Rhizobius ventralis (Black ladybird). (Plate IV, Figs. 3, 3a, 36.)
This is also an Australian ladybird, introduced by the State Board of
Horticulture through Mr. Koebele, and is one of the natural enemies of
the black scale (Saisseta [Lecanium] oleae). This ladybird was intro-
duced for work on the black scale, and was generally distributed by
the State Board of Horticulture wherever that pest was found. It was
one of the most promising of the many importations of beneficial insects
and took hold of its work with a vigor that gave promise of soon extir-
pating one of the worst of the California scale insects. Wherever it was
introduced in the coast counties of the State, it increased with wonderful



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BUG VS. BUG. 11

rapidity and the scale as rapidly disappeared, and in those sections it
still continues to do good work, but efforts to establish it in the interior
counties have not met with as good success, the heat probably being too
intense for the young larvae. This insect, however, is well established
all over the State, and in many sections is as abundant as any of our
native species. Wherever it is abundant, it is a chief factor in keeping
in check the destructive black scale.
Oreus australasia, Boisd. (Six-spotted blue ladybird). (Fig. 3.)
This is one of the most beautiful of the introduced species. Like most



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Oncus au»tbauasi/«. Boisd. fmaQniriad); la. Diuomatural •!>•):
t Pupa anvclopad tn larval »kln; 8a. Dilio (natural «ii«);
§ Larva; 8a. Diuomatural tizei.
FIG. 3. Orcus australasia.
