122 Mr. G C. Griffiths on the 
seventy species examined, and his remarks as to these 
are for the most part correct and show careful observa- 
tion, though in one or two instances in which the organ 
is weakly developed it appears to have been overlooked 
by him. 
Kirby and Spence refer somewhat at length to the 
appliance but state that it is found “in many male 
butterflies, hawk-moths and moths.” Later observers, 
however, have determined that, as regards the Diurni, it 
occurs only in one or two species of the Hesperiide, 
which in some other respects partake of the characters 
of the Heterocera. Blanchard, indeed, has given the 
name Achalinoptera to the butterflies and Chalinoptera 
to the moths on account of the absence or presence of the 
apparatus, but this, as will presently be seen, is not of 
sufficiently general occurrence to be made use of as a 
discriminating character of such importance. Kirby and 
Spence refer rather unfortunately to the organ of the 
male as consisting of one o7 more bristles but add that 
the females often have the bristles, but never the hook. 
Burmeister in his “ Handbuch der Entomologie,” and 
Boisduval in the “Spécies général des Lépidopteres,” 1836, 
both refer at some length to the frenulum, as also does 
Prof. Westwood in his “ Introduction to the Modern 
Classification of Insects,’ 1838. 
Dr. Chenu in his “ Encyclopédie d’Histoire Naturelle ” 
(Vol: Papillons Nocturnes, by EK. Desmarest) mentions 
the organ, but assigns as its object the maintenance of 
the wings in a horizontal or an inclined position during 
repose. 
It will be evident from the above that the accounts of 
the frenulum as given by various authors differ both as to 
its development and its purpose. 
In commencing an examination of the subject several 
years ago this was brought strongly under the notice of 
the writer at the outset, and it seemed that much might 
still be learned from a study of the appliance in a large 
number of examples extending over the various groups 
and genera of the Heterocera. Accordingly an examina- 
tion, either microscopic or by means of a platyscopic lens, 
has been made of the majority of our British moths, in- 
cluding the so-called Micro-lepidoptera, and of several 
hundred species of exotic Heterocera. The results of this 
investigation are here recorded. 
