68 THE SAX JOSE OR CHINESE SCALE. 



widely distributed and is doing so much damage to orchards, it is still 

 far from being universally present, and occurs after all in a Aery scat- 

 tering way in orchards here and there, with often 20 or 30 miles 

 between places of infestation. In Japan and China, where the Chilo- 

 corus occurs rather generall}^, it finds food for itself in ever^^ country 

 and city doorj^ard, either the San Jose scale, or, in Japan particularly, 

 the white peach scale (Dias-pi-'^ pentagonci)^ on which it also feeds. 

 The stock of ladybirds, therefore, is alwa^'S kept up in greater or less 

 numbers, ready to take hold of any unusual scale increase. In this 

 country, if the local food supply is stopt by spraj^ing operations or 

 exhaustion, the ladybird necessarily dies, and very rarely will go far 

 enough to find another infested orchard and a new food supply. Ulti- 

 mateh% when the San Jose scale occurs everywhere, predaceous lady- 

 birds like the Asiatic species will undoubtedly become much more 

 useful than they are under present conditions. 



Neither the Asiatic ladybird nor an}^ other predaceous insect — and 

 this is true also of the chalcidid parasites, tho perhaps in a less degree — 

 can ever be expected to so thorolj" exterminate the San Jose scale as 

 to give sufficient protection for commercial orchard purposes, where 

 absolutely clean or unspotted fruit is an essential. Predaceous and 

 parasitic insects can only survive in connection with their host species, 

 and therefore ultimatel}^ there must be a natural balance which will 

 fluctuate from year to year or period to period, in which alternately 

 the parasite and the host insect get the upper hand, but both neces- 

 sarilv being continuously present. Where substantially clean fruit 

 must be had, as for shipping and export purposes, spraying or some 

 other direct means of control must be practised; and now that an 

 inexpensive tree wash for the San Jose scale has been discovered, it 

 is ver}^ much to the advantage of everyone to spra}^ regularly, rather 

 than trust to control by natural enemies. 



The importation of the Asiatic ladybird and the action of other pre- 

 daceous enemies and of parasites can not, however, work an3"thing but ^ 

 good. These feed upon or parasitize and destroy scale insects and 

 will ultimately greatly reduce the virulence of the attacks of the San 

 Jose species. The larva of the Asiatic ladybird was observed to eat 

 the 3"oung of the San Jose scale at the rate of five or six insects to the 

 minute, and even on an average of but one a minute a total of 1,110 

 scale insects per da}^ would be destroyed. The appetite of these larvae 

 seems to be never satisfied, and the}^ are eating practically all of the 

 time. The adults also feed actively on the scale. In addition to their 

 greater or less efficiency in generally checking the rapid multiplication 

 of the San Jose scale, they and other natural enemies will ultimately 

 be of special service in the control of the scale in private grounds and 

 in small orchards and gardens the owners of which would not, under 

 ordinar}" circumstances, practise regular spraying operations. 



