Sub-class, PHALÆNÆ (central). Characters from larva, pupa, and imago. All varying (the universal character of such central groups). [Illustration: GENERA OF THE NATURAL ORDER COSSI.] Natural order, COSSI. Characters from the larva and pupa. Larva depressed, kaned; has sixteen feet, lives through one or more winters, never rolls itself in a ring when touched, feeds on the solid interior woody parts of vegetables; pupa changes in a tough cocoon, in which are interwoven particles of the larva's food; it has a double row of small raised denticulations on each segment of the abdomen, which give it partially the power of locomotion. Family ÆGERIIDÆ, Stephens. Characters from the Imago. Palpi triarticulate, incrassated at the base, acuminate at the apex, prominent, enclosing the antlia; antennæ, sub-cylindric, gradually incrassated from the base nearly to the apex, the apex itself acuminate and terminated with a fascicle of hairs; ocelli, two. Flight diurnal in the hottest sunshine. Genus MEMYTHRUS.--_Sphinx_, Linn.; _Sesia_, Laspeyres; _Ægeria_, Fab. Characters from the imago. Palpi very prominent, and densely clothed with scales at the base, in appearance angulated; antlia fine, not so long as the antennæ; antennæ the length of the thorax, in the male much pectinated, in the female simple; superior wings clothed with scales, inferior hyaline. Sp. 1. MEMYTHRUS VESPIFORMIS.--_Sphinx Vespiformis_, Linn. Syst. Nat. II. p. 804, n. 31. _Ægeria Asiliformis_ of Fabricius, and other authors. Characters from the imago. Palpi black, yellow at the apex; antennæ black, beneath testaceous; fulvous at the base; head black, excepting a white mark before each eye; a yellow ring round the neck; thorax black, with a yellow spot at the base of each superior wing; abdomen black, slightly barbate, with three equidistant yellow belts; superior wings deep fuscous, inferior hyaline; femora and anterior tibiæ black, posterior tibiæ and all the tarsi yellow. Inhabits England, but is very rare. Sp. 2. MEMYTHRUS CRABRONIFORMIS.--_Sesia crabroniformis_, Lasp. Inhabits Italy. Sp. 3. MEMYTHRUS CRASSIPES.--_Sphinx crassipes_, Drury. Inhabits Africa. Sp. 4. MEMYTHRUS TIBIALIS.--_Ægeria tibialis_, Fab. Sp. 5. MEMYTHRUS ----?--Unnamed in the Linnæan cabinet. Several other species probably exist, with which I have not happened to meet. The principal distinctions between Memythrus and Ægeria are, that the antennæ in the former are not longer than the thorax; in the latter they are much longer; in the males of the former genus they are decidedly pectinated, in those of the latter but obscurely ciliated; in the former the anterior wings are always opaque, in the latter always hyaline. _Natural Divisions to which the_ SPHINX VESPIFORMIS _of Linnæus is referable._