42 
number of pectinations or any other direction. The 5 moth that sits 
on the tree trunk, one is justified in supposing, is not so easily brought 
to the notice of the male as one that can fly, and hence the antennae 
are brought into the question. Other characters of the imago might 
be cited in the same way. The labial palpus, for instance, is no doubt 
a plastic structure depending on the value or use, in very many cases, 
that an insect makes of its proboscis. It is quite possible to 
imagine that an insect, isolated from its habitat of ages where certain 
plants grew, might be set down in a place where different plants grew— 
plants different in form, which would call for a greater or less length of 
proboscis. In those cases where the palpi are used to protect the 
proboscis, a large palpus would be necessary to encase a large 
proboscis. Protection cannot, however, be the sole use in such 
instances as in the Libytheinae, but it doubtless plays its part, and a 
large part. But although we can arrive at some conclusion for the 
non-acceptance of the above organs for family distinction, we cannot 
use others because they do not offer, or seem to offer, any sort of rule. 
Such are the spines on the legs and the rows of hairs round the eyes. 
The latter character, made use of by Meyrick in his Handbook of 
British Lepidoptera, shows one at what grave errors we can arrive 
by studying one side of the question only. If we can discover an 
imaginal character that will coincide with our idea of classification by 
the embryological stages, so much the better, and it is earnestly to be 
hoped that whatever the faults to be found with neuration to start 
with, we shall soon be able to understand and use the nervures for the 
location of species into families at least. To go beyond this and to 
use neuration for the definition of genera, is a total defeat of the great 
claim for it, namely, its immutability by external forces. As I shall 
later attempt to show, the characters of genera should be much more 
easily affected by external forces than those of families, and the 
greater the subdivision one makes the more so is this true ; specific 
characters being more mutable than generic ones. 
1 cannot leave the subject of neuration without calling attention 
to some of its values if even in the present imperfect state of our 
knowledge concerning it. Many, the vast majority of our Noctnidae, 
for instance, have now been bred, and in every case the neuration of 
the perfect insect lias similar, often identical, neuration. With such 
constancy as this, we are pretty safe in assuming that nearly every 
insect with noctuid neuration is a Noctuid. In the key to the families 
set forth by Hampson to vol. i of his Lepidoptera Phalaenae, other 
imaginal characters are brought in when neuration fails to separate 
groups, and we have the frenulum, the palpi, and the antenme all 
playing a minor share in conjunction with the neuration as the base. 
Thus every moth having in hindwing vein 10 absent and with 8 
removed from 7, 8 anastomosing near base only, vein 5 nearer 4 than G 
in forewing, and with a frenulum, and with antenme with shaft not 
dilated; must be a Noctuid. In point of fact to the working 
entomologist who knows the appearance of a Noctuid, the rein 8 remote 
from 7 and also 8 anastomosiny near base only , would not be attended 
to because the only family imaginally with which one would be likely 
to confuse with Noctnidae, would be the Geometridae , which also has 
the above conditions but which is immediately separated by its not 
having the frenulum. A very remarkablo instance of the value of 
