224 OUR HOUSEHOLD INSECTS 



in the creatures, and that they can hardly be distin- 

 guished from insects with which we are familiar at 

 home. Nevertheless, it is a fact which we must con- 

 stantly bear in mind, that the insects to which these 

 names are applied are to all intents and purposes identical 

 both in structure and in life-history, and we are therefore 

 justified in making no distinction here. Moreover, there 

 is no doubt that, even in the matter of virulence, our 

 own gnats vary a good deal, both according to season 

 and to the temperament and sensitiveness of the person 

 attacke^. We must not, however, fail to note that there 

 are other flies, belonging to different families, that are 

 also blood-suckers, and in some cases are almost as trouble- 

 some as the true gnats and mosquitoes. This is specially 

 the case with the small flies called Simulice, which are 

 closely allied to the family CuUcidce, and are, it would 

 appear, sometimes called mosquitoes in America. Such 

 insects, however, are not referred to at present, and what 

 we have to say about " gnats and mosquitoes " concerns 

 only the family Culicidce, and, in fact, the genus Culex. 



Of the term "midges" it is somewhat more difficult 

 to fix the application ; it is indiscriminately used of at 

 least two types of flies, quite distinct from one another, 

 one, in most respects except persecuting powers, similar 

 to the gnats and mosquitoes, the other very different in 

 appearance, and at first sight more like tiny moths than 

 flies ; but it appears also to be popularly used in a loose 

 manner for small and annoying insects of whatever kind, 

 without any definite conception as to the actual form 

 intended. It is obvious, therefore, that when the ento- 

 mologist hears people talking vaguely of gnats and 

 midges, it is not always easy to understand exactly what 

 insects are being referred to. 



With these preliminary precautions, and bearing in 



