194 



parasites,^ and some are notable for the peculiar adaptations 

 to their host during their larval life. The habile of species 

 throughout the whole family may in fact be considered highly 

 specialized in regard to their host relationships. Many species 

 indeed so far as we know seem to be confined exclusively to 

 one species of host and may be called monoxenotic in habit. 

 Others are known to attack and successfully parasitize two or 

 more species of hosts generally belonging to the same or closely 

 allied genera, and these parasites may he cited conveniently as 

 polyxenotic in habit. 



Among our immigrant species of Encyrtidae we know rath- 

 er definitely that Adelencyrtus odonaspidis, Anagyrus swezeyi, 

 Aphycomorpha araucariae, Blepyrus ■mexicanus, Pauridia pere- 

 grina, Pseudococcabius terryi and Xaiithoencyrtus fidlawayl 

 are all monoxenotic. With the possible exception of PauHdia 

 peregrma all of these species were introduced quite likely con- 

 currently with their hosts, either at the first or subsequent ar- 

 rivals of the latter in the Islands, and their establishment here 

 was on that account more easily accomplished. 



Anagyrus nigricornis, Aphidencyrtus schizoneurae , Apliy- 

 cus cdberti, Comperiella hifasciata, EncyHus infelix and jba7'- 

 hatus, Helegonatopus pseudophanes, Microterys kotinskyl, 

 Quaylea dliena, Saronotum americanuin and Tanaomastix ah- 

 normis are apparently all polyxenotic in habit. The estab- 

 lishment of such of these as were purposely introduced un- 

 doubtedly was aided by this habit, and this was true probably 

 of most of the other species. Some of them presumably were 

 brought in concurrently with the host or hosts which they now 

 attack, but this is not necessarily true of all, and in fact can 

 not possibly be true of some. 



Peculiarities in the life-history and habits of parasites may 

 also play a large part in aiding or hindering their introduction 

 and establishment in a new environment. Thus Pauridia pere- 

 grina and Blepyrus mexicanus are known to deposit their egg^ 



^ The only exception is Aphycus hesperidum which Mercet claims is 

 an external parasite of Chrysomphalus dictyospermi var. i>innulifer, but 

 I am strongly inclined to believe that the record is based on an error 

 of observa*^ion. 



