INJURIOUS AND BENEFICIAL INSECTS OF CALIFORNIA. 83 



smut fungus grows. This gives the trees a very unhealthy appear- 

 ance and doubtless interferes with the respiration. Much damage 

 is claimed by walnut growers to have been caused by this aphid 

 during the past few years. 



Distribution.— This species occurs throughout the central and 

 southern parts of the State. 



Host Plant.— So far as known it works only upon the English 

 walnut. 



Special Control.— The application of commercial lime-sulphur (1 

 to 20) during the winter months from November to March to kill 

 the eggs has given very good results. A woodland nozzle and high 

 pressure are most satisfactory, though with care the work may be 

 done with an ordinary power outfit. A summer spray composed of 

 a 2 per cent distillate oil emulsion to which is added one part of 40 

 per cent nicotine sulphate ("black leaf 40") to every 1500 parts of 

 the emulsion, has also given good results. 



Natural Enemies.— The most effective natural foe of this louse is 

 the ashy-gray ladybird beetle, Olla abdominalis (Say). 



THE WILD WALNUT PLANT LOUSE 



Callipterus caUfornicus Essig 54 

 (Fig. 66) 



Description.— This louse is often confused with the walnut plant 

 louse (Chromaphis juglandicola Kalt.), which is so troublesome in the 

 walnut orchards of southern California. The difference in markings of 

 the winged females easily separates 

 the two lice. All of the adult females 

 appear to be winged, the young 

 nymphs being the only apterous indi- 

 viduals observed. The adult is bright i 

 yellow in color with antennae, a band 

 on each side of the prothorax, the 

 wing veins, the tibia? and feet dark. 

 None of these markings are pro- 

 nounced in the young. 



Life History.— The life history of Fig. 66.— The wild walnut plant 

 this plant louse is practically the same JK^^gSK? C Gil%iy™nSli: 



as for the Walnut plant louse. (Authors illustration, P. C. Jr. Ent.) 



Distribution. — This species occurs in great numbers upon the wild 

 black walnut throughout the southern part of the State. 



Food Plant.— The plant lice work upon the undersides of the leaves 

 of the California black walnut (Juglans calif ornica). Great colonies 

 may often appear so as to completely cover the foliage and the amount 

 of honey-dew secreted is sufficient to cause smutting, rendering the 

 trees very unsightly. 



M Mr. J. J. Davis has called attention to the fact that only caryella (Fitch) is 

 included in the genus Monellia. In this genus the wings are folded horizontally over 

 the back, which excludes the above species as well as caryw Monell. 



