228 A NATURALIST IN BORNEO 



numbers of parasitic Hymenoptera of the family 

 Braconidce. Some of these, mostly of the genus 

 Myosoma, are black with reddish head and thorax, 

 and they are mimicked by Longicorns of the genus 

 Oberea. The Eraconidce fly about very freely, they 

 are wasp-waisted like so many Hymenoptera, and 

 when they settle on a leaf they have the habit of 

 walking about waving the antennae up and down in 

 a very characteristic manner ; the black wings are 

 folded down over the back so that seen from above 

 the wasp-waist is not visible. Now three species of 

 Oberea resemble the Braconids in a very remarkable 

 way ; the colouring is the same, and a wasp-waisted 

 effect is produced by a patch of silvery white pubes- 

 cence on each side of the first and second abdominal 

 segments ; the part of the body covered with this 

 pubescence tends to disappear from sight altogether, 

 and the beetle looks as if the rest of the abdomen 

 was slung on to the thorax by a mere pedicel as is 

 really the case in the Braconidce. It may be added 

 that all the Obereas are active fliers, all have the 

 habit of agitating the antennae when walking about, 

 and some of the species are so slender, and have the 

 wing-cases so narrowed, that they look even more like 

 Hymenoptera than the species with false wasp-waists. 



This kind of colouring whereby certain parts of the 

 body, or even the whole body, may be made to dis- 

 appear from sight is very common in the animal 

 kingdom, but it actually occurs that an organ can be 

 so constructed that part of it is practically invisible 

 even when exposed. The little Longicorns of the genus 

 Xyaste mimic beetles of the family Lycidce ; now the 

 Lycidce have short thick, flattened antennae, but the 



