22 



Young branches thickly infested by this species soon present a 

 gnarled, knotted, and stnnted appearance, and if everything is favorable 

 to the rapid increase of these scales the tree is finally killed by them. 

 They appear to have a discrimination in relation to their food plants 

 that is difficult to account for. I have on more than one occasion seen 

 Leconte pear trees growing in the midst of other varieties of pear trees 

 which were thickly infested with these scales, and yet it was impossible 

 to find even half a dozen specimens of these scales on the Leconte pear 

 trees. I have also been informed that the Black Tartarian Cherry tree 

 enjoys the same immunity from the attacks of these pests, even when 

 completely surrounded with badly infested cherry trees. 



Among insect enemies the most common and widely distributed 

 species is, perhaps, the Twice-stabbed Ladybird referred to above in 

 the chapter treating of the Eed Scale. I have frequently seen infested 

 pear trees upon which these ladybirds occurred in large numbers, 

 still I never knew of an instance where even a single tree had been en- 

 tirely or even very nearly freed of the scales by these ladybirds. 

 Another ladybird which also attacks the San Jose" Scale is the small 

 Scymuus referred to in the chapter above mentioned, but this species, 

 like the preceding one never occurs in sufficient numbers to entirely 

 exterminate the scales. 



Of internal parasites I have bred from these scales large numbers of 

 small, four- winged Chalcid flies known as Aplielinusfuscipennis Howard, 

 a parasite that appears to be quite a general feeder, as it has been bred 

 from at least half a dozen different kinds of scale-insects belonging to 

 species which are protected by a shell or scale. Although occurring in 

 such large numbers, still this parasite is not able to keep the scales in 

 check. It doubtless breeds throughout the year, as I have bred speci- 

 mens as late as the 10th of November. Although I have never bred 

 any other kind of internal parasite from the San Jose Scale, still it 

 would appear that other kinds attack it in the northern part of the 

 State. On the 31st of March of the present year I received from E. 

 M. Ehrhorn, of Santa Clara County, two different kinds of Chalcid 

 flies for naming, and in the accompanying letter occurred the state- 

 ment that both of these parasites had been bred from San Jose Scales. 

 These parasites proved to be the Chalcid flies, known as Aplielinus 

 mijtttaspidis Le B. and Coccophagus citrinus Craw. 



It appears that certain conditions of the climate affect these scales in 

 an injurious manner, just as is the case with several other kinds of 

 scale-insects. A few weeks ago Mr. C. H. Eichardson, of Pasadena, 

 one of the county inspectors of fruit pests, showed me several pear 

 trees in that locality which a year ago were very thickly infested with 

 these scales, as was evidenced by the gnarled appearance of the branches 

 as well as by the dry scales still adhering to the trees. After a care- 

 ful examination of these scales scarcely a live one could be found. Mr. 

 Eichardson assured me that these trees had not been treated with any 



