THE YOUNG 



NATURALIST. 



35 



some respects, that he at once decides it to 

 be a variety ; and as varieties are compara- 

 tively numerous in some very common 

 i insects, such as caja and grossulariata, he is 

 I not unlikely to make acquaintance with 

 I them very early in his career, But while 

 his attention has been confined to his own 

 collection he is not likely to learn anything 

 of what I am calling local races. Species 

 he cannot obtain at home he gets by ex- 

 i change from another collector or purchase 

 I from a dealer, but he is not likely to notice, 

 in the few specimens he preserves as his 

 "series," that there is any constant varia- 

 tion in examples from different localities. 



It is probable that no two animals of any 

 species ever resembled each other in every 

 particular. We are used daily to see the 

 human form and face, and even when the 

 form is concealed by loose draperies, our 

 1 eyes are so educated as to recognise 

 individuals at a little distance without 

 seeing the face at all. The shepherd can 

 ! recognise any one of his sheep. The pigeon 

 fancier knows his individual birds, even 

 when all of one kind and colour. The 

 uneducated eye cannot do this, and we are 

 apt to conclude that a species does not vary 

 because we are unable to notice the variation. 

 But while there is little doubt that all 

 species vary, some in greater degree than 

 others, there is equally little doubt that the 

 parent form has a tendency to produce 

 1 offspring of like character. The operation 

 then of these two tendencies, — the tendency 

 of species to vary, and the tendency of 

 parents to produce offspring like themselves, 

 i leads to the formation of Local Races when 

 • any Local circumstance tends to the 

 preservation of a darker, lighter or otherwise 

 altered form. An insect that rests on the 

 ground will have a better chance of escape 

 from insectivorous birds, &c, the more 

 nearly it resembles in hue, the colour of the 

 ground it sits on. Thus the darkest speci- 

 mens would be best preserved on dark soil, 



they would produce darker offspring, and 

 gradually the whole race would become 

 darker. So on light soil paler specimens 

 would be less easily noticed, would tend to 

 produce paler offspring and gradually the 

 entire race would become lighter. If this 

 occur with an entire species it would 

 probably escape notice, but when it 

 only occurs in one place, the change is 

 necessarily observed so soon as specimens 

 from two different localities are placed side 

 by side in the cabinet. One well known 

 illustration may be given here. The Annulet 

 (Gnophos pullata) sits on the ground, it is 

 dark coloured in Perthshire and in the 

 New Forest, on peat ; pale in the chalk 

 districts; yellowish brown on clay, &c 

 Of this species there are several well 

 defined Local Races, and beginners will 

 have no difficulty in obtaining some of 

 them, and they will then understand what 

 is meant by the term. But while a case of 

 this kind can be easily explained, there are 

 many other forms of variation the cause of 

 which we do not yet know, or can only 

 vaguely guess at. The subject, however, is 

 so large that it will be best divided, and 

 each part considered separately. 



I would class all departures from the 

 normal type into three classes. Monstrosi- 

 ties, Aberrations, and Varieties. I will 

 attempt to deal with them in this order, the 

 last being the most important. 



Monstrosities. 



Under this head I would place all those 

 specimens that differ otherwise than in their 

 wing markings from the normal form. 

 Insects have occurred in the perfect state, 

 with the larval head yet unchanged. Some 

 in which the antennas of the sexes differ, 

 are occasionally found with the antennae on 

 one side resembling that ot the male, and 

 on the other side that of the female.— Where 

 the wings as well as antennae differ, this 

 same peculiarity sometimes extends to the 

 wings, and on one side they will present the 



