FLIES. 177 



mer, and is an animal of singular beauty ; 

 its general length is about three inches from 

 head to tail, and the wings, when expanded, 

 measure near four inches from tip to tip : 

 the head is very large, and affixed to the 

 thorax by an extremely slender neck ; the 

 eyes occupy by far the greatest part of the 

 head, and are of a pearly blue grey cast, with 

 a varying lustre : the front is greenish yel- 

 low, the thorax of the same colour, but 

 marked by longitudinal black streaks ; the 

 body which is very long, slender, and sub- 

 cylindrical ; is black, with rich variegations of 

 bright blue, and deep grass-green; the 

 wings are perfectly transparent, strengthened 

 by very numerous black reticular fibres, and 

 exhibit a strong iridescent appearance, accord- 

 ing to the various inflexions of li^ht ; each 

 is marked near the tip by a small oblong 

 square black spot on the outer edge ; the legs 

 are black, and the tail is terminated by a 

 pair of black forcipated processes, with an 

 intermediate shorter one of similar colour. 

 Sometimes this insect varies ; the spots or 

 marks on the abdomen and thorax being red, 

 or red-brown instead of gi-een. The life of 



