Fig. 
Fig. 
Fig. 
Fig. 
Fig. 
Fig. 
Fig. 
Fig. 
Fig. 
Fig. 
Fig, 
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16, 
Lf. 
Annals Entomological Society of America [Vol. VIII, 
Section through a wing rudiment after the two layers have come together 
and a narrow, lighter zone has appeared between them. X 875. 
. Transverse section of entire wing rudiment from which preceding figure 
was drawn. X 105. 
Median part only of a section through a wing rudiment. This shows the 
early formation of the middle membrane and of the perpendicular 
strands. > 1100. 
Section through a young external wing, lateral stage than preceding 
figure. > 1100. 
PLATE X XI. 
Section of a wing at a later stage showing the wandering of many of the 
nuclei to the middle membrane in which a number of these nuclei, 
much reduced in size and clearness, can be seen; other nuclei are visible 
on the perpendicular strands. To the right a small outer portion of 
the hypodermis and the cuticula have not been drawn. X 1100. 
A small part of the same section more highly magnified to show the 
wandering of the nuclei from the hypodermis to the middle membrane. 
Only the inner edge of one layer of hypodermis is drawn and, in it, the 
ends of five nuclei. Opposite this is shown a part of the middle mem- 
brane and between these two the perpendicular strands on which are 
seen some of the wandering nuclei. The position of this view is shown 
by the space between the two lines at a, in the preceding figure. > 1700. 
Section of a wing at a later stage, shortly before the casting of the last 
larval skin. All the nuclei in the middle membrane are reduced in 
size and the perpendicular strands greatly elongated. X 740. 
Section of a wing at a still later stage of development. The middle 
membrane in which are seen a few of the nuclei that have wandered 
into it from the hypodermis is narrow and much more membrane like 
than in the preceding figures. X 740. 
PLATE XXII. 
Section of a wing from a pupa after the last larval skin has been cast, 
the body contracted and the wings straightened. The nuclei of the 
hypodermis are nearly all arranged in a single row along the surface 
and many of the perpendicular strands extend entirely across the 
wing. The middle membrane is no longer continuous. X 740. 
A little later stage showing that at this part of the section the middle 
membrane has entirely disappeared. Cuticula not drawn. X 740. 
Section from the wing of a pupa before its final folding has commenced. 
The middle membrane has again formed as a continuous layer. > 740. 
Section of a pupal wing after the last folding has started. Cuticula 
not drawn. 740. 
Section of another wing of about the same age. Cuticula not drawn. 
x 740. 
Section through the wing of an old pupa. The wing of this specimen 
is much folded and shows the entire and final disappearance of the 
middle membrane. The perpendicular strands again pass across the 
wing. Cuticula not drawn. X 740. 
Section of the wing of an imago shortly after its emergence. The old 
hypodermis is now represented by a thin layer of protoplasm con- 
taining a few shrunken nuclei. X 740. 
Section through the wing of an adult.. X 740. 
