The genus Hecatesia was founded by Boisduval in 1829,* upon a singular Zygenidous insect sent to Latreille by Mr. Alexander Macleay, from New Holland, in some part of which it does not seem to be uncommon.

(Footnote.  Essai sur une Monographie des Zygenides page 11.)

The species H. fenestrata Boisduval (l.c. page 11 plate 1 f. 2) was brought by Mr. Hunter, Surgeon of Captain King’s expedition, and by him presented to the British Museum.  Another species has been described by the Baron Feisthamel in the voyage of the Favorite (page 19 plate 5 f. 1) under the name of H. thyridion.* Of this species there are specimens in the collection presented to the British Museum, and I take the present opportunity of describing the female of this species, only remarking that it wants the fenestrated clear space in the upper wing.**

(Footnote.  Lepidopteres nouveau, etc.  Supplement a la Zoologie du voyage autour du monde de la Favorite sous le commandement de M. Laplace capitaine de Fregate.)

(**Footnote.  At first, from the body being so much more slender than in the fenestrated specimens, I thought it might be the male but, on showing the specimen to Mr. Edward Doubleday, he pronounced it a female.

The H. thyridion is distinguished from the H. fenestrata by its larger size, and a third yellowish white interrupted band close to the base of the first pair of wings; the fenestrated spot is narrower, more lunated, and is much smaller in proportion than in the corresponding part in Dr. Boisduval’s species.  The body beneath is girded with four yellowish white and black bands, the black bands are continuous on the sides, while the white pass on the sides into the deep ochry-yellow of the upper side; the abdomen has a single row of black spots (at least seven) down the middle, one at the base of each segment, the two nearest the thorax have a whitish spot behind them.

The female of this species brought by Captain Grey has the upper wings more developed; the three interrupted whitish bands are composed, at least the two outer, of three spots, larger than in the female; the little bluish white spots on the deep brown part of the under side of the lower wing are also nearly obsolete; the sides of the body are not fringed as in the male; and the apical tuft is very small indeed.

The most marked character however is the want of the fenestrated diaphanous spot in the upper wing, which being a most prominent characteristic in the examples of this species already recorded, makes it highly probable that they have all been females, and that this is the first time that the male has been alluded to.

The beautifully striated and waved surface of the glassy spot, taken in connection with the fact of the noise made by the insects possessing it, would seem to indicate that the fenestrated spot must act as a tympanum.

Cossodes lyonetii, new species.  Illustration 26 Insects 9.