Fig. 150—Eupsalis minuta. North America. A, Larva; B, pupa; C, female imago; D, head of male. (After Riley.)
In the higher forms of Brenthidae the rostrum of the female is perfectly cylindrical and polished, and the mandibles are minute, hard, pointed processes placed at its tip. This organ is admirably adapted to its purpose; it being used for boring a hole in wood or bark, in which an egg is subsequently deposited. The males in these cases are extremely different, so that considerable curiosity is felt as to why this should be so. In some cases their head is thick, and there may be no rostrum, while large powerful mandibles are present.
In other cases the rostrum is slender, but of enormous length, so that it may surpass in this respect the rest of the body, although this itself is so drawn out as to be quite exceptional in the Insect world:[[156]] the antennae are inserted near the tip of the rostrum instead of near its base, as they are in the female. The size of the males is in these cases usually much larger than that of the female.[[157]] The males of some species fight; they do not, however, wound their opponent, but merely frighten him away. In Eupsalis it appears that the rostrum of the female is apt to become fixed in the wood during her boring operations; and the male then extricates her by pressing his heavy prosternum against the tip of her abdomen; the stout forelegs of the female serve as a fulcrum and her long body as a lever, so that the effort of the male, exerted at one extremity of the body of the female, produces the required result at the other end of her body. The New Zealand Brenthid, Lasiorhynchus barbicornis, exhibits sexual disparity in an extreme degree: the length of the male is usually nearly twice that of the female, and his rostrum is enormous. It is at present impossible to assign any reason for this; observations made at the request of the writer by Mr. Helms some years ago, elicited the information that the female is indefatigable in her boring efforts, and that the huge male stands near by as a witness, apparently of the most apathetic kind.
Coleoptera of uncertain position.
There are three small groups that it is impossible at present to place in any of the great series of beetles.
Fam. 84. Aglycyderidae.—Tarsi three-jointed, the second joint lobed; head not prolonged to form a beak. The two most important features of Rhynchophora are absent in these Insects, while the other structural characters are very imperfectly known, many parts of the external skeleton being so completely fused that the details of structure are difficult of appreciation. Westwood considered the tarsi to be really four-jointed, but it is not at all clear that the minute knot he considered the third joint is more than the articulation of the elongate terminal joint. The family consists only of two or three species of Aglycyderes, one of which occurs in the Canary Islands, and one or two in New Zealand and New Caledonia. The former is believed to live in the stems of Euphorbia canariensis; a New Zealand species has been found in connection with the tree-ferna. Cyathea dealbata
Fig. 151—Aglycyderes setifer. Canary Islands. A, Imago; B, tarsus according to Westwood; C, according to nature; D, maxilla; E, labium.
Fam. 85. Proterhinidae.—Tarsi three-jointed, the second joint lobed; head of the male scarcely prolonged, but that of the female forming a definite rostrum; maxillae and ligula entirely covered by the mentum. As in the preceding family the sutures on the under side of the head and prosternum cannot be detected. The minute palpi are entirely enclosed in the buccal cavity. There is a very minute true third joint of the tarsus, at the base of the terminal joint, concealed between the lobes of the second joint. The family consists of the genus Proterhinus; it is confined to the Hawaiian Islands, where these Insects live on dead wood in the native forests. The genus is numerous in species and individuals.