344 
Mr. J. W. Tutt on recent papers on 
arrived at. No scheme based on a single set of charac- 
ters, belonging to only one stage, can possibly be even 
approximately perfect. It is possible to conceive that, 
especially in those Orders where the method of life differs 
so greatly in the various stages and different means of 
defence and protection are thus rendered necessary, an 
insect may be very greatly modified in one particular 
stage, without any corresponding modification in the 
other stages being at all necessary. It may happen to 
be of advantage for the larva to be of a generalised type, 
and for the imago to be much more specialised, or vice 
versa. If this be granted, it follows that no scheme of 
classification that is not founded upon a consideration of 
the structural details and peculiarities of the insects in all 
their stages can be considered as really sound, or as 
founded upon a natural basis. It is also evident that 
the results of the various systems — whether based on 
oval, larval, pupal, or imaginal characters — must be com- 
pared, and the sum total of evidence brought together, 
if a satisfactory result is to be obtained. If these results 
agree, then it is clear that the conclusions arrived at are 
sound; but if the characters from one stage appear to 
suggest a different result from those obtained from 
another, it is evident that fresh observations and com- 
parisons need to be made, and the differences to be 
explained before any adequate scheme can be reached. 
It is with a view of comparing, in some small degree, 
the results arrived at by Dyar (using larval characters), 
by Chapman (using pupal and larval characters), and by 
Comstock and Hampson (using imaginal characters) that 
the following notes are offered. 
As is well known, in many Lepidoptera the wings are 
united by a " frenulunl,^^ or bristle, which is single in the 
male, but frequently more complex in structure in the 
female. This frenulum arises from the base of the costa 
of the hindwing, and articulates with the retinaculum on 
the underside of the forewing. In the Hepialidse and 
Micropterygidse the wings are united by a " jugum,^^ or 
membranous lobe, which arises from near the base of the 
underside of the forewings. This jugum holds the base 
of the costal margin of the hindwing, as it were, in a 
vice, between itself and the inner margin of the fore- 
wing, a condition very similar to what obtains in the 
Trichoptera. These organs (the jugum and the 
