other birds that were given to it. It is clearly possible, therefore,
that cuckoos which mimic drongos and hawks may be protected from
those enemies which find these birds distasteful.
One of the most perfect cases of mimicry in birds is presented by a Madagascar thrush or babbler (Tylas eduardi), which resembles feather for feather a shrike (Xenopirostris polleni), from the same island. The Tylas has departed from the normal coloration of its group to take on that of the shrike, a comparatively powerful and pugnacious bird. Analogous cases are supplied by the mimicry that exists between some of the orioles (Mimeta) and the friar-birds (Philemon or Tropidorhynchus) of the Austro-Malayan Islands. The friar-birds are noisy and pugnacious species of the group of honey-eaters, and mob hawks and other birds of prey, which leave them unmolested. The general style of coloration of orioles is gaudy yellow and black, rendering them invisible in sunlit foliage, and quite different from the more sombre hues of the friar-birds; but in the islands of Bourou, Timor and Ceram the orioles have not only assumed the tints of friar-birds in general, but in each of the islands named a species of oriole has acquired the little peculiarities in colour of plumage possessed by the friar-bird of the same locality. There seem to be no reasons for doubting that these are cases of genuine protective mimicry.
Apparently the only instances of mimicry known amongst reptiles occur amongst snakes; and in all the cases quoted by Wallace harmless snakes mimic venomous species. In tropical America the genus Elaps, which is both poisonous and warningly coloured, is a model for several innocuous snakes. In Guatemala Elaps fulvus is mimicked by Pliocerus equalis; in Mexico Elaps corallinus by Homalocranium semicinctum, and in Brazil, Elaps lemniscatus by Oxyrhopus trigeminus. In South Africa the harmless egg-eating snake (Dasypeltis scaber) is very like the Cape adder (Bitis atropos); and in Ceylon the harmless Colubrine Lycodon aulicus is alleged to mimic Bungarus ceylonicus, an ally of the deadly krait of India. Considering, however, the numbers of venomous and innocuous snakes that occur in most tropical countries, it might be supposed that mimicry in this order of reptiles would be of commoner occurrence than appears to be the case. It must be remembered, however, that apart from size and colour all snakes resemble each other in a general way in their form and actions. They present a strong family likeness which is not found in any other terrestrial vertebrated animals with exception of some lizards and possibly Caecilians amongst the Amphibia. So close indeed is the similarity that many monkeys, apes and human beings have an apparently instinctive fear of all snakes and do not discriminate between poisonous and non-poisonous forms. Hence it may be that innocuous snakes are in many instances sufficiently protected by their likeness in shape to poisonous species that close and exact resemblance in colour to particular species is superfluous.
As a possible instance of mimicry in fishes, A. T. Masterman recalls the fact that two species of weever (Trachinus draco and T. vipera), have the same habitat in British waters as certain species of soles (e.g. Solea vulgaris). The weevers are poisonous and the venom is concentrated principally in the six spines of the first dorsal fin. These spines are sharp and connected by a black membrane which projects, when the fish is disturbed, as a danger signal, it is believed, above the surface of the sand in which the fishes lie hid awaiting prey. For protective purposes soles, which are edible, also lie buried in or on the sand which they match in colour, with the exception of the right or upper pectoral fin which has a large black patch. When disturbed the soles raise this black fin and, as a rule, hold it rigid so that it becomes a very conspicuous object. If the view that the sole is protected by the blackness of the pectoral fin resembling the blackness of the dorsal fin of the weever, be correct, these fishes furnish an instance of Batesian mimicry. Furthermore, there is a common littoral fish in the Mediterranean (Uranoscopus scaber), belonging to the same family as Trachinus, exhibiting the same habits and living on the same ground, which also has a jet black erectile dorsal fin, and is believed to be poisonous. It is probable that the resemblance between Uranoscopus and Trachinus with respect to the colour of the dorsal fin is mutually beneficial to the two fishes. If so, the likeness must be regarded as an instance of Müllerian mimicry.
It is amongst Arthropods, however—and especially amongst insects—that mimicry, both Batesian and Müllerian, occurs in greatest profusion and perfection.
