ENTOMOLOGY IX OUTLINE HEMIPTERA. OO 



This two-year life round is not necessary to the existence of the 

 species, and the root form may and generally does go on in successive 

 broods year after year, as in the case with European vines, on the 

 leaves of which galls rarely occur. Under exceptional circumstances 

 all of the different stages may be passed through in a single year. The 

 young from leaf galls may also be easily colonized on the roots, and it 

 is probable that the passage of the young from the leaves to the roots 

 may take place at any time during the summer. The reverse of this 

 process, or the migration of the young directly from the roots to the 

 leaves, has never been observed/' 



We have dealt somewhat extendedly with the aphids, because they are 

 among the most serious pests of the farmer and fruit-grower in our 

 own State, as they are elsewhere in the Union. 



Family Aleyrodidse. In the aleyrodes we have a connecting link 

 between the aphids and the scale insects. In the early stages of their 

 lives, the larval form, the aleyrodes are true scale-bugs, and very 

 strongly resemble certain species of Lecaniums. For a long time, mem- 

 bers of this family were classed 

 with the Coccids, but owing to very 

 marked differences in the mature 

 insects were erected into a separate 

 family. They are very small in- 

 sects, and in the larval form are 

 sometimes quite pretty, having a 

 dark center and being surrounded 

 by a fringe of white, waxy fila- 

 ments. In the mature stage, both 

 sexes are winged, herein differing 

 from the Coccida?, in which only 

 the male acquires wings. In this 



stage they are small, white, four-winged flies, very strongly resembling 

 minute moths. The wings and bodies are covered with a whitish pow- 

 der, resembling flour. We have several species of this family in Cali- 

 fornia, and they may be found quite commonly on the under side of 

 the leaves of fuchsias, nettles, iris, and other plants. Where very num- 

 erous, they fly off in a white cloud like a cloud of dust when disturbed. 

 None of our native species are especially injurious, but in Florida 

 and other of the Southern states the Aleyrodes ritri (the white fly), 

 a species found upon citrus fruits, has proven a very destructive and 

 dangerous pest and one that it has not been found possible to control. 



Family Coeeidse (Scale-bugs, Mealy-bugs, etc.). We now come to a 

 family more widely known, and, in California, more generally destruc- 

 tive than any other of the insect tribe. It is a very large family, 



FIG. 54. White.flies(.4i/rode*sp.). Natural 



size and riilurjred. 



