268 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 10 



the measure of success it will achieve will depend largely upon how 

 completely these requirements are fulfilled. In the first place it must 

 fill a gap in the natural control of the host insect, that is to say it must 

 not attack a stage of the host that is already subject to heavy attack 

 by other parasites. In other words, it must form a new element in the 

 biological complex surrounding the pest. The second requirement is 

 that it must be able to adapt itself and thrive under its new environ- 

 ment, not only in relation to climate but in relation to artificial condi- 

 tions which are brought about by man. At the present time Paralep- 

 tomastix abnormis seems to be all that could be desired in this direction. 

 There is no parasite occurring in California which effectively destroys 

 the first and second stages of the mealy-bug. These are eaten to a 

 large extent by predaceous insects, but the parasitized individuals 

 after they have reached a certain degree of development are refused by 

 these predators. This has been observed frequently in the orchard, 

 large numbers of the mummies being found in trees where the mealy- 

 bugs are severely attacked by ladybirds and lace-wings. Its adapta- 

 tion to environmental conditions is almost perfect. Coming from 

 Sicily, it finds here a climate almost the exact duplicate of the one 

 where it originated. By passing through two winters quite as severe 

 as the average — if one may correctly speak of a California winter as 

 severe — it has proven itself able to withstand our lowest temperature. 

 At Marysville, adults were collected in large numbers a week after 

 two freezes. It has also proven its ability to undergo successfully the 

 hot dry summers of the interior valleys of this state. In our citrus 

 orchards, many of which are infested by Black, Red and Purple Scale, 

 it must be able to survive fumigation for those pests. In many of the 

 orchards under observation it has successfully passed through two 

 fumigations, probably as larvae and pupse within the young mealy-bugs. 

 Spraying does not destroy it, excepting where it is successful in killing 

 the mealy-bugs. 



The question now arises as to what we may rightfully expect from 

 the introduction of this parasite. It is now thriving and increasing 

 rapidly in all the field colonies. The remarkable way in which it has 

 increased during the short time since it has been introduced, the fact 

 that it has proven itself adapted to environmental conditions, and the 

 fact that it fills a gap in the natural control of the host, justifies, I be- 

 lieve, the hope that it will become of great economic value. It is too 

 much, of course, to expect that this parasite alone will be able entirely 

 to control the Citrus Mealy-bug, but its introduction will certainly 

 prove an important step toward that desired end. Time alone will 

 show its true worth to the citrus industry. 



