The True Flies 



See the bedbug among the Heteroptera, the true lice (Anoplura) 

 and the bird lice (Mallophaga). With those species which lay eggs 

 the larval development is usually rapid; and with some forms, 

 particularly those which are true scavengers and feeders upon 

 carrion or upon excrement, it becomes very rapid. The possi- 

 bilities for enormous multiplication are apparently greater in this 

 order than in any other group of insects. It is estimated that the 

 progeny of a single house-fly, if undisturbed, would in the course 

 of a single summer reach high into the billions in numbers, while 

 an almost equally rapid multiplication takes place with some of 

 the mosquitoes. 



There is great variation in habits in the group. Most flies 

 prefer the sunshine and are most numerous in the middle of sunny 

 days. A few, however, such as the mosquitoes, fly at night. 

 These, however, are the great exception. Very many flies 

 frequent flowers, and thus exercise a beneficial function in the 

 cross-fertilization of plants. Many species — comprising, in fact, 

 whole families — are aquatic or sub-aquatic in their early stages, 

 and some possess the faculty of living under what appear to be 

 most disadvantageous conditions. Some of the flies of the 

 peculiar family Ephydridae, for example, live in the strongly 

 alkaline lakes of the far West where almost nothing else can live. 



It is surprising how little of an intimate and exact nature is 

 known concerning the life history of most flies. It is true that 

 maggots are not attractive creatures, but the mode of life is so 

 variable in the different groups of flies and the transformations are 

 so remarkable that a very great interest attaches to many of these 

 life histories. Unfortunately, however, very few observers have 

 done any work in this direction and it results that there is room 

 for an army of workers who will find it especially easy in this 

 order to add to scientific knowledge. It will be noticed in the 

 consideration which follows of the different families that full ob- 

 servations have not yet been recorded in many of them from 

 which typical life histories can be drawn up. This is a sad state 

 of affairs and it is one which observers of nature should endeavor 

 to remedy. As an example, it was not until 1895 that a full ac- 

 count was published of a single one of our common North Ameri- 

 can mosquitoes and even so ubiquitous an insect as the house-fly 

 was neglected in this country until a comparatively recent date. 

 It is a strange fact, although not impossible to explain, that our com- 



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