In insects of the order Orthoptera, departure from the normal in form and colour, carrying with it similarity to other living things, usually takes the line of protective resemblance to parts of plants. This is well exemplified by the leaf-insects (Phyllium) and stick-insects (Bactra), where the likeness to the models after which they are named is procryptic; and also by various species of tropical Mantidae which resemble flowers for the purpose of alluring insects within striking distance and perhaps also for concealing their identity from enemies. Some cases of genuine mimicry, however, are known in the order; Perhaps the best is that of the Sudanese Locustid (Myrmecophana fallax), which is strikingly ant-like. The head is large, the neck slender, the antennae short and the legs longish, and the appearance of the long stalk-like waist of the ant is produced by a patch of whitish hair on each side of the forepart of the abdomen which has the effect of cutting away the parts of the segments so covered, leaving a narrow dark-coloured median area to represent the waist. This at least is the method of disguise suggested by examination of the dried insect; but representatives of the same or an allied species found in Mashonaland were observed in the living state to be green with the antlike parts represented in black pigment. These parts were quite conspicuous against the green of the plants frequented by the insects, wherever the green portions were rendered invisible by the same background. Ant-mimicry has also been recorded in the case of the larva of one of the Indian species of Mantidae. Again, several species of this order have become profoundly modified in form in imitation of inedible beetles. In the Philippines, a cricket (Scepastus pachyrhynchoides), has taken on the shape and coloration of a species of Apocyrtus, a hard and inedible weevil (Curculionidae); and Phoraspis, a kind of grasshopper similarly resembles ladybirds (Coccinellidae). A species of beetle (Caria dilatata) of this family in Borneo is mimicked by a species of a genus allied to Gammarotettix not only in shape and coloration but also in the habit of remaining still when disturbed. In the same island a species of Gryllacris mimics Pheropsophus aquatus, a “Bombardier” beetle which ejects a puff of volatile formic acid when attacked; and Condylodera tricondyloides mimics different species of tiger-beetles (Cicindelidae) at different stages of its growth. Finally the larva of one of the Bornean Mantidae, which is a floral simulator in its pupal and adult stages, closely resembles in its black and red coloration the larva of the stinking and warningly coloured bug Eulyes amoena.
Comparatively few cases of mimicry in the Neuroptera have been observed. There are records, however, of species of Mantispa mimicking the wasp Polistes in North America and Borneo and Belonogaster in South Africa; and other species of the genus imitate parasitic hymenoptera of the genera Bracon and Mesostenus.
Coleoptera (beetles) supply instances of mimicry of ants, wasps and Ichneumonids, and some defenceless forms of this order mimic others that are protected. A good illustration of wasp-mimicry is furnished by a large heteromerous beetle (Coloborhombus fasciatipennis) from Borneo which is remarkably like a large wasp (Mygnimia aviculus) from the same island. The front wings of the wasp have a conspicuous white patch near the tip and a patch similar in size and colour is present on the wings of the beetle, which, unlike the majority of beetles, habitually keeps its wings extended, and since the elytra are exceptionally short the wings are not covered by them when folded. The resemblance also extends to the general form of the body and to the length and thickness of the wings and antennae. The elytra are equally reduced, and apparently for the same purpose, in an Australian Longicorn beetle (Esthesis ferrugineus), which, like so many wasp-like Hymenoptera, has the body banded red and black. This beetle probably mimics the Australian hornet (Abispa australis). In the European Longicorn (Clytus arietis), on the other hand, the elytra are of normal length and are banded with yellow stripes. The beetle, moreover, is of slender build and all its actions are suggestively wasp-like. This may, however, be an instance of Müllerian rather than of Batesian mimicry, the beetle being itself inedible; for Shelford has stated his conviction that the Bornean representatives of the sub-family (Clytinae), to which Clytus arietis belongs, are all highly distasteful and are warningly coloured, as are members of this sub-family from other parts of the world.
In the Philippine Islands several species of Longicorns of the genus Doliops mimic hard inedible weevils (Curculionidae) of the genus Pachyrhynchus. The antennae of these weevils are short and end in a knob; those of the Longicorns are very much larger, but the weevil-like look is produced by the presence of a knob-like swelling upon the third joint, the terminal portion of the antenna being so extremely fine as to be almost invisible. Similar modification of the antennae in the Longicorn Estigmenida variabilis brings about the resemblance between this beetle and a beetle, Estigmena chinensis, one of the Phytophaga of the family Hispidae. Numerous instances of mimicry in this order of insects have recently been recorded from Borneo by R. W. C. Shelford, a large number of them being in all probability Müllerian.
Instances of ant-mimicry, unique in the method employed to bring about the resemblance, are supplied by some insects of the Homopterous group of the Rhynchota, belonging to the family Membracidae. In one of these (Heteronotus trinodosus), the dorsal area of the forepart of the thorax is developed into a plate which projects backwards over the body of the insect, which retains its normal form, and conceals all but the head, wings and legs. This shield if shaped in such a manner as to resemble closely the body of an ant, the median portion of the shield being deeply constricted in imitation of the waist and the terminal portion sub-globular like the abdomen of the ant. This insect comes from Central America. Still more curious is the mimicry of another of these insects from Venezuela which is found in company with a leaf-cutting ant (Oecodoma cephalotes) of that country. When pursuing their operations of leaf-storage, these ants present the appearance of a crawling crowd of leaf-particles, fragments of leaves being carried by the insects in such a way as to conceal to a great extent the insect underneath, of which little more than the dark coloured legs project beyond the burden. The immature form of the above-mentioned species of Membracidae mimics both ant
