cxviii FAUNA HAWAIIENSIS 



fact that the females of Plagithmysus readily attract the males, not one example of 

 either of these has ever been found to attack the tree affected by the others, varians 

 being restricted to Acacia koa, lamarckianns to Pipturus, and darwmianus to Sophora 

 chrysophylla. It is pretty certain that, however slight be the characters that separate 

 these species, no interbreeding takes place between them, each remaining constant 

 to its own food-plant. In fact, almost all the known species of the genus remain 

 equally attached to their special food-plant, and as it might be supposed that change 

 from one food to another may have in some of these cases led to the formation of 

 species, we must refer to the case of P. vitticollis and its van longulus. 



The van longtilus is one of the most constant in a general way of the species of 

 the genus and its larva lives beneath the bark of Bodea, a Rubiaceous forest tree. 

 P. vitticollis (typical) affects a native species of Rubus (Rosaceae). Some of the 

 examples (perhaps most) exhibit pallid colouring on the elytra, which is never the 

 case with the var. longulus. Where the latter form occurs we have not found 

 individuals attacking Rubus, though it grows there. The true vitticollis, found on 

 Rtibus, were a few miles from the locality, where the van longulus occurred, and 

 perhaps no Bobea grew there. 



The case of P. bishopi is also remarkable. This is attached to Pelea, a 

 Rutaceous tree. On one occasion near by some Pelea trees, affected by bishopi, 

 I found a different tree, Zanthoxylon sp., on which were specimens of this Plagith- 

 mysus. This particular tree had been known to me for years, when it was in sound 

 condition, but had now been injured and attracted the beetles. There were many 

 larvae feeding in the bark and the larger ones were taken and subsequently bred, 

 yielding perfectly typical examples of P. bishopi. It may be noted that a curious 

 variety (var. gracilis) of P. bishopi was previously found in the same locality on an 

 unidentified tree other than Pelea, and I have some suspicion that this tree may have 

 been of the same species as the one above mentioned. Although the individuals that 

 were bred proved to exhibit no variation, yet it would have been very interesting to 

 have continued this breeding, as in course of time it is by no means unlikely that 

 variation would have shown itself It remains to notice the case of P. sulphurescens 

 and giffardi. The first specimens of sulphurescens were taken on the Urticaceous 

 tree, Urera sandtvichensis, and are described as having the base of the elytra fulvous. 

 Some, captured on the wing I believe, had this part black. P. giffardi shows no 

 variation and has the elytra black at the base. It is attached to My r sine (Myrsinaceae), 

 and this may have been the case with examples, taken flying, in my early collections. 

 It is therefore uncertain whether the two are really distinct. 



Whereas most of the species of Plagithmysus attack only unhealthy trees or such 

 parts as are in unsound condition, some affect those that are apparently quite healthy. 

 Thus P. perkinsi, as evidenced by the exit holes of the beetles, sometimes breeds 

 numerously in trees of Myoporum, without noticeably injuring the tree,, and the larvae 



