204 Annals Entomological Society of America [Vol. VIII, 
more or less degenerated during the prepupal period and in 
places the bases of the cells either end free or become fused and 
anastomosed with each other.”’ 
It might also be well to give a very brief account of the 
early development of the wings of Platyphylax taken from an 
earlier paper, Marshall (4), 
In the earliest, newly hatched, larve sections through the 
thorax fail to show any modifications of the hypodermis at 
those areas where the wing rudiments will later appear. Very 
soon, probably in the second instar, four small, disk-like thick- 
enings can be seen; they are formed by the elongation of a few 
cells of the hypodermis (Text-figure I, A) and are found on each 
side of the wing-bearing segments, dorsal to the legs. These 
disks, which remain continuous with the hypodermis, soon 
invaginate and each, sinking below the surface, forms a small 
pocket, the peripodial cavity, at the bottom of which the disk 
is situated (Text-figure I, B). The hypodermis consists of a 
single layer of cells with a basement membrane along its inner 
surface, this membrane is the same on the disk and on the sur- 
rounding hypodermis both of the peripodial cavity and that 
covering the thorax. The disks never recede far from the sur- 
face from which they invaginated and soon commence to evag- 
inate (Text-figure I, C). The peripodial ‘cavity remains in 
communication with the exterior through the peripodial pore, 
the opening formed by the original invagination. At first the 
invaginated disk was, from a surface view, circular, it gradually 
elongates and when evagination takes place the wing rudiment 
is like a flattened sack; each wall of this sack consists of a single 
layer of hypodermal cells and a basement membrane which 
forms the inner, adjacent, part of each wall. In this way the 
basement membrane of each wall comes to oppose and lie 
adjacent to that of the other wall, and, as the walls come closer 
and closer together, the two basement membranes lie against 
each other, touch, and apparently fuse. This is not true over 
the entire inner surface as here and there this fusion of the two 
layers has not occurred and certain elongated free spaces remain, 
these are the developing wing veins. 
The wing rudiment increases in size and a slight bending is 
necessary in order that it may remain within the peripodial 
cavity; the expulsion from this cavity takes place shortly after 
the larva has closed its case preparatory to pupation and the 
