872 AN INTRODUCTION TO ENTOMOLOGY 



('97). The manner in which the larva finds its way into the body of 

 its host differs greatly in different species of tachinids. Many obser- 

 vations on this have been made at the Gipsy Moth Laboratory and re- 

 ported by Townsend ('08 b). In many species the female fastens 

 her eggs to the skin of the caterpillar (Fig. 11 17); when the larvas 

 hatch they bore their way into their host and live there till they are 

 full-grown. In some of the viviparous species the female punctures 

 the skin of the caterpillar with the sheath of her ovipositor and de- 

 posits the larva within the body of the host. Some species deposit 

 their eggs on the leaves of the food-plant of their host; these eggs are 

 swallowed when the leaves are eaten. But most remarkable of all is 

 the method practiced by Eupeleteria magnicornis; this is a viviparous 

 species which infests the larva of the brown-tail moth. It attaches 

 its larvae to the surface of stems and leaves by a thin membranous 

 case, which is cup-shaped and surrounds the anal end of the larva. 

 Attached to the stem or leaf by this base, the maggot is able to reach 

 out in all directions as far as its length will permit. As the maggot 

 is deposited on the silken thread with which the caterpillar marks 

 its trail as it leaves its nest, it is in a position where it can attach itself 

 to the caterpillar when it is on its way back to the nest. 



Family MUSCID^ 

 The Typical Muscids 



To this family belong the house-fly and many other well-known 

 members of the Muscoidea. In this family either the hypopleural 

 or the pteropleural bristles are present, the basal bristles of the ab- 

 domen are reduced, and the arista of the antennae are plumose to the 

 tip. Among the more important species are the following. 



The house-fly or typhoid-fly, Musca domestica. — This is the most 

 familiar representative of the order Diptera, as it abounds in oiu- 

 dwellings. The flies lay their eggs preferably on horse-manure, but 

 will oviposit on other decaying vegetable matter, when horse-manure 

 is not available. A single female may deposit from 120 to 160 eggs 

 at one laying, and they have been observed to make as many as four 

 layings. The larvas become full-grown in from five to seven days; 

 the pupa state lasts from five to seven days; and in about fourteen 

 days after the flies emerge they are ready to oviposit. Hence there 

 may be at least a generation a month during the warm season ; and 

 from a few overwintering flies an immense ntmiber may be developed. 

 The house-fly is not only an exceedingly annoying pest in our dwel- 

 lings, but as it will breed in human excrement, especially where there 

 are open closets, it is doubtless often a carrier of the germs of typhoid 

 fever, dysentery, and other enteric diseases. For these reasons Dr. 

 Howard has suggested that this species be known as the typhoid-fly 

 and the "Swat-the-fly" crusades have been urged. Various means of 

 protection from this pest, as window-screens and different kinds of 

 traps, are well-known; but as Howard has so well put it, "the truest 



