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§ V. On Scent-organs on the Legs of certain Lepidoptera 
[Supplement ), 1 
Plate D. 
I concluded my notice on the odoriferous organs which distinguish 
certain male butterflies, by saying that the subject promised a harvest of 
new and interesting facts. It appears to me to be, in fact, an inex¬ 
haustible mine. Scarcely a fortnight has passed and I am able to add 
to the structures described in that paper two others— and these the most 
singular I have encountered among our Lepidoptera—found in the males 
of two species of Erebid moths. 
One of them is a dwarf in this family of giants, whose expanse, with 
open wings, does not exceed 4 centimetres. In some species of the same 
family, as in various Hesperidae (. Achlyodes , Antigonus , etc.), the scent- 
organs consist of a tuft of long hairs rising from the base of the hind 
tibiae. The organ in these species of Erebids presents a similar form, but 
arises from the base of the anterior and not of the posterior tibiae. The 
tuft is composed of black hairs, whose length (4 mm.) exceeds that of the 
tibiae (2 mm.), as also of the femora (3 mm.). Just as in some Hes¬ 
peridae , the scent-tuft of the hind legs is hidden between the hind coxae 
and the base of the abdomen, so in the Erebids in question it is appressed 
lengthways along the under side of the femur, whose margins are bordered 
with pale hairs, forming a sort of case for the tuft (PI. D, Fig. 1). The 
front tibia can not only be extended so as to form a straight line with the 
femur, as is observed in other Lepidoptera, but can go even beyond this 
(Fig. 2) ; and it is by means of this excessive extension, that the scent- 
tuft is unsheathed or drawn out of its case, being at the same time erected. 
In the second species, whose expanded wings measure about 6 centimetres, 
the scent-organs occupy the femur of the second or middle pair of legs. 
These organs are most interesting, not so much on account of their 
unusual position as for their size, and for their verily monstrous propor¬ 
tions, forming as they do a kind of ball, a globose or ellipsoidal body, whose 
diameter equals the length of the femur (PI. D, Figs. 5, 6, 7). Neither in 
the front nor in the hind legs (Fig. 3) is there any difference between 
the two sexes of the species : the intermediate legs of the male, on the 
contrary, not only exhibit the profound modification of the femur, due to 
the development of the scent-organs, but are also distinguished from those 
of the female (Fig. 4) by the greater length of the first tarsal joint. The 
1 Archivos do Museu National do Bio de Janeiro , II. (1877), pp. 43-46. By Dr. 
Fritz Muller, Travelling Naturalist for the National Museum. 
