LIST OF ILLUSTRATIONS.

PLATES.

Page

Plate 1. Eggs of certain Drosophilinse..........................................     18

2.  Scaptomyza adusta, male; Drosophila busckii, male; Drosophila funebris,

female............................................................     64

3.  Drosophila immigrans, male; Drosophila melanogaster, male; Drosophila me-

lanica, female.....................................................     84

TEXT-FIGURES.

Page

Fig. 1. Anterior spiracle of third-stage larva of Drosophila funebris...............    20

.2. Cephalopharyngeal skeleton of third-stage larva of Drosophila melanogaster.    21

;3. Cephalopharyngeal skeleton of third-stage larva of Drosophila funebris.....     21

A. Cephalopharyngeal skeleton of third-stage larva of Scaptomyza adusta.......     21

.i5. Wing of a newly emerged Drosophila simulans that has not yet unfolded.....    23

(6. Head of Drosophila robusta...........................................     25

' 7. Side view of thorax of Drosophila funebris (diagrammatic)................     27

,8. Wing of Drosophila melanogaster.......................................     29

■^^9, 10, 11, 12. Ovipositor plates...........................................     32

"13, 14, 15, 16. External male genitalia......................................     34

17. Oblique section through spermatheca of Drosophila obscura, showing sperm

inside............................................................    35

18-31. Spermathecse, magnified 250 diameters...............................    36

32-43. Spermathecse, magnified 250 diameters...............................    37

44.  Diagram of chromosome groups found in the Drosophilinse (after Metz).....    39

45.  Head of male, Drosophila melanogaster.................................     92

46.  Head of male, Drosophila simulans.....................................    92

47.  Drosophila obscura.    Front leg of male, showing two tarsal combs..........     93

48.  Drosophila virilis.    Head..............................................    97

.49. Drosophila superba.   Wing of type specimen............................   105