EURYT0MID.E. 11 



of Europe have a pale spot on each side of the fore border of the 

 prothorax, and in two of them the prothorax is wholly yellow. Their 

 power in leaping is very slight as compared with that of most of the 

 Chalcidise. 



Dr. Walsh, in his Essay on the Eurytomida?, says, " In several 

 cases Eurytomidous forms, that appear to belong to the same species, 

 present more or less constant differences when they infest different 

 species of insects. Such forms seem to deserve a distinctive name, 

 which 1 have accordingly given to them —classifying them as mere 

 varieties." He adds, "If such a so-called variety confines itself 

 exclusively to that particular insect which it is actually found to 

 infest, then I should infer that it cannot interbreed habitually with 

 the other forms referred to the same so-called species ; because, if it 

 did so, it would inevitably, by the Laws of Inheritance, acquire a 

 propensity to attack all the different insects which are attacked by 

 the other forms provisionally referred to the same species. Conse- 

 quently, upon this latter supposition, I should pronounce such a 

 so-called variety to be in reality a distinct species." There are 

 instances of a species of Chalcididse being parasitic on several very 

 different insects, without showing any variation. Some other 

 observations of Dr. Walsh indicate that he considers difference of 

 size in varieties or species to be owing to the difference in size of the 

 insects which they infest; for instance, E. plumata, the largest 

 European species of Eurytoma, that inhabits the large galls formed 

 by Urophora Cardui on thistle-stalks, thereby excels in size the very 

 small Eurytoma (E. curta?) that emerges from the little galls on 

 Rosa spinosissima. 



Since the notes on Isosoma were published in the ' Zoologist ' I 

 found a passage in Nees ab Esenbeck's Hym. Ich. aff. Monogr. vol. 2, 

 which shows that Dr. Nees discovered one of the Eurytomidae to be 

 herbivorous in 1834. In his description of Eurytoma Rosae, p. 415, 

 he observes that he formerly confounded it with E. (Isosoma) verti- 

 cillata, and that he had ascertained it to be the maker of the galls of 

 Rosa centifolia. In p. 431 he describes Eulophus Eurytomae, a 

 parasite of the above species, which from his description is certainly 

 a Eurytoma, not an Isosoma, and is a proof that the Eurytoma? are 

 not all parasitic. Whether one species of this family is sometimes 

 parasitic on other insects and sometimes herbivorous, and has thus 

 the choice of two ways of perpetuating its existence, has yet to be 

 ascertained. E. Rosae is not the Eurytoma of Rosa spinosissima 

 before mentioned. This Eurytoma and one of the Cynips tribe dwell 

 in the same galls, but the gall-fly may be one of the " Iuquilinae," and 

 not a victim of the Eurytoma. 



Fossils have been termed medals of creation, and, according to Dr. 

 Walsh and others, insects, by means of their differences and affinities, 

 are living medals which illustrate a long succession of earlier epochs. 



