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 very 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 generally, it finds food for itself in every country 
and city dooryard. either the San Jose scale, or. in Japan particularly, 
the white peach scale (Dia$pis pentagona)^ on which it also feeds. 
The stock of ladybirds, therefore, is always 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 spraying- 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- 
mately, 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 any other predaceous insect — and 
this is true also of the chalcidid parasites, tho perhaps in a less degree — 
can ever be expected to so thoroly 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 ultimately 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- 
sarily 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 very much to the advantage of even^one to spray 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 anything 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 young 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 L.44<> 
scale insects per day would be destroyed. The appetite of these larvse 
seems to be never satisfied, and they 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 
ordinary circumstances, practise regular spraying operations. 
