THE YOUNG NATURALIST. 



405 



with black tips, head and legs black, claspers j 

 dull red. It is a larva rarely mat with, and j 

 Mr. G. F. Mathew informed Mr. Buckler, 

 that "they are seldom seen on their food 

 plant, but generally on a deal leaf in its 

 immediate neighbourhood, or a twig above j 

 if 



Pupa. — Much curve! in outline, and 

 warty. Grey brown in color, with a few 

 paler dots. 



Pood Plant —Dog Violet ( Viola canina). j 

 Times of Appearance.— The imago 

 emerges in May, and continues on the wing 

 during the greater part of June. The larva! 

 is hatched at the end of June or beginning of j 

 July, but does not as a rule feed up till 

 spring in this country. Sometimes, however, J 

 it does so, when the imago may be found in ; 

 September, and the second brood of the I 

 larva appears the same month, to hybernate I 

 till April. 



Habitat. — A common wood insect, re- 

 curring throughout the country, and generally 

 in some abundance. It is found all over 

 Europe, except a few isolated localities, such 

 as the Spanish Peninsula, Corsica, &c. 



Variation. — This insect varies similarly 

 to some others of the genu^. The black 

 spots become larger until they coalesce, 

 sometimes forming bands, &c. A specimen 

 in Mr. Briggs' cabinet has the base of the 

 hind wing entirely black. Others vary in the 

 ground color, which becomes buff, orange, 

 or almost white. Fig. 3 a is a remarkable 

 specimen in Mr. C. A. Briggs' collection, 

 taken at Folkstone, 1876. A very curious 

 one is in the collection of Mr. H. Vaughan. 

 It is of the ordinary form in all respect s, 

 except that the spots on the upper side are sil. 

 very or rather leaden in color, instead of being 

 black as usual. Two varieties are named, 

 Thalia, Hubn., occurring in Sweden and Nor- 

 way, andFz';^a/,Herbst, also found in the more 

 northerly parts of Europe. The latter like so 

 many other boreal specimens, is smaller and 

 darker the spots forming band s as named above. 

 We do not know anything further of Thalia, 



1 



possibly one is but another name for the 

 other. 



Parasites. — None known to us. 



CO N C H OL 03/. 



LAND AND FRESH-WATER SHELLS. 

 By H. T. Robsox, Stockton-on-Tees. 



FAMILY, MYTILACEA. 



Genus, Drsissena. 



The shell is somewhat triangular, with a 

 plate across the narrow pointed part of each 

 valve below the umbo, to which an auxiliary 

 muscle is attached, the hinge is without teeth. 

 The mantle of the animal is closed with the 

 exception of an opening for the passage of the 

 foot in front, and two fur the siphons behind. 

 There is only one species Polv iiorpln. 



Polymorpha.— The shell is triangnlar as 

 already described, and with wavy zigzag mark- 

 ings of dark- brown on a lighter ground color, 

 the interior is bluish white. It is a natural- 

 ized mollusc, but is very prolific rind is now 

 common throughout the country, in rivers, 

 docks, canals, &c. 



. FAMILY, NAIADES. 

 Genus, Anoclonta. 



The shell is oval with equal valves, 

 the anterior side short ; the genus may be 

 distinguished by the hinge being without teeth. 

 There is but one species, Cygnea. 



Cygnea. — The shell is thin, ova! but rather 

 variable in shape, and covered with an epider- 

 mis, green or olive brown ; the growth of the 

 valves is indicated by concentric ridges, the 

 hinge is on the posterior side and without 

 interlocking teeth. It may be found in rivers, 

 streams, canals, &c, throughout the country. 

 Genus, Unio. 



The shells of this genus are rather similar to 

 the last in form, but with the valves thicker, 

 and the hinge with interlocking teeth, the 

 anterior side is very short. The species are 

 T'umidus, Pictorum and Margaritifcr. 



Tumidus --This is somewhat oval, the 



