36 



where much of it will be eaten b}^ them. Under these circumstances 

 dependence has to be made upon the natural enemies, of which 

 there are many. Of course it will be readil^^ understood, that 

 any method given above for the destruction of leaf -rollers, will 

 also result in the destruction of whatever parasites may l)e infest- 

 ing them at the time. 



NATURAL ENEMIES. 



Omiodes caterpillars are attacked by a large number of species 

 of parasites, some of which are native, and several which are the 

 most valuable have been introduced. The most of the species are 

 kept in check by their natural enemies, so that they do not be- 

 come very numerous; in fact, several of them are very rare. 

 Two species feed so numerously on cultivated plants tliat they 

 l)ecome serious pests: accepia on sugarcane, and l>/ackdur?ii on 

 palms. These two species are preyed upon very extensively l)y 

 the parasites and checked considerably, Imt not sufficiently to 

 keep them from doing considerable injury in certain localities and 

 at certain seasons. Apparently the moths are more prolific in 

 the winter months (about December to March), and the parasites 

 are scarcer owing to their having had fewer caterpillars for them 

 to keep breeding on during the preceding summer. Hence, when 

 tlie winter broods of caterpillars appear, there may be two or 

 three generations of them before the parasites breed up to suffi- 

 (;ient numbers so that they produce any noticeable check on the 

 number of the caterpillars; then in another generation or two 

 the caterpillars may be much reduced in numbers and a large 

 percentage of them found to be parasitized; for example: on one 

 occasion 75% of the cane leaf-rollers in a field at Hutchinson 

 plantation, Hawaii, were found to be destroyed b}- one species of 

 parasite; at Olaa plantation, Hawaii, in a certain field, on one 

 occasion a much higher percentage of them than that were killed; 

 in Honolulu, of a large number of the palm leaf-roller caterpillars 

 collected, 90% were parasitized. 



Since there are so many species of parasites preying on the leaf- 

 rollers which are pests, it might be asked " Whj' do they not 

 lx>come exterminated, or at least cease to be pests?" Apparently, 

 with all of the parasites, they are still not jiumerous enough to 



