True Tales of the Insects
ISO TRUE TALES OF THE INSECTS.
rush from their den, seize a locust, and hurry it headlong down their gloomy hole, never again to see the light of day. Ants, mantidae, dragon-flies, and others, doubtless do their part in helping to keep the locust in check.
Fastening themselves to it, under the wings, the Locust Mites suck the carcase to a dry shell, the dead bodies of the locusts sometimes almost covering plants, where they have taken hold of a leaf or stalk, and clasped it with a dead embrace; while others fall to the ground to die.
The enemies of the locust so far mentioned either devour it bodily, suck its juices, or are parasitic upon it externally. There remain those which prey upon it internally, the most numerous and beneficial of which are the larvx of the Tachina-flies. These attach their eggs to the parts of the body not easily reached by the jaws and legs of their victim, so as to prevent the Qgg from being detached. The locusts are attacked on the wing, and one haunted by a Tachina-fly makes frantic efforts to evade the enemy. But the fly persistently buzzes around, waiting her opportunity, and when the locust flies or hops, darts at it and attempts to fasten her fails, but^gg under the wing or on the neck. Often she perseveres until usually her task is accomplished. The larvae that hatch from these eggs eat into the body of the locust, and after living for a time on its fatty parts, issue and complete their metamorphoses elsewhere. A locust infested, though enfeebled, seldom dies till the
maggots have left. So efficient is this parasite in America, frequently the ground is covered with locusts dead and dying from this cause; and in this manner whole swarms are rendered harmless. It will be remembered that the constant annoyances of these Hies were suggested as at times one of the immediate causes of locust migration. In warm weather, the flies multiply rapidly, pass-incr throuofh their transformations in the course of a
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P"iG. 23. Methoiic (iJiJerssoni, specially remarkable for its comiilex organs for producing sound.
fortnight; but in the cooler seasons the development under ground is delayed, the winter being usually passed in the puparium. Kunckel d'Herculais finds that Staurojiotiis niaroc-caniis and other Aridiidse are followed on their devastating march by viviparous Diptera, which deposit their larvce in the bodies of the locusts, the parasitism of these larvse resulting in a sort of rachitic condition, answering to that produced by the Tachina-flies on the Rocky Mountain Locust. It is an odd and interesting
fact that not a single member of the great family is known essentially parasitic—Ichneumonidae—insects to attack the locust, either in Europe or America.
Some Species of Acridiidcc Present an Umisiial Aspect.
The very large number of species of Acridiida; have been recently arranged in nine tribes. Although the migratory locusts, just considered, and, indeed, the majority of this great host, are readily recognized from their family resemblance as belonging to the group, there are others that present an unusual aspect. Such is speciall)- the case with the members of the tribes Proscopides, Tettigides, and Pneumorides, and with some of the wingless forms of the Oedipodides, a species of which we figure. The tribe Proscopides (see Fig. 21) includes some of the most curious of the Acridiidse. Of their metamorphoses, which are probably trifling, we are ignorant; of their habits we know little. Their colours are sober and dull, and Breitenbach describes the finding of some in abundance which he had overlooked for a long time, since they exactly resemble the withered vegetation amongst which they sit. When alarmed they seek safety with a lengthy and " lightning-like " leap. Their general resemblance to Phasmidse, or Stick Insects, is striking.
But although the linear form and the very long body are common to both, this structure is due to the development of different parts in the two families. In Phasmidse the prothorax is short, the mesothorax elongate, while in Proscopides the reverse is the case. The great length of head is very curious in these insects; but the mouth is not thereby brought nearer to the front, but is placed on the lower side of the head, quite close to the thorax. In most cases the sexes differ strongly from one another, and both usually are entirely apterous. But the genus Astroma displays a remarkable exception, and an almost unique condition of the organs of flight, the front wings being absent in each sex, while the female has rudiments of the hind pair which are wanting in the male. Of the tribe Tryxalides, Tryxalis pharaonis, Klug, (see Fig. 19) is a handsome species, found in Sicily, Egypt, Algeria, Caucasus, and Andalusia. This insect approaches the Proscopides in form of the head and other characters. The tribe includes a great many species of grasshoppers. It and the Acridiides are the most numerous in species of the family; and to the latter belong most of the migratory locusts of the New World. We come to the tribe Tettigides, a very extensive group of small Acridiidce, remarkable for the shape of the pronotum, which is prolonged backwards as a hood
r34 TRUE TALES OF THE INSECTS.
