting.
Airships, like aeroplanes, are being armed with guns and bombs; and their power of raising weights enables them to carry heavy weapons. Large and highly destructive bombs have been tested in the German airships, being released over the sea and aimed at targets in the form of rafts. Latest-type airships also carry guns in their cars; and the Zeppelins have a platform upon the tops of their hulls, reached by a ladder through the middle of the ship, from which a machine-gun can be fired upward. This is a very necessary precaution, and is intended to frustrate the attack of an aeroplane. It would be the aim of the latter, whenever possible, to manœuvre above its big enemy—as suggested in figure —and drop a bomb upon its hull. Hence the construction of the top platform of the airship, from which her gunners can direct a vigorous fire aloft.
...it was followed in due course by the use of small steam engines and electric motors, which were made to turn propellers such as are used in aeroplanes. For such experimental craft, the rounded form of gas-container was abandoned and a cigar-shaped envelope adopted, pointed at both ends, which could be more easily driven through the air. An airship of a crude and early type is seen here. It was built by an experimenter named Gifford, and in 1852 it flew at the rate of seven miles an hour.
A. Gas-containing envelope; B. Car suspended below envelope, which carried the aeronaut and a 3-horse-power steam engine; C. Two-bladed propeller driven by the engine; D. Rudder (in the form of a sail) by which the machine could be steered from side to side.