519 



Fig. 36. Longitudinal section of antenna (x4o0). Defaeca- 

 ting larva. Note invagination of "padding" tissues, for example 

 at X. 



Fig. 37. Portion of wing of fonr-day pupa, showing hairs, 

 and the characteristic folding. Degenerate nuclei also seen 

 (x750). 



Fig. 38. Hooks of hind wing of imago, showing scattered 

 wing nuclei: hook ''roots" — remnants of embryonic cells — are 

 clearly seen. 



Plate XIX. 



Fig. 39. Stigmal view of fore wing, imago (xl200), showing 

 the four problematic sense organs (speed indicators ?). 



Fig. 40. One of the sense organs of stigmal vein (x2000). 



Fig. 41. Section through a joint membrane^ — modified cuticle 

 (x500). 



Fig. 42. Section through free part of ovipositor of four-day 

 pupa (x600). 



Fig. 43. Vertical section through a cephalic phragma (thirty- 

 six hour pupa) ; developing antennal muscles are seen ; also a fat- 

 body and degenerating leucocytes (xl200). 



Fig. 44. Fore wing of twenty-four hour pupa. Note shrink- 

 ing within the old cuticle. Note also the two clear channels each 

 containing tracheoles (x80). 



Fig. 45. Vertical section through the wing of four-hour 

 pupa, to show the band of mesodermal cells (k) growing down- 

 wards, to enter the anterior clear channel (x500). 



Fig. 46. Optical section of tip of tarsus of imago (x750). 



Fig. 47, Section through head of larva in first instar, right 

 half only shown (x500). 



Fig. 48. Section through mandibles of larva twelve hours 

 after defaecation. 



Fig. 49. Section along part of first segment of antenna, to 

 show nerve endings or tactile bristles ( x 1200) — four and a half day 

 pupa. 



Fig. 50. A tactile bi'istle from ovipositor appendage, showing 

 the receptor ceU (xl500). 



Fig. 51. Sense cells below cuticle of antennal joint of imago 

 (xl500). ' . 



Fig. 52. Longitudinal section through the "olfactory seg- 

 ment" of antenna, showing the suspended sense organs (xl200). 



Fig. 53. Surface view of one of the more anterior antennal 

 segments, showing four auditory organs (xl200). 



Fig. 54. Cells of the optic imaginal disc of larva in first 

 instar (x2000). 



Plate XX. 



Fig. 55. Vertical section through imaginal disc of eye in 

 larva of first instar (xlOOO). 



Fig. 56. Ommatidia from developing eve at time of defae- 

 cation (x 1500). 



Fig. 57. The same, eight hours later (xlSOO). 



Fig. 58, a, b, c. The same, eight hours later than fig, 57 

 (xl500). d. The same, in tran verse section. Note the seven 

 sheath cells (xl500). 



Fig. 59. Ommatidium from pupa, four hours old (xl50O). 



Fig. 60. Ommatidium of four-hour pupa in transverse sec- 

 tion. Note onlv six sheath cells. 



