NATURAL HISTORY. 



furnished with two hooks. The pupa is formed within the mature larva skin, of which, however, 

 it occupies only the wider anterior part, and in this natural " cigar-boat " it floats freely in the water 

 until it arrives at maturity, when the perfect fly escapes through a slit in its protective covering. 

 The flies are found in summer upon flowers near water, and upon the leaves of aquatic plants. The 

 species of Stratiomys are numerous in Europe, and some occur in various parts of the world, but 



METAMOBPHOSES OF STRATIOMYS CHAMELEON. 



chiefly in the northern hemisphere. Species of several allied genera also pass their preparatory 

 states in the water. 



Of the rest, some, such as Pachygaster ater and Clitellaria ephippium, live as larvae in rotten 

 wood, and the latter is said to deposit its eggs in the nests of Formica fidiginosa. The larvae of the 

 genus Chrysomyia, which includes bright metallic- coloured flies of small or moderate size with an 

 unarmed scutellum, feed upon decaying vegetable matter, and the flies frequent hot-beds ; and 

 those of the larger but equally brilliant species of Saryus have the same habits, and are to be 

 found in manure and garden mould. The larva of Sargus cuprarius is said to attack turnips. 



The second group of the family, which may be named XYLOPHAGIDES, is characterised by 

 its species having seven or eight free abdominal segments. It includes a few genera, the larvae 

 of which, so far as is known, live in decaying wood. In Britain this group is chiefly represented 

 by the genus eris, including metallic flies of moderate size, with from four to eight spines on the 



