8 HYDROCYANIC-ACID GAS FUMIGATION IN CALIFORNIA. 
THE PURPLE SCALE. 
(Lepidosaphes bechii Newm.) 
The purple scale appears to prefer the more moist regions in the 
vicinity of the ocean, as its distribution is confined largely to this 
part of the citrus belt. This insect confines its attacks to citrus trees, 
infesting not only the leaves and branches but also the fruit. Much 
injury results. The young purple scale insects hatch from eggs 
deposited by the adult. The number of broods of this insect in 
southern California has never been exactly determined. Prof. H. J. 
Quayle, of the University of California, is at present investigating the 
life history of this, as well as the other injurious citrus scale pests. In a 
climate like that of southern California, which is never severe at any 
time of the year, there is much overlapping of broods, so that scales in 
all stages of development can be found at almost any time of the year. 
The writer's own observations in the field have shown that there are 
two very noticeable general broods, one appearing in the early spring 
during March or April, the other in the fall, usually about October. 
These broods are much earlier some years than others, depending on 
the nature of the weather. The fall brood of the scale is the most 
injurious, as shown by the fact that trees which at a distance may 
appear entirely healthy one month may have the leaves of a large 
area, or even an entire side, turn yellow and drop off the next month. 
The orchardists speak of this as "firing. " It is due to the attacks of 
the enormous number of young insects which, on hatching, have 
spread about and settled down on those branches immediately 
adjoining the ones previously infested. Trees infested with the 
purple scale seldom present a diseased appearance on all sides. The 
habit of this insect is to frequent the inner and shadier portions of 
the tree, so that sometimes severely infested trees may present no 
visible appearance of this condition on the outside. In the majority 
of cases where the infestation appears on the outside of the tree it 
will be found that it is at or near the northwest corner, which is the 
shadiest part during the day. The attacks are also confined largely to 
the lower part rather than the top of the tree. In long and seriously 
infested trees the insects may spread throughout. 
THE BLACK SCALE. 
(Saissetia olex Bern.) 
The black scale is found more or less throughout southern Cali- 
fornia, yet matures more freely and causes more injury in the region 
adjacent to the ocean than in the hot interior valleys. It occurs on 
a wide range of hosts, including trees, shrubs, and herbaceous plants. 
The commercial importance of the black scale arises largely from 
