TRIFIDsE. 123 



gists' Annual for 1871 that it agreed to the minutest detail 

 with the type of P. acuta in the British Museum. The types 

 of P. verticillata , Gn., and of P. acuta, Walk., in the British 

 Museum, are now placed as forms of P. criosoma, Dbld., a 

 species closely allied to P. iota and P. pulchrina, especially 

 to the latter, but having the upper portion of the Y-mark 

 filled up into an irregular spot, and the lower portion sepa- 

 rated to a greater distance and forming another spot of nearly 

 the same size. There is before this marking an obscure- 

 double curved line or stripe placed obliquely almost across 

 the base of the wing. Still, it might readily be pasfed 

 over as a variety of P. pulchrina. 



Dr. P. B. Mason has recently identified this with the 

 species named P. bimacidata by Stephens, of which but one 

 reputed British example was known. In the National Col- 

 lection this species— from North America— is placed next to 

 P. eriosoma. In these various forms the insect is found, not 

 only in North America, but over large portions of Asia, 

 Africa, Australia, and New Zealand ; but the two or three 

 specimens reputed to have been found in this country can be 

 .nothing more than accidental introductions.) 



9. P. gamma, L.— Expanse l\ to If inch. Fore wings 

 rather pointed, silvery-grey, or purplish grey-brown, hinder 

 portion extremely glossy ; a complete and very distinct Y-spot 

 in brilliant silver in the middle is surrounded by black cloud- 

 ing. Hind wings smoky yellowish-white with a broad smoky- 

 black hind border. 



Antennas of the male simple, long, minutely and closely 

 ciliated, grey-brown ; palpi rather short, moderately tufted, 

 dark slate-brown ; eyes large, leaden-brown, lashes erect ; 

 head prominently tufted, the tufts divided by a deep cross- 

 channel beneath the antennae; thorax dull brown, crossed 

 . with fine lines of deeper brown and white which doubly bar 

 the collar, triply the shoulder lappets, and edge every tuft of 

 the large compound back crest ; fascicles smoky-white ; abdo- 



