The testes in earwigs are peculiar and simple; they consist, on each side, of a pair of curvate tubular bodies, connected at their bases and prolonged outwards in the form of an elongate, slender vas deferens. The structures in the males of several species have been described at some length by Meinert,[[137]] who finds that in some species a double ejaculatory duct exists.
Fig. 111.—Ovaries of Labidura riparia, A; and Forficula auricularia, B. (After Dufour.)
The young is similar to the adult in form; in the winged forms it is always easy to distinguish the adult by the full development of the wings, but in the wingless forms it can only be decided with certainty that a specimen is not adult by the softer and weaker condition of the integuments. Scarcely anything appears to be known as to the life-history, except a few observations that have been made on the common earwig; Camerano found[[138]] that this Insect has certainly three ecdyses, and possibly an earlier one which he failed to notice, and his observation confirms the vague previous statement of Fischer. The eggs, in the neighbourhood of Turin, are deposited and hatched in the early spring; in one case they were laid on the 10th March, and the Insects issuing from them had completed their growth and were transformed into perfect Insects on the 22nd May. In the immature state the alar structures of the future imago may be detected. The tegmina-bearing sclerites, t, Fig. 112, look then somewhat like those of some of the apterous forms (Fig. 106) and, as shown in A and B, Fig. 112, do not differ greatly in the earlier and later stages. The wings, however, change much more than the tegmina do; at first (Fig. 112, A) there is but little difference between the two, though in the interior of the wing-flap some traces of a radiate arrangement can be seen, as shown at W in A, Fig. 112; in a subsequent condition the wing-pads are increased in size and are more divided, the appearance indicating that the wings themselves are present and packed about a centre, as shown in W of B, Fig. 112.
Fig. 112.—Notal plates from which the tegmina and wings of Forficula auricularia are developed in young, A, and more advanced, B, nymph.
In the young of the common earwig the number of joints[[139]] in the antennae increases with age. Camerano, l.c., says that before emergence from the egg there are apparently only 8 joints in the antennae, and Fischer states that the larvae of F. auricularia have at first only 8 antennal joints; later on 12 joints are commonly found, and, according to Bateson,[[140]] this number occasionally persists even in the adult individual. Meinert says[[141]] that the newly hatched Forficula has either 6 or 8 joints, and he adds that in the later portion of the preparatory stage the number is 12. Considerable discrepancy prevails in books as to the normal number of joints in the antennae of the adult F. auricularia, the statements varying from 13 to 15. The latter number may be set aside as erroneous, although it is, curiously enough, the one given in the standard works of Fischer, Brunner, and Finot. Meinert gives without hesitation 14 as the number; Bateson, l.c., found that 14 joints occurred in 70 or 80 per cent of adult individuals, that 13 was not uncommon, that 12 or 11 occasionally occurred, and that the number may differ in the two antennae of the same individual. These variations, which seem at first sight very remarkable, may with probability be considered as due to the fact that in the young state the number of joints increases with age, and that the organs are so fragile that one or more of the joints is very frequently then lost, the loss being more or less completely repaired during the subsequent development. Thus a disturbing agency exists, so that the normal number of 14 joints is often departed from, though it appears to be really natural for this species. Bateson has also pointed out that when the normal number of articulations is not present, the relative proportions of joints 3 and 4 are much disturbed. It is, however, probable that the increase in number of the joints takes place by division of the third or third and fourth joints following previous growth thereof, as in Termitidae; so that the variations, as was suggested by Bateson, may be due to mutilation of the antennae, and consequent incompletion of the normal form of the parts from which the renovation takes place; growth preceding segmentation—in some cases the growth may be like that of the adult, while the segmentation remains more incomplete. In the young the forceps of the two sexes differ but slightly; the form of the abdominal rings is, on the contrary, according to Fischer, already different in the two sexes in the early stage.
The common earwig has a very bad reputation with gardeners, who consider it to be an injurious Insect, but it is probable that the little creature is sometimes made the scapegoat for damage done by other animals; it appears to be fond of sweets, for it often makes its way to the interior of fruits, and it no doubt nibbles the petals, or other delicate parts of flowers and vegetables. Camerano, however, states, l.c., that the specimens he kept in confinement preferred dead Insects rather than the fruits he offered them. Rühl considers the earwig to be fond of a carnivorous diet, eating larvae, small snails, etc., and only attacking flowers when these fail.[[142]] It has a great propensity for concealing itself in places where there is only a small crevice for entry, and it is possible that its presence in fruits is due to this, rather than to any special fondness for the sweets. This habit of concealing itself in chinks and crannies in obscure places makes it an easy matter to trap the Insect by placing pieces of hollow stalks in the situations it affects; inverted flower-pots with a little hay, straw, or paper at the top are also effectual traps. We have remarked that it is very rarely seen on the wing, and though it has been supposed to fly more freely at night there is very little evidence of the fact. Another British species, Labia minor, a smaller Insect, is, however, very commonly seen flying.
Earwigs have the reputation of being fond of their young, and Camerano describes the female of the common earwig as carefully collecting its eggs when scattered, lifting them with its mandibles and placing them in a heap over which it afterwards brooded. De Geer[[143]] more than a century ago observed a fondness of the mother for the young. After the eggs were hatched, Camerano's individual, however, evinced no interest in the young. A larger species, Labidura riparia (Fig. 110) is said to move its eggs from place to place, so as to keep them in situations favourable for their development.
The name "earwig" is said to be due to an idea that these creatures are fond of penetrating into the ears of persons when asleep. Hence these Insects were formerly much dreaded, owing to a fear that they might penetrate even to the brain. There does not appear to be on record any occurrence that could justify such a dread, or the belief that they enter the ears. If they do not do so, it is certainly a curious fact that a superstition of the kind we have mentioned occurs in almost every country where the common earwig is abundant; for it has, in most parts of Europe, a popular name indicating the prevalence of some such idea. It is known as Ohren-wurm in German, as perce-oreille in French, and so on. The expanded wing of the earwig is in shape so very like the human ear, that one is tempted to suppose this resemblance may in former ages have given rise to the notion that the earwig has some connexion with the human ear; but this explanation is rendered very improbable by the fact that the earwig is scarcely ever seen with its wings expanded, and that it is a most difficult matter to unfold them artificially, so that it is very unlikely that the shape of the wings should have been observed by untutored peoples.