326 



Queensland, and to Professor T. Harvey Jolmston I wish to 

 express my gratefulness for permitting me to perform the 

 work there. To him, and to Mr. Henry Tryon, Queensland 

 Goveniment Entomologist, I desire to express my obligation 

 for the loan of indispensable literature, so difficult to procure 

 in Australia. I am also much indebted to the trustees and 

 director of the Australian Museum, Sydney, for the per- 

 mission granted me to examine important publications under 

 their care; and to Mr. W. Rainbow, Museum Librarian, for 

 the facilities which he placed at my disposal. Finally, I 

 wish to express my sincere thanks to Professor T. Brailsford 

 Robertson, of the University of Adelaide, for the many sug- 

 gestions and kindly criticisms he has offered me since I have 

 known him. 



TECHNIQUE. 



The methods employed here have been fairly simple. For 

 the examination of the grosser anatomical processes whole 

 mounts stained or unstained, or partial dissections, so far as 

 these could be made, have been used. For all the finer 

 histological details I have employed sections stained by the 

 Heidenhain iron haematoxylin method, Eosin or acid fuchsin 

 has been frequently used as a counter-stain. Fixation was 

 always made with Bouin's '^picro-formol" mixture. As these 

 methods gave very satisfactory results in the majority of 

 cases nothing more elaborate was attempted. 



PART I. 



On the Structure and Post= Embryonic Development 



of a Chalcid Wasp, Nasonia. 



A. — The External Features. 



The eggs of Nasonia, deposited by the female, beneath 

 the hard shell of the fly pupa, on to the surface of the delicate 

 developing nymph, hatch after a period varjang from thirty 

 to seventy hours, into small white maggots, about '3 mm. in 

 length. These are the larvae in the first instar. 



Tlie larva (fig. 1) is composed of fifteen segments, of 

 which the last two can easily be "telescoped" into the one 

 preceding them. The last segment is difficult to detect in 

 living mat-erial. If, however, the larva is placed in a clearing 

 solution, which causes considerable shrinking in the cuticle, 

 then the segment is unmistakable. 



Of these segments the first two eventually produce the 

 head of the adult wasp ; the next three develop the thorax, 

 while the remaining: ten give rise to the abdomen of the 

 insect. 



Tlie first segment bears the mouth on its ventral side; 

 the lastj the anus; but the larva, though it feeds rapidly, is 



