GENUS. SPILOSOMA, _Stephens_. Arctia p. _Schrank_. Eyprepia p.
_Ochsenheim_. Bombyx p. _Fabr._
SPILOSOMA ACREA. Alis niveis (postieis [male] fulvis), punctis nigris,
costalibus majoribus; abdominis dorso fulvo nigro maculato. (Expans.
Alar. [male] 2 unc.--[female] 2¾ unc.)
SYN. [female] Phalæna (Bombyx) Acrea, _Drury, App. v._ 2.
[male]. Phal. (Bomb.) Caprotina, _Drury, App. v._ 2.
Bombyx Acria, _Fab. Ent. Syst._ III. 1. _p._ 451. _No._ 137. _Abbot and
Smith, Ins. Georg. tab._ 67. (exclus. _Syn. Fabr._ B. lubricepidæ).
Arctia Pseuderminea (_Peck_), _Harris in Massachus. Agricult. Repos.
vol._ 7. _p._ 328. _and tab. annex_.
HABITAT: New York, Maryland, Virginia (_Drury_).
MALE..--_Upper Side._ The antennæ and eyes are black; the thorax and
extremity of the body cream colour; he abdomen yellow, spotted on the top
and sides with black. The anterior wings are cream coloured, spotted with
black. The number of spots very uncertain, except five which are placed
on the anterior edge, and six on the external one. The cilia yellow, as
are the posterior wings, on each of which are three black spots, two near
the external edge, and one near the middle.
_Under Side._ The breast and thighs are yellow; the abdomen and legs the
same, chequered and spotted with black. All the wings are yellow, spotted
in the same manner with black, as on the upper side.
FEMALE.--_Upper Side._ The head and thorax white. The abdomen yellow,
with black spots on the sides and top, the extremity being white. All the
wings are white, with black spots, whose number is very variable; but, on
the anterior edges of each anterior wing, are placed five, and on the
external edges, six.
_Under Side_. The legs are black and white, the thighs yellow; the
abdomen white, spotted with black. All the wings are white, with black
spots, most of which, observed on the upper side, being seen on this.
This species is closely allied to the common British species, Spilosoma
lubricepida, and Menthrastri; but is of larger size, the spots being also
larger. The two figures given by Drury, are now ascertained to be the sexes
of the same species, as, indeed, our author had surmised might be the case.
It appears to be a very common species, and is stated by Drury to breed
twice a year, namely, in June and September. The caterpillar is very hairy,
and when young is white; as it advances in age, it acquires a fox colour,
and, in its last skin, becomes almost black. Dr. Thaddeus W. Harris, a
distinguished American entomologist, to whom I am indebted for many
valuable insects of that country, has published a very interesting notice,
in the work above cited, upon this insect, under the title of "The Natural
History of the Salt-marsh Caterpillar," under which name the larva of this
insect is commonly known, and which is exceedingly destructive to grasses
of various kinds. He states, that when nearly full-fed, "they become very
voracious, and continue eating all the day and night without intermission.
Soon they leave the meadows, aggregated in great numbers, and commence the
wandering state, or begin to run, as is the phrase, devouring everything in
their progress; corn-fields, gardens, and even the coarse and rank
{8}produce of road sides, afford them temporary nourishment, until they
have found a place of security from the wind and weather." Dr. Harris, in a
communication to me, has stated, that he had ascertained that this insect
was the Acria of Fabricius, and that Professor Peck's name must, therefore,
be rejected. Abbot observes, respecting this caterpillar, that it is "a
general devourer of all field and garden-plants, and weeds. It spun up in a
thin web, intermixed with its own hairs, on the 16th of May, and the moth
came out on the 2d of June. Others of the autumnal brood, taken in
September, spun up on the 18th of that month, and remained in the chrysalis
until the 21st of April."