Why this species, and doubtless many others of its family, are thus favored, will soon be apparent. Ants may be seen wherever these larvæ may be found, ever ready to receive the honeyed secretion when it pleases the little creatures to eject it, but all the while exercising the closest vigilance lest some wary ichneumon may come along and deal a thrust of its ovipositor, which means misery and ultimate death to their helpless friends. So intent is the larva, with its head buried in the flower, upon its feeding, and so quietly and stealthily does the ichneumon approach its intended victim, that hardly a single individual would be left to tell the story of its existence were it not for the ants. The larvæ know their protectors, it would seem from their actions, and are able and willing to reward their services. The advantage is mutual, and the association friendly. No compelling by rough means on the one part is noticeable, and no reluctant yielding on the other. All demonstrations made by the ants are of the most gentle character. They caress, entreat, and as they drink in the sweet fluid, lifting their heads to prolong the swallowing, they manifest to the utmost their satisfaction and delight. It is amusing to see them lick away the last trace, caressing the back of the segment with their antennæ as they do so, as though they were coaxing for a little more.
In Pseudargiolus the tubes are white, cylindrical, nearly equal in size, rounded at summit, and studded with little tuberculations from which arise the tentacles. These last are tapering, armed with small spurs set in whorls, and stand out straight, making a white hemispherical dome over the cylinder, but none of them fall below the plane of the base of the dome, nor do they ever hang limp or lie across the dome, as is the case in a European species. When the tube comes up the rays rise in a close pencil, and take position as the dome expands; but, on the contrary, when the tube is withdrawn, the top of the dome sinks first, the rays coming together in pencil again.
VIOLACEA BUTTERFLY.
Larva, Protected by Ants, Feeding on Flower-buds of Dogwood.
Lycæna pseudargiolus is subject to great variation, and occurs under many forms, most of which having been regarded as distinct species. In the early spring Violacea appears, and is characterized by dimorphism in the female, some of that sex being blue, others black. This form, which may be called the winter form, deposits its eggs in the clusters of flower-buds of the Dogwood, the young larvæ obtaining their first food by boring into the buds, but later on eating their way into the ovaries. The flies that come from these larvæ late in May are Pseudargiolus, which, as stated before, lays its eggs on Cimicifuga racemosa, most of the resulting butterflies over-wintering to produce Violacea. A small percentage of the May chrysalids give butterflies as late as September, which are smaller than the parent-form, and also differ therefrom in the more decided character of the marginal crescent discal spots on the under side of the wings. There does not seem to be any regular second summer brood, that is, there are but two regular annual broods, the Violacea of March and the Pseudargiolus of May, the individuals happening to emerge in July, August and September being irregular visitants, for which the name of Neglecta has been given. The females of the last form lay their eggs upon Actinomeris squarrosa, and the chrysalids, thence resulting, give Violacea the next spring.
Larvæ feeding on Dogwood vary much in color from those that feed on the Black Snakeroot, few being white in the last stages, but nearly all dull-crimson or green, or a mingling of the two. Nevertheless, a small percentage of the larvæ on Cimicifuga racemosa are also green or crimson, though the most of them white. Ants do not seem to visit the larvæ on the Dogwood, and on being introduced to them in confinement treat them with indifference. On rare occasions tubes have been discovered in the eleventh segment, fully expanded, and accompanied by a pulsating movement, but no teasing or irritating availed to make them appear. Even severe pressure applied to the sides of the segment failed to force out any fluid. As with the fall food-plant, Actinomeris squarrosa, the Dogwood is neither sweet nor juicy, and it is possible that the larvæ feeding on these plants do not secrete the fluid.
Eggs of this polymorphic species are round, flat at base, the top flattened and depressed, and have a diameter of one-fiftieth of an inch. Their ground-color is a delicate green, the entire surface being covered with a white lace-work, the meshes of which being mostly lozenge-shaped, with a short rounded process at each angle. In from four to eight days the egg hatches into a larva, which is scarcely one-twenty-fifth of an inch long, and whose upper side is rounded, the under being flat. On each side of the dorsal line is a row of white clubbed hairs, with similar ones at the base and in front of the second joint, making a fringe around the body. The head is very small, obovoid, retractile and black; the legs retractile, and the color a greenish-white or brownish-yellow.
The first moult occurs in from three to five days, the larva having increased to twice its former length, while very little difference is manifest in the coloration. In from three to five days the caterpillar has again changed its skin, doubled its length, assumed more pronounced colors, which are diversified in some with mottlings upon back and sides, and developed along the back, from the third to the tenth joint, a low, broad, continuous, tuberculous ridge, cleft to the body at the junction of the segments, the anterior edge of each joint being depressed, the sides incurved. The third moult takes place in three or four days more, but there is very little change from the former period. Three or four days subsequent to this change occurs the fourth or final moult, and in five or six days from this the larva is ready to pass into the chrysalis state.
In its mature form the larva is about one-half of an inch in length. The body is onisciform, flattened at base, furnished with retractile legs, and has the back elevated into a rounded ridge, which slopes backwards from the sixth segment. The sides are rather deeply hollowed, and in the middle of each segment, from the third to the eleventh, is a vertical, narrow depression. The last segments are flattened, the last of all terminating roundly, its sides being narrowed and slightly incurved, while the second segment is flattened, arched and bent nearly flat over the head. Standing on the body is a ridge, tubercular in nature, which in each segment from the third to the eleventh is distinct and cleft to the body. In color, specimens vary. Some examples are white, others decidedly greenish, but many have the posterior slope of the second segment black or dark brown, while a few have most of the back a dark brown, irregularly mottling a light ground, or with small brown patches diffused over the back, but mostly on the anterior segments. The entire surface is velvety. This appearance is caused by minute stellate glossy processes, scarcely raised above the surface, mostly six-rayed, and sending from the centre a concolored filamentous spine a little longer than the rays. These stars are arranged in nearly regular rows, and are light, except in the brown patches, where both star and spine are brown. This velvet-like condition of the skin only reveals its true composition under a magnifying glass.
On the eleventh segment, near the posterior edge of the back, is a transverse slit, in a sub-oval spot, from which proceeds a membranous process; and on the twelfth, on each side, is a mark like a stigma, but a little larger, from which proceeds a membranous tube, ending in a crown of feathery tentacles, these three special organs being exposed or concealed at the will of the larva. The head is small, obovoid, dark brown, and is placed at the end of a long, pale green, conical neck, which is rectractile, both neck and head being covered by the second segment.