habits of certain species of Eurytomiclcs. 321 



O'OS to 0'12 in. long, black, and of the usual hymen- 

 opterous form. 



xinother species of Isosoma was also described by- 

 Prof. French in the same memoir, under the name of 

 Isosoma elymi, the larvae of which were found on the 

 interior of the culms of Elyimis canadensis in about the 

 middle internodes of the stalks, very much as the larvae 

 of the preceding species are to be found on the interior 

 of wheat culms. While, however, the wheat larvs are 

 generally just above the joint, these maybe found in any 

 part of the interior of the internode. Both feed upon 

 the soft tissue of the interior of the stalk, and do not 

 produce any enlargement ; the only noticeable effect from 

 the outside is that internodes containing larvae are 

 usually shorter than the others. The larvae are footless, 

 about 0*10 in. long when still, and 0*04 in. wide in the 

 widest part, with brown jaws. Colour very pale yellow, 

 and, like the preceding, there appear to be slight pro- 

 jections from the sides of the body at times. 



Specimens of the first of these two species having been 

 submitted by Prof. French to Mr. Riley, and to myself 

 through Miss Ormerod, prove to belong not to Isosoma, but 

 are "a species of Eupelmus, parasitic, doubtless, on some 

 of the wheat- stalk feeders, and probably on some species 

 of Clilorops'' ('Amer. Naturahst,' March, 1882, p. 247). 



An additional species of Isosoma which affects wheat 

 has just been described by Mr. Eiley in the ' Rural New 

 Yorker,' and again at greater detail in the 'American 

 Naturalist' for March, 1882, under the name of Isosoma 

 tritici, received from Tennessee and Missouri. Although 

 congeneric with the joint worm (I. hordei), it differs 

 widely from the latter in habits and appearance. The 

 joint worm forms a gall -like swelling at a joint near the 

 base of the stalk, whilst the species under consideration 

 feeds on the interior of the stalk between the joints 

 higher up, without causing a swelling. The larva 

 figured by Mr. Riley is long and quite cruciform, with 

 the segments of the body distinct and of nearly equal 

 width throughout its whole length ; the head is furnished 

 with two very small filiform porrected antennae, arising 

 from a thickened basal joint ; the mandibles are 

 deflexed, nearly triangular, acute at the tip, with a 

 small conical tooth near the apex of the inner margin. 

 Mr. Riley adds that "it is worthy of remark that this 

 new species seems to be quite closely related to the 



TRANS. ENT. SOC. 1882. — PART II. (jULY.) 2 T 



