INTRODUCTION cxix 



of P. speculifer live in the stems of Urera, which appear quite sound. Many of the 

 species can be obtained in any number by felling the kinds of trees that they affect, 

 in many cases the beetles appearing in numbers two or three days after a tree is 

 .cut down and continuing to be found for weeks. P. perkinsi, spectdifer, vitticollis 

 and others, when in the larval condition, often feed in the actual wood or in the pith 

 of the trees, but most of the species feed in or just beneath the bark, leaving long flat 

 grooves, where they have fed. Before pupation, however, these usually enter the 

 wood for that purpose. A few of the species are much more sluggish than the very 

 active majority, though even these (e.g. P. puherulenttis and perkinsi) can run with 

 speed on occasion. In dull weather the beetles are found with difficulty, in fact at 

 such times and at night they appear generally to leave the trees they affect. In the 

 very early morning we have several times seen individuals rise out of the underbrush 

 and fly to the tree trunks, as the sunshine became warmer, they having evidently 

 rested during the night amongst the lower-growing plants. 



Like the common introduced Clytns crinicornis, the males are very active in 

 pursuit of the females, and both sexes copulate with different individuals. Where 

 there is conspicuous di- or trimorphism the females will pair successively with males 

 of each form. The male often accompanies the female as she oviposits, holding on 

 with the front and walking with the hind legs, and every now and then copulating 

 afresh. 



Plagithniysus is attacked by the two Braconid parasites of the genus Ischiogonus, 

 one of which first appeared about 15 years ago, while the other (which also inhabits 

 Fiji) is a more ancient introduction. Several parasites may be bred from a single 

 partly grown larva. On one occasion, of over 80 larvae of P. solitarius taken on 

 the mountains just behind Honolulu only two small individuals had escaped these 

 parasites. 



The species of Callithmysus resemble those of Plagithnysus in habits, and the 

 two genera are intimately connected. The three species inhabit only Oahu, and one 

 of them, C. cristatus, was formerly considered to be a Plagithmysus. This species 

 seems closely connected with P. rolnistjis {pidvernlentiis), and the Maui species 

 P. fimebris is also somewhat similar to these. It would appear that all or most of 

 the known Oahuan Plagitlmtysus have a tendency towards the Callithmysus form, 

 the thickness of the hind legs being very noticeable as compared with those of allied 

 species from the other islands. C. cristatus is attached to Acacia koa and is often 

 found in company with P. pidverulentus, but C. koebelei is found on Pipttirus and 

 C. viicrogaster on Bobea, all of which trees are favourites of Plagithmysus. 



CuRCULiONiDAE. — The 24 described species of Rhyncogonus are endemic with the 

 possible exception of one or two, which may be natural immigrants. These R. vestitus 

 and R. extranetis live outside the forest region and are attached to apodemic plants. 



