LITTLE BLUE BOOK NO. 860 Edited by E. Haldeman-Julius
Our Insect Enemies
Vance Randolph
Drawings by Peter Quinn
HALDEMAN-JULIUS COMPANY GIRARD, KANSAS
Copyrighted, 1925, Haldeman-Julius Company
CONTENTS
Page
Houseflies and Their Kindred 4
Mosquitoes and Disease 28
Life Among the Bedbugs 43
Lice, Crabs and Cooties 47
Our Friend the Cockroach 54
Chiggers, Ticks and Fleas 57
PRINTED IN THE UNITED STATES OF AMERICA
LIST OF ILLUSTRATIONS
Page
Fig. I. The Metamorphosis of the Housefly (Musca domestica). 12
Fig. II. Malaria and its Carrier. 33
Fig. III. Three kinds of Lice. 51
Fig. IV. Some Common Cockroaches. 58
Fig. V. Chiggers and Ticks. 61
OUR INSECT ENEMIES
HOUSEFLIES AND THEIR KINDRED
The common housefly (Musca domestica) is perhaps more thoroughly domesticated than any other insect; it lives and flourishes wherever man has established his settlements, and does not thrive elsewhere. It is mentioned by many of the ancient writers, and has evidently been associated with man from the remotest antiquity, doubtless adapting itself gradually to his changing modes of life. It still breeds in the refuse which accumulates about his buildings, and still invades his home to partake of his food. When one considers the number of flies which get into modern dwellings despite glass and wire and modern insecticides, it is difficult to understand how our sturdy fathers managed to survive the summers in mediaeval Europe. Picture Thomas Aquinas battling with swarms of flies for his food! The housefly’s favorite breeding place has always been in horse manure, and man has until recent years had great quantities of this nutritious substance about him; with the coming of the automobile this condition has been changed somewhat, but even the cleanest of American cities still affords sufficient decaying matter to assure a bountiful crop of flies. At some future day perhaps we shall have cities so spotless that there will be nowhere a speck of garbage large enough to nourish a maggot, but that day is still to come, and it doth not yet appear what we shall be.
Meanwhile, as Herrick says, the housefly is with us always. “They are present from early spring to late fall, even remaining far into the winter. They are troublesome in kitchens and dining rooms because of their abundance, their proneness to get into food, and their generally filthy habits. Until recent years the housefly has been generally regarded as somewhat of a scavenger and has been considered of value to humanity because of its aid in the removal of wastes that are a menace to human welfare. The eggs of the housefly are often deposited on decaying vegetable matter that is allowed to accumulate in the vicinity of human habitations and the maggots that hatch from the eggs live on this decaying matter and aid in destroying it. Thus it must be conceded, perhaps, that houseflies do assist somewhat in the removal of foul and dangerous waste matters and, to this extent, are of benefit. On the other hand, it has been conclusively shown that this modicum of benefit is greatly overbalanced by their role in disseminating dangerous diseases. It has been shown that houseflies carry the germs of cholera, typhoid fever, cholera infantum, and tropical dysentery on their feet, legs, bodies and in their digestive tracts. There can be no doubt of the responsibility of the housefly for much sickness and many deaths.”
Although the adult housefly is equally fond of fresh and putrid matter, flitting from filth to food and back again, the eggs are always laid in decaying substances, preferably horse manure. In the absence of this delicacy the eggs may be deposited in human excrement, or even cow manure if it is not too dry. A single female fly often deposits one hundred and fifty eggs at a single sitting, and lays as many as six or seven hundred in the course of a season.
The egg is white and shaped like a grain of wheat; it measures about one-twentieth of an inch in length, and hatches in from ten to twenty-four hours, the period of incubation varying with the temperature. The second or larval stage is represented by a wormlike creature called a maggot, which crawls about and devours great quantities of nourishing manure. When the maggot is about five or six days old it has attained a length of nearly three-eighths of an inch, and transforms into the pupa; it is no longer active, ceases to take food, and the outer skin turns into a hard, brown, dry case called a puparium. After five or six days of rest the puparium is burst open and the adult fly crawls out.
The newly emerged flies mate within two or three days, and the young females are soon laying their first batch of eggs. Thus the whole development may occur in about fourteen days, and Herrick thinks that in Washington, D. C., it may be complete in ten days or less, according to the temperature, with ten or twelve generations in a summer. “One can hardly realize,” says Herrick, “the enormous numbers that such rapid development is capable of producing. Inside of two months, one female fly can give rise to many millions of progeny. For the purpose of illustration, we will assume that a female fly lays 100 eggs. If these hatch and all the larvae come to maturity, about one-half will probably be males and the other half females. Then at the end of the first generation there will be fifty egg-laying females. At this rate, at the end of the eighth generation there would be produced about 1,875,000,000,000 adults. Of course, in nature, a very large part of these would die before reaching maturity, so that actually one female would probably never produce such an enormous number of individuals. However, even under normal conditions tremendous numbers are produced.”
The adult housefly is unhappily too familiar to require a lengthy description. The total length is about one-fourth of an inch, there are two membranous wings and six hairy legs, while the thorax is gray with four dark longitudinal stripes above. Besides the hairs and bristles on the body and legs, which entangle great numbers of germs, the sticky pulvilli of the feet gather bacteria as if they had been especially developed for that purpose. Thus every housefly scatters bacteria broadcast wherever he goes; one has only to allow a fly to walk across a plate of sterile gelatin to see large colonies of bacteria produced in every foot-print. Esten and Mason’s examination of some 400 specimens showed that the number of bacteria carried ranged from 550 to 6,600,000 per fly, with an average of nearly a million and a quarter.
The general impression is that the housefly does not travel any great distance from its birth-place, but there is considerable doubt about this matter. Hewitt has taken them flying at least eighty feet above the ground, and it is obvious that small insects which rise so high may be carried long distances by the wind. Copeman, Howlett and Merriman have attacked the problem by marking large numbers of specimens, releasing them, and then watching for them in traps set at various distances; they recovered several which had travelled more than three-fourths of a mile. Dr. Hodge found plenty of houseflies on the cribs of the Cleveland waterworks, which are located six miles out in Lake Erie, and which offer no breeding places for flies. He naturally concluded that they were blown six miles by the wind.
It has been pretty well established that adult flies do not retain and disseminate disease germs which they swallowed as maggots in the manure, but only those which they acquire in the adult state. It has been definitely proved, however, that the bacilli of typhoid fever are carried on the bodies and legs of houseflies, and also that the bacilli are often swallowed and survive the passage through the body, as living bacilli have frequently been demonstrated in flyspecks. The most important practical consideration is, of course, the actual frequency with which houseflies do transfer pathogenic organisms from filth to food intended for human consumption, thus spreading disease, and this is in its very nature a difficult matter to investigate.
Typhoid fever is a disease affecting the intestines, and the bacilli which cause it frequently remain in the body for long periods after the patient has apparently recovered. The germs are passed out in the urine and fecal matter. As Herrick puts it: “If the excreta or urine containing these bacilli are deposited where they are accessible to flies, for instance in open privies, the chances are high that the bacilli will be carried on the bodies of these insects back to the kitchens and dining rooms and be deposited on our food. During the Spanish-American War, flies were traced by their whitened feet from the lime-sprinkled, open latrines or privies to the dining tables of the soldiers in camp. It makes one shudder to think of the thousands of open closets in the small towns of the United States to which flies have access and in which they breed and from which they may come direct to our kitchens and dining rooms.”