THE YOUNG 



NATURALIST 



65 



may be going on, and that the band is being 

 gradually acquired, rather than gradually 

 lost. This is so evident that it does 

 not seem necessary to argue the point. 

 Change must produce change, not uni- 

 formity. The band then being derived from 

 a common ancestor, has already been 

 eliminated from the wings of many species, 

 and is gradually disappearing from others. 

 When this band, or traces of it, appear on 

 the wings of a bandless species, or when it 

 is more clearly defined than on the ordinary 

 form of one from which it has not yet dis- 

 appeared, such change is due to Reversion. 

 When the variety shows change in the 

 opposite direction — the bar broken, paler in 

 one portion, not so distinctly outlined, or 

 otherwise less clearly defined — it is a for- 

 ward change, and might be called an 

 example of Progresion. 



I think it will be found that these two 

 classes of varieties will absorb a large 

 number of specimens. I have confined my 

 remarks and illustrations to the one subject 

 of the band in the Geometrce, but the 

 changes going on are not confined to one 

 particular marking, or even to the markings 

 themselves. All parts of the insect, as of 

 every other animal, are susceptible of great 

 modification, and so soon as such modifi- 

 cation becomes advantageous to the species, 

 it will be acquired. 



In leaving the subject for the present, I 

 may be permitted to point out that even the 

 illustration I have taken is not confined to 

 the GeometrcSy as I have confined it. The 

 band in Lepidoptera occurs in other groups 

 besides that I have discussed, but I wished 

 to place the matter on as narrow a founda- 

 as was compatible with a proper under- 

 standing of it, and have therefore written 

 as though it had no wider relation. 



THE "YOUNG NATURALIST 

 ILLUSTRATED CATALOGUE 

 OF BRITISH INSECTS. 



The Genus APHODIUS. 



As promised last month we now give a 

 brief summary of the species of this genus. 

 A more elaborate account of them will be 

 given by an able contributor at some future 

 time, but for the present we give such notes 

 as, with the aid of the two plates, will enable 

 anyone to identify most of the species. 

 Since last month Mr. J. W. Carter has 

 favoured us with A, prodromus, and we 

 shall be glad of specimens to figure ot any 

 other species, given in our list last month. 



Most of the species, both in the larva 

 and imago state, are to be found in dung, 

 particularly that of horses and cows, some- 

 times swarming to such an extent as to 

 make a living mass of matter. 



They are divided into two sections by the 

 size of the scutellum ; in the following 

 species it is large — Frraticus, subterraneus, 

 fossor, hcemorrhoidalis ; in all the rest it is 

 small. The British species are : — 



+ i. Erraticus. This and the next have 

 the body flattened ; elytra brownish yellow, 

 darker in the middle. " Common." N. & 

 S. England, 



2. Subterraneus. Differs in being en- 

 tirely black. " Common." N. & S. England. 



* 3. Fossor. Very convex, a flattened de- 

 pression in front of thorax. " Common." 

 N. & S. England ; Scotland. 



4. Hcemorrhoidalis. Distinguished by 

 large scutellum and red apex to elytra. 

 " Common." N. & S. England ; Scotland, 



* 5. Scybalarius Distinguished by dark 

 shade on side of each elytron, and thorax 

 all black. " Common." N. & S. England ; 

 Scotland. 



* 6. Fcetens. Distinguished from Fime- 

 farms by having the abdomen (see under- 



