8 



the back and a legless grub emerges. The larva at this, second, 

 stage, is like a small sack filled with a creamy substance that re- 

 minds one of the pronymph of xVluscids; it is thicker at the an- 

 terior end, has no trace of legs or ventral protuberances and no 

 visible trophi. The alimentary tract can be distinguished as a 

 fine tube, but I have been unable to trace it to an anterior or 

 posterior opening; it is apparently functionless and nourishment 

 is obtained through the hypodermis. Two dark pigmented spots 

 are visible below the surface from which the imaginal eyes 

 eventually arise. 



The size to which the larva grows depends upon the amount of 

 space and food it receives. One female, the only parasite in a 

 female P. vitiensis, filled the entire abdominal and thoracic cavity. 

 Generally there are several parasites in the same host, one con- 

 taining as many as fourteen of various sizes. As the male larva 

 increases in size, the integument becomes slightlv chitinized and 

 the mouth parts became visible. In the next larval stage that^ I 

 have been able to trace, which I will term the third, the anterior 

 end is greatly constricted and the form similar to the 

 puparium. The imaginal eyes are greatly advanced and the 

 imaginal discs of the thoracic appendages distinguishable. Two 

 larvae at this stage had the mouth parts so very distinct that I 

 doubted if they could be E. tenuicornis, but as during my six 

 montlis' stay in Fiji I found only two parasites upon the adult or 

 larval P. vitiensis, I am forced to believe that they are a larval 

 form of this Stylopid. These are figured in Figs, i, 2 and 3 and 

 explain the mouth parts visible on the head-cap of the male 

 puparium (Fig. 4). 



The puparium (Fig. 5) is homologous to that of Muscids, being 

 the skin of the instar preceding the pupal stage, whether that in- 

 star l)e called larval, pseudo-pupal or coarctate-larval. A skin is 

 often found attached to the posterior end of the puparium show- 

 ing that an ecdysis takes place at that stage. 



All the cephalic and thoracic appendages of the adult can be 

 distinguished in the pupa before the anterior end of the puparium 

 is pushed through the pleura of the host. 



Across the dorsal surface of the cephalic cap of the male 

 puparium. below the labium, runs a depression, the segmental 

 division between the head and prothorax (Fig. 4). In the fe- 

 male a folding back of the labium and adjoining parts forms an 

 opening at this spot leading to the brood-chamber (Fig. 6). 



At an early stage before the apical cap of the puparium is 

 exerted, this segmental depression is distinct all round and the 

 prothoracic spiracles are plainly visible ; thus we see that the 

 earlier writers were correct in calling the exserted part of the 



