256 Transactions. — Zoology. 



diverge almost at once, and extend a little within the margins 

 for about half the length of the wing ; at rather more than 

 half their own length a conspicuous cross-vein unites them, 

 and forms thvis a triangular basal cell. The hind- wing has 

 only one vein on the surface, the sub-costal extending for half 

 its length and terminating at the two hooks on the edge. 

 Both wings have faint patches of dark-grey on the surface. 

 The exserted female ovipositor (fig. 14) has a somewhat thick 

 cylindrical base, with a long, slender, curved tube, ending in a 

 slightly-dilated bulb with three or four spines. The penis of 

 the male (fig. 15) is long, cylindrical, with an oval terminal 

 bulb, at the base of which is a ring of spines. The sperma- 

 tozoa (fig. 16) are about -^ Jjjoii^- loi^g > they are wonderfully 

 agile in their motions, and in the specimens observed retained 

 their vitality for more than half an hour after extraction from 

 the male insect. 



This insect has been placed here in the genus Eurytoma of 

 the family ChalcididcB, as it seems to agree better with that 

 than any other, although not entirely satisfying the conditions. 

 The veining of the wings appears to be more like that of some 

 CynipidcB, especially in the triangular basal cell ; but the 

 simple form of the abdomen removes it from that family, and 

 the presence of the distinct segment between the peduncle and 

 the true abdominal region approaches somewhat to the 

 IclmerimonidcB. Eurytoma and its allied genera seem, indeed, 

 to hold an intermediate position between the two families, and 

 on this account the present insect has been assigned to that 

 genus. 



A point of importance remains to be considered. The Chal- 

 cididcB are not usually phytophagous, gall-producing insects, 

 but parasitic on other flies ; and it has always been a matter 

 of doubt whether any of them depart from the rule. A species 

 of Eurytoma is found to do much damage to wheat in America, 

 producing on the stems galls which weaken and destroy the 

 plant ; yet it is not certain whether this fly {Eurytoma hordei) 

 may perhaps not be only parasitic on a larva of Cecidomyia, 

 and that this last larva may not be the real gall-producer. In 

 the present case the galls of Olearia contain, as above stated, 

 dipterous flies (described below), and these are Cecidomyia. 

 Our Eurytoma may thus be merely a " messmate," to use 

 Van Beneden's term, the dipteron being the real plant-enemy. 

 That it is not a true "parasite" seems certain, as, although 

 its larvae and pupa? are found mixed indiscriminately with 

 those of the Cecidomyia, they are in separate cells, and 

 the Diptera in the leaf-blisters are never infested by them. 

 On the whole, I incline to the belief that the Cecidomyia pro- 

 duces the galls on the twigs, and the Eurytoma takes advantage 

 of them as a residence. 



