DESCRIPTIVE NOTICES OF CONSPICUOUS SPECIES 119 



there are short oblique blackish streaks ; the spiracles 

 are whitish ; it feeds on clover and bird's-foot trefoil in 

 April, June, and August. 



The perfect insect may sometimes be noticed asleep 

 in the evening on the blossoms of rushes. 



Allied to the preceding, but with the fore-wings of 

 the male of a purplish-blue, is the Silver-studded Blue 

 (Polyommatus ^Egon). It frequents sandy heaths and 

 chalky downs, and is generally very plentiful where it 

 occurs. It may be always distinguished with certainty 

 from the Common Blue by the two following cha- 

 racters : on the underside of the fore-wings there are 

 no spots between the central spot and the base of the 

 wing, in the Common Blue there are two black spots in 

 white rings here ; secondly, on the underside of the 

 hind-wings there are three or four bluish metallic spots 

 near the hind margin, these are not at all represented 

 in the Common Blue. 



FAMILY IV. 



POLYOMMATUS AGESTIS. THE BKOWN 

 AKGUS. 



This frequents chalky and limestone localities; in 

 the south it has the regular form of Agestis, but in the 

 north it puts on the form of Artaxerxes. 



The expansion of the wings is about 1 inch. The 

 wings are of rich brown, with a marginal band of 

 central spots in the southern form, Agestis ; the fore- 

 wings have a central black spot ; in the northern form, 

 Artaxerxes, this is replaced by a white spot. 



On the underside in Agestis the white spots have 

 black centres ; in Artaxerxes the black centres are 

 suppressed, the spots being entirely white. 



