158 THE ENTOMOLOGrlST. 



caterpillars, while the much smaller larvae of the males sometimes 

 contain hut a single parasite. These pupse are dark chestnut- 

 brown in colour, with distinct articulations ; their length is 

 nearly three lines, and they are of the ordinary coarctate form. 

 The perfect insect is a brilliant green fly, the abdomen being 

 almost blue ; the scutellum is bordered with fulvous, and the 

 legs are black ; the whole insect is also covered with numerous 

 black bristles ; its length is about three lines. A description of 

 this fly may be found in the ' Catalogue of New Zealand Diptera,* 

 where it is described for the first time under the name of 

 Eurig aster marginatus . 



Among a large number of the exuviae of this species I found 

 one which had not emerged. Knowing that all the individuals 

 of a single brood of dipterous insects always appear within a 

 few hours of one another, I was anxious to ascertain what had 

 occasioned the protracted emergence of this specimen, and in 

 order to do so I enclosed it in a small tightly-fitting box. On 

 examination about ten days afterwards I discovered eighteen 

 small Chalcids had escaped through a small round hole near its 

 anterior end ; four of these are considerably smaller than the 

 rest, but do not differ in any other respects, and are no doubt 

 males. 



Owing to my very imperfect knowledge of the New Zealand 

 Hymenoptera, I think it would be useless for me to attempt to 

 describe an obscure species of this kind at present. I therefore 

 enclose specimens, should they at any time be required, and 

 leave the description to someone who is better able to perform 

 the task than myself.* 



I have not yet been able to ascertain how the Chalcid 

 introduces its eggs into the Dipteron ; nor is it likely to be 

 discovered, except by the most minute observation. It is certain 

 that a full-grown maggot would not sufiice to nourish eighteen 

 Chalcid larvae, which collectively equal it in bulk after it had 

 ceased feeding ; hence it is evident that the eggs are not 

 deposited in the dipterous larva when it has left the caterpillar. 

 If, on the contrary, they are introduced into the maggot while it 

 is within the Liothula larva, the hyperparasite must either pro- 

 miscuously deposit in every caterpillar it comes across all the 



* Two specimens of this Pteromalus, and a third partially destroyed, are deposited 

 in the British Museum.— E. A. F. 



