I 



DEVELOPMENT OF CHALCIDS 327 



studied by Seurat (10). The general form and the number and 

 order of opening of the spiracles are the same in both cases. 

 Certain parasites of Coccidae, described l)y Imms (8) show 

 a reduction in the number of spiracles from behind forwards ; 

 but in one , A p h y c u s m e 1 a n o s t o m a t u s , rudimentary 

 trunks of the tenth pair appear during development, though 

 they never become functional. Ectoparasitic Chalcidae, such 

 as Asaphes and Torymus, have probably retained 

 certain primitive features, such as the full number of spiracles, 

 which have been lost in the more specialized and frequently 

 hypermetamorphic forms, found among the endoparasitic 

 members of the super-family. 



Pupation and Emergence. 



When the remains of the Aphidius have been completely 

 devoured, the gut of the hyperparasite opens, the meconium 

 is voided, and the Chalcid pupates within the cocoon pre- 

 viously woven by the Aphidius inside the skin of the aphid. 

 The pupal stage lasts from fourteen to sixteen days, for 

 Asaphes and Pachycrepis; but in a single observed 

 instance of Pachyneuron the period of pupation was only 

 ten days. When ready to emerge, the imago gnaws a hole in 

 the cocoon and creeps out. The adults lived in confinement 

 for from four to seven days, and fed on the sap oozing from 

 cut leaves, and on honey-dew which had fallen from the aphides. 



At least two generations may occur in the year, but the exact 

 number was not ascertained : it is probably dependent on the 

 number of hosts obtainable. There is no evidence to show 

 how these Chalcids pass the winter. 



Eemarks on the Bionomics of Hymenopterous 

 Parasites in General. 



The relations of any animal to its enemies, predatory or 

 parasitic, form what may be termed a bionomical complex ; 

 although the limits of such a complex are often difficult to 

 determine, especially when the enemy has a wide choice of 

 alternative food or host species. 



NO. 20)2 A a 



