100 



are native, but there are quite a number that have been pur- 

 posely introduced. There are also a few that, tho originally 

 described from here, are not to be considered as endemic, for 

 they are also now known elsewhere. There are a few also that 

 have made their appearance here the past few years thru the 

 channels of commerce, at least not purposely introduced. Some 

 of these have not yet been determined. 



Other factors are also active in keeping- the Lepidoptera in 

 check, but it is very certain that- the Hymenopterous parasites 

 play an important part, and are largely responsible for the 

 scarcity of many of the native species of moths in the mountains 

 of the Hawaiian Islands. As proof of their scarcity one has 

 but to spend a day collecting moths or caterpillars in the moun- 

 tains. 



Another indication of the scarcity of many species is found 

 in the Fauna Hawaiiensis. With all the thoro collecting by Dr. 

 Perkins, of the 310 species of Macrolepidoptera listed or de- 

 scribed in the Fauna, -14 species or 1-4% were described from 

 single specimens; and 36 species or 11% were described from 

 but two specimens. Of the -441 Microlepidoptera, 100 species 

 or 24% were described from a single specimen; and Tl species 

 or 16% from but two specimens. Taken as a whole, 20% of all 

 the species Avere described from single specimens, and 14% 

 from but two specimens. If the introduced species were sub- 

 tracted from the total number, and these percentages taken only 

 on the native species they would be still higher. 



Of course there are some species of moths that are known 

 to be common or abundant in the mountains, so much so that 

 sometimes their caterpillars are found defoliating the |")articu- 

 lar trees or shrubs on which they customarily feed. This may 

 be due to the fact that usually the relationship between insect 

 parasites" and their hosts is such that there is a variable ratio 

 in numbers between parasite and host, depending often on some 

 conditions which are more favorable or more detrimental to 

 one or to the other, the host or the parasite, sometimes the one 

 being most affected and sometimes the other. Oftentimes, as 

 with certain leaf-miners, from the appearance of the leaves on 

 the trees it would seem that the moth should be numerous ; but 

 when the mined leaves are collected to rear the moths it is found 

 that they had mostly been parasitized. 



There are yet many parasites whose hosts and habits are 



