96 Bulletin of the Brooklyn Entomological Society Vol. XIV 
doubtless the important feature leading to the development of 
complete metamorphosis. The quiescent pupal stage is not so 
much the result of the influence of cold, as the result of pro- 
found internal changes through which the very different adult 
form is assumed. There is a profound change in the chemical 
nature of the blood (the blood of a larva about to pupate, if in- 
jected into a young caterpillar will paralyze the latter), a break- 
ing down of certain larval tissues, etc., and the building up of 
adult structures, during the pupal stages, so that there is small 
wonder that most pupz are unable to lead an active existence 
while these conditions last; and I cannot believe that the pres- 
ence or absence of cold would have any effect upon the origin of 
such a phenomenon. 
Adaptation to aquatic life during the immature stages of de- 
velopment, is another feature which has enabled some very primi- 
tive insects to establish themselves in temperate climates (and in 
the case of such insects as Grylloblatta, protected existence under 
stones has served the same purpose) ; but there is no real evi- 
dence for considering that the first winged insects were aquatic 
in their immature stages. The different location of the gills and 
the different means of adapting themselves to aquatic life even 
in the lower forms would clearly indicate that this feature is a 
comparatively recently acquired adaptation, produced more or 
less independently in different groups of insects; and the de- 
velopment of the tracheal system in the embryonic stages, very 
evidently points to the fact that aérial respiration was the most 
primitive one in insects as a whole, while aquatic respiration has 
been more recently acquired. The structures which Handlirsch 
considers as organs serving the purpose of gills in Palzodicty- 
optera (which were among the first winged insects to be evolved) 
are clearly nothing but paranota, which occur in a great number 
of primitive land-inhabiting insects living today (e. g., in the 
Ancistrogaster-like Dermaptera, in lampyrid larve and various 
other forms described in the Jour. N. Y. Ent. Soc., Vol. 24, p. 1) 
and are not gills at all, so that all of the available evidence points 
to a terrestrial life on the part of the first winged insects, during 
their immature stages, and many of them probably exhibited a 
hiding tendency—a trait which, in conjunction with the develop- 
