120 INSECTS AFFECTING VEGETATION 



The life round of the insect, briefly, is as follows : The winter is 

 passed in the mature larval stage as a thin, elliptical, scale-like object 

 on the under sides of the leaves. Early in the spring the transforma- 

 tion to the pupal stage occurs, this stage differing but slightly from 

 the larval in appearance. The adults begin to appear by the middle 

 of March and continue to emerge through April. The eggs deposited 

 by this brood require about three weeks for development, hatching 

 into larva} from the middle of April to the 1st of May. The adults 

 of the second brood begin to emerge by the middle of June and con- 

 tinue to appear until the middle of July. Between the middle of July 

 and the middle of September a third brood is developed, the larvae of 

 which, hatching about the last of October, carry the insect through 

 the winter. The number of eggs laid by a single female is in the 

 neighborhood of twenty-five, and they are placed, by preference, 

 upon new leaves, but all of the plant is taken when the multiplication 

 of the insect makes it necessary. The young larva is active, resem- 

 bling closely the larva of a true scale insect. The life of the adult 

 ranges from ten to twenty days. 



The most satisfactory remedies for this insect, as demonstrated 

 by Messrs. Swingle and Webber, are the kerosene and resin washes 

 and hydrocyanic acid gas. The treatments may best be made dur- 

 ing the winter, between December and March, and again, if neces- 

 sary, in May, and also in August or early in September. Two or 

 three applications may be made in the winter. The application in 

 August is made if the sooty mold is found to be spreading to the fruit. 

 Since the insect lives on the under sides of the leaves almost exclu- 

 sively, it is of prime importance that the under surface be thoroughly 

 wetted with the spray, and it is necessary that the tree be opened up 

 by pruning. Fumigation with hydrocyanic acid gas is also a ready 

 means of destroying this insect. It is undoubtedly kept more or less 

 in check by parasitic and predaceous enemies, and is subject to at- 

 tack by several fungous diseases, which may be of occasional value 

 in preventing its undue multiplication. 



The Rust Mite of the Orange and the Silver Mite of the Lemon. 

 This mite is an enemy of both orange and lemon, affecting these 

 fruits in a somewhat different way. For many years this mite was 

 known only in Florida, and its injuries were notable only in the case 

 of the orange. It is probably native to the Florida peninsula, pos- 

 sibly having originally some food plant other than the orange. 



The lemon and orange groves of California were for a long time 

 entirely free from the attacks of this mite, but about 1889 some car- 

 loads of citrus trees were taken into California from Florida and 

 planted, without careful inspection, in the Rivera and San Diego 

 JBay districts. This shipment of trees brought with it, unfortunately, 

 two or three of the Florida scale insects, and also this rust mite, which 

 has gained a foothold in the important lemon districts about San 

 Diego, and is now one of the worst pests the lemon grower has to deal 

 with. For a number of years the effect of its attacks in California 

 was ascribed to a fungous disease, and it was not until the writer vis- 

 ited the lemon districts about San Diego Bay in 1896, and identified 



