Page:Encyclopædia Britannica, Ninth Edition, v. 16.djvu/360

Rh 342 bare black patch round the eyes; this is copied in the Mimeta by a patch of black feathers. The top of the head of the Tropidorhynchus has a scaly appearance from the narrow scale-formed feathers, which are imitated by the broader feathers of the Mimeta having a dusky line down each. The Tropidorhynchus has a pale ruff formed of curious recurved feathers on the nape (which has given the whole genus the name of friar-birds) ; this is represented in the Mimeta by a pale band in the same position. Lastly, the bill of the Tropidorhynchus is raised into a protuberant keel at the base, and the Mimeta has the same character, although it is not a common one in the genus. The result is that on a superficial examination the birds are identical, although they have important structural differences, and cannot be placed near each other in any natural arrangement.&quot; Allied species of Tropidorhynchus in Ceram and Timor are similarly mimicked by the local Mimeta of each island. Mr Osbert Salvin has likewise noticed a case of mimicry among the birds of prey near Rio Janeiro. An insect-eating hawk, Harpagus diodon, is closely resembled by a bird-eating hawk, Accipiter pileatus. Here the advantage seems to be that the small birds have learned not to fear the Harpagus, and the Accipiter is able to trade upon the resemblance by catching them unawares, both birds being reddish-brown when seen from beneath. But the Accipiter has the wider range of the two ; and where the insect-eating species is not found it no longer resembles it, but varies in the under wing-coverts to white. Here again the resemblance, though advantage ous, is not protective. Among reptiles, Mr Wallace has instanced some curious cases where a venomous tropical American genus of snakes, Elaps, with brightly-banded colours, is closely mimicked by several genera of harmless snakes, having no affinity with it, but inhabiting the same region. Thus the poison ous Elaps fulvus of Guatemala has black bands on a coral- red ground ; the harmless Pliocerus sequalis of the same district is coloured and banded precisely like it. The likeness affords the unarmed snakes a great protection, because other animals probably will not touch them, mis taking them for the venomous kinds. It is among the invertebrates, however, and especially among insects, that cases of mimicry are most frequent and were first observed. In the order Lepidoptera, besides the classical instance of Leptalis and the Heliconidiz, a genus of another family, the Erycinidse, also mimics the same group. The flocks of one species of Ithomia, an uneatable butterfly, often have flying with them a few individuals of three other widely different genera, quite indistinguishable from them when on the wing. In the tropics of the Old World, the Danaidse and A crxidx possess a similar protec tive odour, and are equally abundant in individuals ; they are closely mimicked by various species of Papilio and Diadema. Mr Trimen, in a paper on &quot; Mimetic Analogies among African Butterflies,&quot; gives a list of sixteen species or varieties of Diadema or its allies, and ten species of Papilio, each of which mimics a Danais or Acrxa of the same region in the minutest particulars of form and colour. The Danais tytia of India has semi-transparent bluish wings, and a border of reddish-brown ; this coloration is exactly reproduced in Papilio agestor and Diadema nama, all three insects frequently coming together in collections from Darjiling. In the Malay Archipelago the common and beautiful Euplxa midamus is so exactly mimicked by two rare species of Papilio that Mr Wallace generally mistook the latter at first for the ordinary insect. An immense number of other instances among the Lepidoptera have been quoted from other parts of the world. Occasionally species of Lepidoptera also imitate insects of other orders. Many of them take on the appearance of bees or wasps, which are of course protected by their stings. Thus the Sesiidse and ^Egeriidx, two families of diurnal moths, have species so like hymenoptcrous insects that they are known by such names as apiformis, vespiforme, ichneumoniforme, sphegiforme, and so forth. The British sesia bombiliformis closely resembles the humble bee ; the Sphecia craboniformis is coloured like a hornet, and carries its wings in the same fashion. Some Indian Lepidoptera have the hind legs broad and densely hairy, so as exactly to imitate the brush-legged bees of the same country. Mr Belt mentions a Nicaraguan moth, Pionia lycoides, which closely mimics a distasteful coleopterous genus, Calopteron ; and Professor Westwood pointed out that the resemblance to the beetle is still further increased in the moth by raised lines of scales running lengthwise down the thorax. Among the Coleoptera, or beetles, and other orders, similar disguises are not uncommon. Mr Belt noticed species of Hemiptera and Coleoptera, as well as spiders, in Nicaragua, which exactly resemble stinging ants, and thus no doubt escape the attacks of birds. The genus Calopteron is mimicked by other beetles, as well as by the moth Pionia. In the same country, one of the Hemiptera, Spiniger luteicornis, has every part coloured like the hornet, Priocnemis, which it mimics ; &quot; in its vibrating coloured wing-cases it departs greatly from the normal character of the Hemiptera, and assumes that of the hornets.&quot; Mi- Wallace mentions the longicorn beetle, Cyclopeplus bate.ni , which &quot; differs totally in outward appearance from every one of its allies, having taken upon itself the exact shape and colouring of a globular Corynomahis, a little stinking beetle, with clubbed antennas.&quot; Erythroplatis corallifer, another longicorn, almost exactly resembles Cephalodonta spinipes, one of the common South-American Hispidx, which possesses a disagreeable secretion ; and Mr Bates also found a totally different longicorn, Streptolabis hispoides, which resembles the same insect with equal minuteness. Some of the large tropical weevils have the elytra so hard that they cannot be pierced by a bird s beak ; and these are mimicked by many other comparatively soft and eatable insects. In southern Brazil, Acanthotritus dorsalis closely resembles a Curculio of the hard genus Heiliplus ; and Mr Bates found Gymnocerus cratosomoidcx, a longicorn, on the same tree with the hard weevil, Cratosomus, which it mimics. Other beetles resemble bees, wasps, and shielded bugs. Hairy caterpillars are well known to be distasteful to birds, and comparatively free from attack ; and Mr Belt found a longicorn, Desmipkora fasciculata, covered with long brown and black hairs, and exactly mimicking some of the short, thick, woolly caterpillars common on the bushes around. Amongst other orders, one of the most interesting cases is that of certain Diptera or two-winged flies which mimic wasps and bees. Sometimes this likeness only serves to protect the insect from attack, by inspiring fear of a sting. But there are also a number of parasitic flies whose lame feed upon the larvae of bees, as in the British genus Volucella ; and these exactly mimic the bees, so that they can enter the nests or hives to deposit their eggs without being detected even by the bees themselves. In every country where such flies occur they resemble the native bees of the district. Similarly, Mr Bates found a species of Mantis on the Amazons which exactly mimicked the white ants on which it fed. On the other hand, the defenceless species itself may mimic its persecutor, as in the case of several crickets, Scaphura, that exactly resemble various sand-wasps, and so escape the depredations of those cricket-killing enemies. Another cricket from the Philippine Islands, Condylodera tricondyloides, so closely copies a tiger-beetle, Tricondyla, that even Professor Westwood long retained it among that group in his cabinet,