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Show 2 46 MR. R. SHELFORD ON MIMETIC INSECTS AND [Nov. 4, figs. 4, 5, 6). The Brenthids are extremely variable in both sexes, in the matter of size, in the shape and length of the terminal processes of the elytra, and in the amount of scaling on the head and antennae. The three species here noted range in length from -75 in. to T5 in .; and it is of exceptional interest that three mimetic Longicorns of sizes corresponding closely to these forms should be found in a more or less closely circumscribed area, and all belonging to the same subfamily. In the first couple Diurus sylvanus (Senna) (a, female) measures T5 in. in length, and the mimic jEgoprepis insignis (Pasc.) is of corresponding length (compare figs. 4 & 7 on Plate XX.). Both species are dark brown, relieved with pale ochreous streaks and spots; the Brenthid has the prothorax and elytra densely and deeply punctured, the punctures on the elytra being arranged in close-set rows. Both on the prothorax and elytra each puncture is occupied by a peculiar scale, lenticular in shape and pale ochreous in colour; these produce the pale ochreous streaks characteristic of the beetle (fig. 4 a). The head and antennae are covered by similar scales, more closely set and not imbedded in punctures; each elytron terminates in a somewhat sharp point, the homologues of the long, narrow, terminal processes of the male. The mimic has the ground-colour of the prothorax and elytra black, and their dorsal surfaces are covered with tufts of a fine pale ochreous pubescence (fig. 7 a ) ; these represent very well the scales of the Brenthid, and a very similar mottled appearance is thus produced in both species by totally different means. The elytra of the Longicoi n do not terminate in sharp points corresponding to the points of the Brenthid's elytra, as in the two species mentioned below. The rostrum of the model is slightly longer than in Baryrhynchus dehiscens, but the antennae are shorter and thicker; and similarly we find that the antennae of the mimic, which, when carried in the natural attitude (i. e., pointing forward and closely apposed), simulate the rostrum and antennae of the Brenthid, are plumose for a greater part of their length than in Alibora sp., whilst the free portion is short and thick, not long and setaceous as in the Alibora. Both model and mimic were taken on a fallen log close together. Ecialosia moorei (Pasc.) is a mimic of J). shelfordi (Senna) ( 5 ), a species of medium size, 1 inch in length (compare fig. 10 with 6 and 10 a with 4 a on Plate XX.). The simulation is as perfectly carried out and by the same means as in JEgoprepis insignis, with this addition, that the elytra terminate in sharp points corresponding to the same points in the Brenthid. The length of the mimic from elytra tips to termination of the plumosity of the antennae is approximately the same as the length of the model from elytra tips to tip of the rostrum. Another and a smaller species, Dymascus porosus (Pasc.) (Plate XX. fig. 9), mimics-again by the same means-a small Diurus forcipatus (Westw.) measuring only -75 inch in total length |