FORMICA. 



263 



pour les poils et rufa pour la couleur. II y a aussi des fourmilieres inter- 

 mediaires en tout point. Les differences dans la longueur respective des faces 

 du metanotum (F. polyctena Forst) n'ont aucune Constance ; elles varient 

 enormement dans la meme fourmiliere." 2 



$ " F. rufo-pratensis. Abdomen ni mat ni luisant partout, plutot luisant. ' ' 3 



Forel's var. rufo-pratensis embraces all the intermediate forms 

 between F. rufa L. and F. pratensis Retz. ; it is probable that the 

 polyctena Forster and the piniphila Schenck, which are usually 

 regarded as synonyms of rufa, both represent some one of these 

 intermediate forms, but it is quite useless to try and fix a name to 

 any particular form. Emery states : " Old authors have dis- 

 tinguished several forms on account of the different condition of 

 the erect hairs in the worker : the forms with hardly any bristles on 

 the head and thorax embrace the F. rufa Foerst. and polyctena 

 Foerst. ; distinctly bristled make F. piniphila Schenck. The latter 

 represents the first degree of a variety of intermediate forms going 

 over to F. rufa pratensis which represent var. rufo-pratensis For. 

 ^, ?, and < declare themselves in all their characteristic distinctions 

 (colour, hairiness, shining of the gaster in the $, etc., which distinc- 

 tions appear to combine together in every possible way and stage) 

 as bringing together rufa rufa and rufa pratensis." 5 



It is usual with transitional forms that all the individuals in one 

 colony belong to the same form, and Forel gives a valuable table to 

 illustrate the different zoological and embryological forms that may 

 occur 1 : 



