434 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 10 



There have been about fifty species described in Cahfornia so it will 

 be seen that they are not nearly as abundant as either plant-lice or 

 scale insects. None of the native species have become of great eco- 

 nomic importance and but one injurious species has been imported 

 into the slate. 



Two species, at least, the tomato psyllid, a native of the western 

 states, and the laurel psyllid, a native of Europe, are deemed of suffi- 

 cient importance and interest to warrant a discussion of this kind. 



The Tomato Psyllid *^ 



Paratrioza cockerelli (Sulc) 

 (Plate 20, fig. 1 and fig. 22) 



This insect has been of some economic importance in Colorado for a 

 number of years and still continues to receive consideration from 

 agriculturists of that state. In California it is widely distributed and 

 though little has been known regarding its economic status, it is coming 

 to be noticed as a garden and field-crop pest in many localities. While 

 it cannot be classed as an insect of major economic importance or even 

 one which may ever cause great losses, it often increases in sufficient 

 numbers to injure the infested plants and becomes a source of loss 

 and worry to the grower. 



General Appearance 



Eggs (Fig. 22 D). — The eggs are exceedingly small, elongated-oval, 

 with the attached and decidedly pointed end supported by a short 

 petiole and the free end broadly rounded. The color is transparently 

 white or pale greenish-yellow with a more or less definite orange-colored 

 mass at the middle or base. The surface is normally entirely covered 

 with a fine white powdery wax which gives a decidedly gray appear- 

 ance. The powdery wax is also deposited over the surface of the 

 leaves around the eggs and materially aids in locating them. The 

 average length is about 0.08 mm. They are usually deposited in 

 very great numbers upon the under surfaces of the older well-matured 

 leaves and stand erect or slightly leaning. 



Nymphs (PL 20, fig. 1, fig. 22 G). — The first born nymphs are very 

 small and transparently pale yellow with orange-colored head and 

 abdomen. The color changes somewhat as the insects mature and 

 when ready for the last molt they are pale greenish-yellow with gray 

 and orange markings on the dorsum. Excepting for the fringe of 

 scale-like spines around the margins (Fig. 22 H) the bodies are per- 

 fectly naked. The bodies are very flat, broadly oval and held close 

 to the surface of the leaves when feeding. The excrement is in the 

 form of minute white pellets of honey-dew (PL 20, fig. 1) which are 



