91 



Southern California is separated by a range of mountains into a 

 comparatively narrow fertile coast region and a dry interior A^alle\', 

 consisting of a high plateau, northward the Mohave Desert, and south- 

 ward the low Colorado Desert, dipping in one place below the level of 

 the sea. There is also an insignificant fertile strip along the Colorado 

 River which is quite tropical. The coast region is the California 

 mostly known to Eastern people. Here is where the great orange 

 and lemon orchards are found. The summers are not as hot as are 

 those of the great valley to the north, because of the influence of the 

 ocean. Thus the shipping of early fruits is from the north to the 

 south; even oranges, which ripen in winter, are being shipped from 

 northern California fully a month earlier than from southern Cali- 

 fornia. The insect fauna of this region is enriched by many Mexican 

 forms, and differs strikingly from that of the great valle3\ Econom- 

 icall}'^, most of their problems are as different as are their practices. 



The central portion of California, along the (^oast, consists of numer- 

 ous valle3\s, each famous for the perfection of some product. The 

 apple, prune, and wine grapes, for instance, are here at their best. 

 South from San Francisco the insect fauna is very distinctive, with 

 numerous peculiar local forms, some of considerable economic impor- 

 tance, while north of the bay the fauna shades off on the one hand with 

 that of the great valley, and on the other with the north coast region. 



The northern part of the State is mountainous or high lava beds. 

 To the eastward and along the coast is a rather narrow fertile region 

 having very heavy rainfall. Here dairy interests predominate. The 

 fauna is practicall}" the same as that of Oregon. 



To bring out more strikinglj^ the economic significance of these 

 divisions, let us now review some of the more injurious insects. 



SCALE INSECTS. 



Scale insects have attracted more attention in California than has any 

 other group. The most injurious species at the present time is the 

 black scale {Lecanium olece). In the south it is most troublesome on 

 oranges and lemons, although it is also bad on olives and deciduous 

 fruits. In the north it is injurious to olives and deciduous fruits in the 

 coast valleys onh', scarcely appearing in the great valley, which seems 

 to be too dry for it. It is chiefly against this insect that fvmiiga- 

 tion with hydrocyanic-acid gas is practiced, but only as it occurs on 

 citrus trees. On deciduous trees resin-soap wash in winter is chiefly 

 depended upon, but it is unsatisfactory on citrus trees. On these trees 

 fumigation has come to be considered the only riMnedy. Some time 

 ago a good deal of stii^'was made about the work of an Australian 

 ladybird {RTiizobius ventralis)^ and possibly all present may not know 

 that it has in no way duplicated the results produced by the Yedalla 

 cardinalia on the cottony cushion scale {Icerya purclimi). The other 