reaching to, or beyond, the extremity of the body. In our British species this hood does not greatly modify the appearance of the insect, but in many exotic species, as in Xerophyllum, it assumes a grotesque form, so that the insects have no longer the appearance of Orthoptera, and when the genus Xerophyllum was for the first time described, it was mistaken for a buo-. There is an immense variety of forms of this extraordinary prothoracic expansion. The odd Cladonotiis Juimbcrtianus is a native of Ceylon, where it frequents sandy meadows after the fashion of our indigenous species of Tettix. Strange to say, some of these curious Tettigides, of the genus Scelimena, are amphibious in habit. They live on the borders of streams and ponds, and frequently dash on the water, and leap on their hind legs and flutter with their wings. In this way they strike the water without getting very wet; nor do they fear to enter the water, and leap about there; indeed it is said they prefer submerged plants as food. This singular habit has been observed in Ceylon and the Himalayas. The species have the hind legs provided with foliaceous dilatations probably suitable for swimming. These insects also frequent the little streams of water which trickle along the rocks, being often found clinging to a rock entirely immersed, as though they were enjoying a bath. The tribe Pneumorides includes a small number of
species of very aberrant and remarkable grasshoppers, peculiar to South Africa. They are large, with short antennae, and with the pronotum prolonged backward and hood-like. Unhappily, although amongst the most remarkable of insects, we are unacquainted with their beautiful specieshabits. We give an illustration of the Pnezivtora scutellai^is {sQ^ ¥\g. 22). While the male is bountifully winged, the female must be necessarily sedentary, because of the imperfection of her alar system. From the form of the hind legs and their short length, it may be presumed that their leaping powers are null, or but slight. P. snitellaris is very remarkable from the difterence in colour of the sexes. So brilliant is the female, she has been said to look as if "got up" for a fancy dress ball. She is of a bright green, with numerous marks or patches of pearly white, each of them invested with a disk of a mauve or magenta colour. Though the female is thus resplendent, her consort is of a modest, almost unornamented green. fie is, however, furnished with a musical apparatus, by which he may be enabled to charm his gorgeous but dumb spouse. It consists of a series of fine ridges situated on the sides of the inflated abdomen, this part of the body having every appearance of being inflated and tense with the result of increasing the volume and quality of the sound. The Pamphagides also chiefly inhabit Africa and the
arid regions on the shores of the Mediterranean Sea. Many are apterous forms, a circumstance that has, according- to Saussure, exercised a marked influence on the geographical distribution of the species; but several species have well-developed wings. Some of the species are modified to a great extent for a desert life, and exhibit a great variety in the tint of the individuals in conformity with that of the soil on which they live.
Colour Difference Correlative with Locality.
To the tribe Oedipodides we have already referred as including most of the species of migratory locusts of the Old World. Some remarkable cases of colour-variation have been noted amongst the winged Oedipodides. In some species the hind wings may be either blue or red; it is thought that the latter is the tint natural in the species, and that the blue-coloured wings are a kind of albinism. But the most remarkable thing is that this wing-colour is correlative with locality. In the few localities in Europe where the blue variety of Oe. variabilis occurs, for example, not a single red specimen can be met with. Attention has been drawn to similar phenomena in other species in North America, and L. Brunner suggests that the phenomena in that country are related to climatic conditions.
He finds red-winged species most common in humid regions, yellow-winged in more or less arid districts, while the blue-winged forms are found chiefly in mountainous regions just between the dry and the wet conditions; and this same variation is observed among the representatives of the tribe in Mexico. So characteristic does this variation in colour of the wings appear, that he almost comes to the conclusion that an examination of a fair representative collection of these insects would be a sufficient index of the climate of the region from which they came.
Modifications for a Desert Life.
The Eremobiens, a subdivision of Oedipodides, include some of the most interesting forms of Acridiidce. The most peculiar members of the group are some very large insects, specially modified for a sedentary and desert life. Metkone anderssoni, found in the Karoo Desert of South Africa, and one of the largest of the Acridiidce, is most noteworthy (see Fig. 23). This species is remarkable for its complex instruments for producing sound, and for the modification of its great hind legs, which have no saltatorial function, and but little, if any, power of locomotion, but act as parts of the sound-producing apparatus, and as agents for
protecting the sides of the body. Both sexes are possessed of sound-producing organs, though the female is deficiently provided as compared with the male. On examinincj the first abdominal segment in either sex, a peculiar swelling is seen bearing two or three strongly raised chltinous folds, which being struck by some peg-like projections on the inner side of the base of the femur, a considerable noise is produced. Immediately behind the folds, there is a prominent striated surface; this is rubbed by some fine asperities on the inner part of the femur. These structures appear to be phonetic, at least in the male; in the female they appear to be somewhat less well developed than in the other sex. The male has still another phonetic structure. His tegmina, though rudimentary, are much longer than in the female, and their prolonged part is strongly ridged, over which moves the edge of the denticulate and serrate femur, giving rise to a louder and different sound. In the female there is nothing analogous to this; and there can be little doubt it is a sound-producing instrument peculiar to the male. In situation it approaches the musical apparatus of the males of the Stenobothri and other Acridiidae. Methone anderssoni possesses large tympanal organs, which the small tegmina cover up. In no other member of the Eremobiens, in no other Orthopteron, are the phonetic organs so complex as