Introduction. xxv 



Diseases. — 'L.diivx: are subject to many diseases, among which is diarrhoea, which destroys 

 great numbers. They are also subject to a kind of low fever, and to the attacks of fungi and other 

 low vegetable parasites. Sick larvae are generally sluggish, flabby, and sometimes discoloured with 

 spots or blotches. Many are also destroyed by vicissitudes of the seasons, especially when moulting, 

 which is always a critical period. A continuance of cold wet weather in spring is peculiarly fatal 

 to them ; on the other hand, larvae and pups bear the cold of winter very well. During Ross's 

 second Arctic Expedition several larvae were collected, which revived at once when brought into 

 the cabin, though previously frozen so stiff that some of them had been snapped like glass. 



SYSTEMATIC REMARKS. 



Species, Variety, Aberration. — A species is an assemblage of individuals, consisting of two 

 sexes, male and female, which pair, and produce offspring similar to themselves. But the 

 individuals of the same species vary within certain limits, independently of the ordinary sexual 

 differences, in size, colour, markings, and outline, without ceasing to be recognised as belonging 

 to it. All these differences, when unimportant, are classed under the idea of the typical form of 

 the species. But we meet with other variations which are more unlike the usual form, and are 

 often quite dissimilar. When these appear occasionally in single individuals among those of the 

 typical form, they are called aberrations ; but when they are of frequent occurrence, they are 

 called varieties. . These are often confined to special localities, as when we find a dark form of 

 a species on mountains or in a more northerly locality, while those found on the plains or further 

 south are brighter coloured. Such forms are called local varieties ; and when they are both 

 peculiarly well marked, and also isolated, as is the case with many insects which are peculiar to 

 Corsica and Sardinia, they may justly be termed sub-species. Lastly, when two different forms 

 of the same insect appear at different times of the year, the phenomenon is called seasonal 

 dimorphism, and the varieties are called broods. 



Hybrids. — It sometimes happens that nearly allied, though truly distinct species pair, and 

 produce offspring which resemble neither of their parents, but combine the characters of both 

 species in varying proportions. It is more than doubtful whether these varieties can perpetuate 

 themselves ; and, in many cases, the resulting insects are hermaphrodites, in which the sexes are 

 mi.xed as well as the species. Many broods of hybrids die in the larva state, and most of those 

 known were bred in confinement. A true hybrid is very rarely produced in a state of nature. 



Classification. — An assemblage of species which agree in certain peculiarities which are 

 exclusively confined to them in the same combination, forms a genus. The name of a 

 species is composed of the name of the species combined with that of the genus. Allied 

 genera are classed in families, and families are again combined in groups. 



The characters of the genera and families are chiefly taken from the antenna, palpi, legs, and 

 wings, and the arrangement of the nervures of the wings is also of considerable importance. 



Linnaeus divided the Lepidoptcra into three genera only : Papilio, Sphinx, and Plialcena, or 

 Butterflies, Hawk Moths, and Moths. He sub-divided Phalirna into Attaeiis, Bouibyx, Noctica, 

 Geoinetra, Pyralis, Tortri.v, Tinea, and Alucita. These sections were again sub-divided bj' later 

 authors, and various modifications proposed ; but the classification of the Lepidoptera is an 

 exceedingly difficult study, and we have none which can be considered quite satisfactory at 

 present. It would be out of place to enter into the various systems of classification in detail 

 in an elementary work like this ; and the classification which we have adopted is based upon 

 the system of Herrich-Schaffer, with some modifications by Lederer, Speyer, and others. The 

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