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given rise to one of the most harrassing nuisances in entomology. 
Species that are thought to be species by one individual, are duly 
described ; another worker sinks them under some other species, and 
in a few years the same thing is redescribed by someone else, and then 
later on it is found there are two names for the same individual. The 
priority rule says we should hold to the former name, and although 
the second may have been in use for years we compel ourselves to 
change it for the former. This is of course not all, we have to remember 
the other name as well if we want to read about our subject. You 
are, however, to hear a paper on synonymy, so I must not trespass. 
I have introduced it merely to show that it is of our own making in 
great measure through this varying standard of species rank. That 
the standard is varying is admitted pretty generally. Tutt says 
“ that there is no real distinction between races and species is certain, 
the matter often resolving itself into one of opinion; ” that the matter 
is only a case for opinion is true, so long as we do not insist on any 
one or more special traits being necessary to determine whether an 
insect has diverged sufficiently from others to rank as species. In the 
case of the two Tephrosias —bistortata and crepuscularia —the two 
Triaenas —psi and tridens —certain Anthrocerids and others, the amount 
of divergence is nothing like that in the large majority of our named 
species. Why then do we place them in the same rank ? If the one 
is being descended from the others, then the more fixed or older form 
is taking the rank of a genus, looking upon a genus in the genealogical 
sense. Then in turn that genus will be wholly unequal to the vast 
majority of the genera generally. We have been discussing a species 
when we know all about it; how difficult must it therefore be when we 
have only the imago! Cockerell says: “ The essential distinctions between 
species are physiological, the morphological ones being only valid so 
far as they happen to coincide with the physiological.” Tutt, falling 
in with this view says: “ Thus the two forms of Amphidasys betularia 
in spite of their external differences, cross freely in a state of nature ; 
whilst Anthroccra trifolii and A. lonicerae, although equally able to cross 
and produce fertile progeny, are specialised in a state of nature to 
some particular food-plant, habit and habitat, and are maintained 
distinct.” In the meantime, with the hosts of insects of which we 
know nothing of their life-history, we unfortunately have to totally 
rely on the morphological characters. The recent attention called to 
the genitalia, tends to show that we here may have a morphological 
character upon which to place some reliance. The character has the 
great advantage that as far as we can see is not influenced by any 
cecological cause. Although I am entirely with Cockerell in saying 
that the essential distinctions between species are physiological, I do 
not follow him in the second part of his remarks, namely, that the 
morphological ones are only valid so far as they happen to coincide 
with the physiological. I maintain that certain morphological 
characters are the entire result of the primary physiological distinctions, 
and are therefore every bit as valid. The insect, for instance, that is 
closely related to another, but specialised to a particular food-plant, 
will perhaps grow to a larger or less size, and if it were found by actual 
measurement that within certain limits the two forms kept to their 
own respective measurement, this could be taken as a specific 
value. The instance of size is perhaps not such a happy one as 
