112 
Psyche 
[December 
THE HISTOLOGY OF THE WING PADS OF THE 
EARLY INSTARS OF PTERONARCYS PROTEUS 
NEWPORT (PLECOPTERA) 
By R. P. Holdsworth, Jr. 
Biological Laboratories, Harvard University 
Several very thorough papers have been published on the 
wing development of holometabolous insects. The differen- 
tiation of the wing, however, is so rapid that investigators 
are by no means unanimous as to the mode of formation of 
the blood lacunse about which the adult wing veins 
subsequently form. Marshall (1918), studying Platyphlax 
designatus Walker, a trichopteran, stated that lacunse de- 
velop in the wing Anlage of the last nymphal stage and that 
tracheae do not enter until the wing has everted. Hunder- 
mark (1985) investigated Tenebrio molitor and reported 
that tracheae grew into the newly everted wing disc and that 
later lacunae formed about them. Kuntze (1935) in his ex- 
haustive studies of Philosamia cynthia Drury (Lep.) 
claimed that lacuna formation preceded the entrance of the 
tracheae and that lacunae developed inward from the margin. 
Waddington (1939) speaks of the formation of vein lacunae 
in Drosophila wings as being the fusion of small local lacunae 
along the site of the presumptive adult vein. He does not 
refer to the method of formation of the small lacunae nor are 
wing tracheae mentioned in his paper. 
From these studies and other investigations on holometa- 
bolous insects, it is not possible to determine the ancestral 
mode of lacuna formation. To elucidate the problems of la- 
cuna formation and differentiation of wing epithelium one 
would logically turn first to the Heterometabola, but no his- 
tological investigation of any scope has been undertaken. 
Tower (1902) sectioned a first stage nymph of Anasa tristis 
De Geer (Hem.) and saw disc-like hypodermal thickenings 
in the dorso-pleural region on the wing bearing segments. 
At the time of the first moult the discs evert to form wing 
