Butterflies - The Tribe Of The Yellows
( Originally Published 1917 )
The Brimstone or Cloudless Sulphur
Practically all northern butterflies are variously marked in different colors, while the butterflies of tropical regions are commonly tinted in monotone, though often showing a splendid iridescence. One with very little experience can tell the look of a tropical butterfly and would be likely to say at once that the Cloudless Sulphur is one of these. The upper surface of the wings of the male is a clear plain sulphur with merely the narrowest possible fringe of brown around the margin made only by the colored marginal scales. The under surface is lighter and sparsely dotted in brown. In the females the marginal brown takes on the shape of a series of small crescents and there is a single round brown eye-spot just in front of the middle ofeach front wing.
While the Cloudless Sulphur is without doubt essentially a tropical species it has an extraordinary geographical range. It is extremely abundant in Mexico, Cuba, and the tropical zone in South America. It extends south even to northern Patagonia and north to New England, Wisconsin and Nebraska.
Presumably in the tropics this species breeds continuously, one generation following another in regular succession unless interrupted by drought or other natural phenomena. In our Southern states there is more or less interruption by the winter season, so that it is commonly considered to have only two broods, the butterflies hibernating. Farther north there is probably only one brood in summer, and perhaps not even that in the extreme limit of its range. For there is pretty good evidence that the specimens seen in the Northern states are migrants from the south, comning singly or in scattered flocks in early summer, and if they lay eggs the butterflies of the new generation return south in autumn. But the precise conditions are not well known and need careful observations in various localities.
The life story of a generation of these butterflies is much like that of the other Yellows. The eggs are laid, one in a place, on the leaflets of various species of wild senna (Cassia) and soon hatch into cylindrical caterpifiars that devour the tender leaflets. In a few weeks the caterpillars mature and change to curious and characteristic chrysalids. The head projects in the shape of a cone and the back is so concave as to give the side view of the chrysalis a very striking appearance.
Like so many of the Yellows this butterfly is sun-loving and social in its habits. Great numbers flock together, their large size and bright coloring rendering them very conspicuous. They often alight on the ground to sip moisture when they have been likened to beds of yellow uses. They also fly long distances in flocks that at-tract much attention. It is likely that the northward distribution takes place in summer through such migrating hosts.
Other Sulphur Butterflies
The Large Orange Sulphur is a closely related butter-fly of about the same size, in which the coloring is uniformly orange yellow instead of lemon-yellow. It also belongs to the tropics, occurring in our extreme Southern states and ranging occasionally as far north as Nebraska.
The Red barred Sulphur is another splendid butterfly, somewhat Iarger than the Brimstone, which is easily distinguished by the broad reddish bar across the upper surface of the front wings. It is tropical but migrates rarely even as far north as Indiana, Illinois, and Wisconsin.
The Dog's-head Butterfly
The Dog's-head butterfly furnishes one of the most remarkable examples of accidental resemblance in wing markings that can be found in the whole order of scale-winged insects. It is comparable with the skull and crossbones on the back of the death's head moth. In the butterfly the middle of the front wings has a broad band of yellow against a black margin on each side and the yellow outlines make an excellent silhouette of the profile of a poodle with a large black eye-spot in exactly the proper place. The females are less brightly colored than the males but they still show the dog's-head silhouette.
This is a southern species, which occasionally strays as far north as New York City, New Hampshire, Wisconsin, and Iowa. The larvae feed on species of Amorpha and are believed to be three-brooded in southern regions where the butterfly occurs.
The California Dog's-head is even more beautiful than the southern species. It is remarkable for its pink and purple iridescence a characteristic which is not common in the butterflies of the Yellow and the White Tribes. The silhouette of the Dog's head is less perfect than in the more eastern species, and the yellow color tones are more tinged with orange, The female is strikingly different, the wings being plain pale yellowish buff marked only with a round blackish eye-spot near the middle of each front wing and the barest suggestion of a dark line around the extreme margin.
The Clouded Sulphur
It is an interesting fact that the butterfly which one is most likely to find in fields and along roadsides during practically all the weeks of summer has seldom if ever been noted as a destructive insect. The Clouded Sulphur is probably the commonest species in its group. There may be times when the White Cabbage butterfly or other forms are more abundant, but the Clouded Sulphur retains its place season after season, with comparatively little noticeable variation in its numbers. This is doubtless an illustration of an insect which has established such relations with its food plants and its various insect and other enemies that it remains in a fairly stable equilibrium an example of what is often called the balance of nature.
