20 



It is evident that P. saccharicida may attack and live upon plants 

 other than sugar-cane. During the present investigations eggs have 

 been found in seven different kinds of grasses and three species of sedge- 

 like plants in Hawaii. These plants have been submitted for deter- 

 mination. Some of the grasses in question are very common, probably 

 over most of the lowland portions of the Islands. Many of the eggs 

 in these grasses were found to be parasitised by Paranagrus optabilis 

 and a few by Ootetrasticlius formosanus. Examinations of the grasses 

 in many localities have been made and the numbers of hoppers and 

 parasites bred from them are recorded. The presence of parasites in the 

 grasses explains how these can survive in the vicinity of harvested 

 fields where no cane may be present for some time and where no hopper 

 c^'gs or parasites would exist without the grass. Only those fields 

 adjoining cane- fields, or in their immediate vicinity, have as yet been 

 examined ; it remains to determine the extent to which the eggs occur 

 in the various grasses at gradually increasing distances from canefields. 

 It is expected that as the distance is lengthened between the grasses and 

 the cane-fields a rapid decrease will be found in the number of hoppers 

 present, and a zone will soon be reached where no hoppers occur. 



An important enemy of leaf-hopper parasites has been discovered, 

 namely, a large black earwig, Chelisoches morio, very abundant in the 

 cane -fields of the rainy belt in Hawaii. This earwig feeds readily on 

 adults of P. optabilis and the indications are that it prefers this food 

 to the leaf -hopper, although it certainly devours the latter to some 

 extent and has always been regarded as beneficial. Another enemy 

 of P. optabilis is a green Chrysopid. This has not been observed to any 

 extent, but one larva of the fly was seen within five minutes to capture 

 and suck the body fluids of four adults of P. optabilis. If these enemies 

 of the parasite are proved to be of serious importance, the burning of 

 trash should help to rid the fields of the earwig. Excessive rainfall is 

 also very detrimental to the parasites of the leaf-hopper,destroying very 

 many adults of P. optabilis and preventing their oviposition, while the 

 leaf- hopper shows a decided ability to seek protection under the leaves 

 and is far better able to resist heavy rain. 



The question of contamination of young sugar-cane by hoppers from 

 older, adjoining cane is discussed. The isolation of fields and the prac- 

 tice of harvesting all the cane at one time seems decidedly advantageous. 

 A typical flight or migration of P. saccharicida is described. The adults 

 fly low and slowly and alight upon cane or grasses near by. This 

 migration shows that a centre of dispersion, such as a half-grown field 

 of heavily infested cane, may provide all adjacent territory with leaf- 

 hoppers. The hoppers fly on fine, still evenings and no particular 

 direction is taken. Since they are nearly always flying at dusk in one 

 locality or another, it is considered that such predators as bats and 

 swallows would be of great benefit if introduced. Poorly cultivated 

 fields are frequently less infested with leaf-hoppers than well-cared-for 

 plantations ; this is probably because the cane has not grown so rapidly 

 and the leaves are not so tender, and also because Xiphidiimi varipenne, 

 the green grasshopper that oviposits on various grasses and feeds on 

 hoppers, becomes much more numerous where the grass is not so con- 

 sistently kept down. The subject of preference for various types of 

 cane shown by P. saccharicida will be further investigated. As the 



