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Walking Sticks

(Family Phasmidae.)

The insects of this family present some of the most striking forms known among the Hexapoda. They consist of the so-called "walking sticks." This name is given to them from the remarkable development of protective resemblance which has brought all of the species to a close imitation of the twigs of different plants. The family reaches its highest development in the tropics, but one species is common in the Northern States. The family constitutes the section of Orthopterous insects known to the old naturalists as Gressoria or walkers, as contrasted with the runners, jumpers, and graspers (Cursoria, Saltatoria and Raptoria). The body is long and slender, the head is exserted, the legs are long and slender and generally similar. They generally have no wings although some of the tropical species have short or long wings. The eggs have a very curious structure and frequently resemble seeds in appearance. They possess the power of reproducing lost limbs, the new limb being weaker than the old one and generally curved. Certain of the tropical forms in this family are curiously modified so as to resemble leaves instead of twigs. Leaf insects in the tropics frequently bear so close a resemblance to vegetation as to deceive a keen observer.

Life History of a common Walking Stick

(Diapheromera femorata Say.)

This is the common "walking stick" of the northern United States and is distributed over the greater part of the country. It has been given the popular name of the "thick-thighed walking stick" owing to the fact that the femora of the middle legs are somewhat swollen. The eggs, of which each female lays about one hundred, are a little less than 3 mm. long, oval in shape, slightly compressed at the sides, and of a polished black color with a whitish stripe on one side. They resemble the small plump seeds of some leguminous plant. They are not laid in clusters or fastened to the plant but are dropped loosely on the ground where they remain through the winter and hatch the following May. Some of them are retarded in their hatching and young walking sticks may be found throughout the summer. In hatching the top of the egg lifts up like the lid of a vessel. The young when first hatched are 4.5 mm. long, and of a uniform pale yellowish-green color. They live, as a rule, near the ground and drop readily when disturbed. They molt but twice, retaining the same color until maturity, and develop rapidly, averaging, under favorable circumstances, about six weeks from birth to maturity. When adult the green color becomes gray and brown. This change in color is protective since in the early summer while vegetation is green, the insects are also green; when the foliage turns in the autumn they change color to correspond to a certain extent, and when the foliage is stripped they closely resemble the twigs upon which they rest. The front legs of the insect are stretched out straight in front so as to increase the twig-like appearance. The males are smaller than the females and frequently retain the green color in the mature condition, following the rule which holds more or less throughout nature, that the male sex is not so well protected as the female, since upon the latter depends the all-important function of reproduction. There is but one generation annually and, as before stated, the insect hibernates in the egg state on the surface of the ground. In spite of the protection afforded by form and color the insect seldom becomes sufficiently abundant as to be ranked as injurious although it feeds voraciously upon the leaves of plants during all stages of growth after hatching. In the few instances where it has become sufficiently abundant to do noticeable damage it has been easy to reduce its numbers to a minimum by burning over the leaves on the ground during the winter time, thus destroying the hibernating eggs. In 1898 this insect appeared in extraordinary numbers in a black-walnut forest in western New York, so that in the autumn the dropping of the eggs on the leaf-covered earth sounded like a heavy shower of rain.