The Clouded Sulphur is about the only medium-sized yellow butterfly generally found in the Northeastern states. The adults may be seen from spring until autumn. They lay eggs upon clover and other plants. These eggs hatch into small green caterpillars that feed upon the leaves and are protectively colored so they are comparatively seldom seen. When the food plant is disturbed they drop to the ground, crawling up again upon stems and leaves when the disturbance is over.
These caterpillars moult several times during their growth. When full grown they find such shelter as they are able and each spins a silken web over part of the surface. It then fastens its hind legs into this web and later spins a loop near the front end of the body. It pushes it-self beneath this loop and waits for several hours before the skin breaks open along the back and is gradually shuffled off revealing the chrysalis in position. A week or two later the fully developed butterfly emerges from the chrysalis.
These yellow butterflies lend a distinctive charm to our summer landscapes. They are constantly to be seen fluttering from place to place, lightly visiting flowers of many kinds from which they suck the nectar, and gathering in great colonies by roadside pools where they seem to sip the moisture. There are many references to this insect in the writings of New England authors. It evidently was an especial favorite of James Russell Lowell who has often referred to it in passages like this:
"Those old days when the balancing of a yellow butterfly over a thistle bloom was spiritual food and lodging for a whole forenoon."
The Orange Sulphur
Were one able to take a Clouded Sulphur butterfly and change the yellow to a deep orange color he could easily make a specimen that would pass for the present species. The resemblance is very remarkable and shows the close affinity between these two beautiful insects.
Like so many others of this group the Orange Sulphur is essentially a tropical species. In the eastern United States it is rarely found north of latitude forty degrees, but south of that it becomes increasingly abundant as one approaches the tropics. It occurs from the Carolinas to Texas, and over the great range in which it lives it takes on many different forms and habits. It is one of the most remarkable examples of variation in coloring exhibited by any of the butterflies. Nearly a dozen species names have been given to its various disguises, all of which are now recognized as synonyms. In the more northern regions where it is found, only one of these forms usually occurs, but in other places bright yellow and pale white varieties are found.
The life-history of this butterfly along latitude forty degrees is very similar to that of the CIouded Sulphur. There seem to be usually two broods and the caterpillars live upon leguminous plants, especially alfalfa, buffalo clovers, wild senna, and other species of Trifolium and Cassia. Apparently also it hibernates in both the caterpillar and the butterfly stages.
In the extreme Southwest as on the plains of Texas the vegetation dries up completely in summer so that there is no succulent leafage for the caterpillars to live upon. In such cases the insect must aestivate rather than hibernate. This species apparently succeeds in doing this by having the caterpillars go into a more or less lethargic condition in which they pass the summer. The adult butterflies utterly disappear in June and are not seen again until any in autumn when the autumn rains have; started the growth of vegetation anew. The insects then make up for lost time and produce several broods in rapid succession.
In the Imperial Valley of California this butterfly is a serious pest to alfalfa growers. It continues to reproduce throughout a very long season, one brood following another from March until December, and in mild winters there seems sometimes to be practically no cessation of its activities. Mr. V. L. Wildermuth found that the development of a generation in breeding cages in this valley varied from twenty-two to forty-four days, the latter in cool, the former in hot weather. The stages' in the first and the third broods in spring varied thus: Egg, first six days, third four days; larva, first thirty days, third twelve days; chrysalis, first eight days, third five days. In this case the first generation extended from March 15 to April SO and the third from May 28 to June 20. After the fourth brood of butterflies there was such an overlapping of the various stages that it was impossible to distinguish the broods.
The Pink-edged Sulphur
Eurymus interior This beautiful butterfly was first made known to the world of science by Louis Agassiz, the great naturalist who did so much to arouse a scientific interest among Americans. Ile found it on a famous expedition to the northern shores of Lake Superior, which not only served to bring to light many interesting phases of geological history but also laid the foundation for the copper mining industry which has since become so important in that region. The butterfly thus brought to light has been found to be a characteristic northern species, occupying a rather narrow belt nearly along the fiftieth degree of latitude and extending west almost to the Pacific Coast. The species is occasionally taken as far south as the White Mountains and there are indications that in this region there are two broods a year. The male butterflies are known at once by a beautiful pink edge on all the margins; they bear otherwise a close resemblance to our common Sulphur Yellow. The females are much lighter in color, often having no black markings on the upper surface of the hind wings.