246 MR. K. SHELFORD OIS' MIMETIC INSECTS AND [NoV. 4, 



figs. 4, 5, 6). The Brentliicls 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 antennse. The three species here noted range in 

 length from "75 in. to 1*5 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 le?s closely circum- 

 scribed area, and all belonging to the same subfamily. 



In the fi^rst couple Diurus sylvanus (Senna) (a female) measures 

 1'5 in. in length, and the mimic Mgopreiois 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 Longicorn do not terminate in sharp points correspond- 

 ing 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 antennse are shorter and 

 thicker ; and similarly we find that the antennas of the mimic, 

 which, when carried in the natural attitude {i. e., pointing 

 forward and closely apposed), simulate the rostrum and antennse 

 of the Brenthid, are plumose for a greater part of their length 

 than in Alihora sp., whilst the free portion is short and thick, 

 not long and setaceous as in the Alihora. Both model and mimic 

 were taken on a fallen log close together. 



Ectatosia vioorei (Pasc.) is a mimic of D. shelfordi (Senna) ( $ ), 

 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 yEgoprepis 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 po7-osus (Pasc.) 

 (Plate XX. fig. 9), mimics — again by the same means — a small 

 JJiurus forcipatus (Westw.) measuring only '75 inch in total length 



