1909.] 127 



ON THE BRITISH SPECIES OF CHALCOIDES, , Yovoras. 

 MY JAMES EDWAEDS, F.E.S. 



The insects of this genus are well distinguished from their 

 immediate allies by the strongly metallic colour of their upper-side, 

 and the fact that their food-plants are exclusively Salicinece. They 

 are highly interesting to the student of variation and the despair of 

 makers of analytical tables, though they are easy enough to distin- 

 guish accurately when once their real differential characters have 

 been grasped. All our s|jecies are admirably dealt with by M. Bedel 

 in vol. V of his Faune Col. Bass. Seine, and I think it best to adopt 

 the names which he there employs. It would appear from the 

 literature that blue forms of most of our species are not uncommon 

 on the Continent, but, according to my present information, they are 

 decidedly rare with us and apparently confined to south-eastern 

 England.* Sharp's Catalogue of 1871 gives four species, nitidtiJa, 

 helxines, auratn and chloris ; in the second edition (1883) smaragdina, 

 Foudr., is added, but of this no English description appears to have 

 been available until the publication in 1890 of the fourth volume 

 of Fowler's Col. Brit. Isl., where it is said to have the interstices 

 of the thorax, as well as those of the elytra, finely rugose. 1 have 

 never met with an example exhibiting that character and am not 

 acquainted with any Continental work in which it is mentioned. 



The majority of one's specimens may be segregated by the 

 characters given in the following table, but the more prominent 

 varieties, named and otherwise, merit special mention. 



1. Elytra with the interstitial punctures extremely fine, the rows of punctures 



regular throughout 2. 



— Elytra with the interstitial punctures almost as large as those in the rows, the 



latter irregular in the scutellar region nitidula, L. 



2. Antennae not parti-coloured 3. 



— Antenna) distinctly parti-coloured, the first four joints yellow, the rest black... 



plutus, Latr. 

 {chloris, Foudr.). 



3. Antennse red-yellow, becoming gradually a little darker from about the middle 



to the apex, or entirely red-yellow. Thorax and elyti'a concolorous 4. 



— Antennae blackish, that colour usually passing gradually into red-yellow at a 



greater or lesser distance from the base. Thorax and elytra varicolorous... 



atirata, Marsh. 



4. Thorax at the base evidently narrower than the base of the elytra, its punctura- 



tion very coarse and nearly or quite as deep as that in the elytral striae ... 



fulvicornis, Fab, 

 (smaragdina, Foudr.). 



* The blue form (cj/awea, Marsh) of C. awea, Geoff., i.s found commonly in all its variations 

 on poplar and aspen in the Oxford district.— J. J. W. 



