270 



be present. In San Diego county adults and eggs have been found 

 on the trunk from the surface of the soil to a depth of 6 inches. Spring 

 infestation reaches a maximum from April to June, while autumn 

 infestation begins in September. A Ust of 43 host plants is given 

 including : — Gossypium peruvianum (cotton), Citrus medica var. limon 

 (lemon), Solanum tuberosum (potato), C. aurantium (orange), Cuourhita 

 pepo (pumpkin), etc. P. bakeri is constantly widening its range in 

 California. The Hst of 29 host plants of this species includes apple, 

 lemon, pear, walnut, etc. The incubation period is eight days in summer. 

 In the female the third moult occurs about 42 days after hatching and 

 oviposition begins several weeks later. In the male the cocoon is 

 formed from one to two weeks after hatching, the adult emerging after 

 nine days. 



P. citrophilus has been found in one locahty only, near Uplands, 

 San Bernardino county, into which it was probably introduced in 1910. 

 The host plants include Rheum rhaponticum (rhubarb), Grevillea 

 robusta (silk oak), orange, lemon, walnut, potato, etc. The habit of 

 gathering in clusters, noticeable in P. citri, does not occur in this 

 species. The number of eggs deposited by a single female averages 

 533, while the period of oviposition ranges from 7 to 10 days. In the 

 female the third moult occurs 40 days after hatching ; in the male 

 the cocoon is begun about 25 days after hatching and the adult emerges 

 from 9 to 11 days later. The first generation of any size during 1914 

 hatched in March and reached maturity during the latter part of April. 

 The second generation began to appear about 1st May and reached 

 maturity early in June. Migration of the females was observed at this 

 time. Adults of the third generation appeared in the latter part of 

 July and the first week in August ; their numbers were much less than 

 those of the previous brood. Adults of the fourth generation were 

 observed about 1st October, after which date oviposition took place 

 irregularly. All stages were found on citrus during the winter, though 

 adult females were very scarce, and development appeared to be 

 greatly inhibited. Infestation upon the leaves and roots of rhubarb 

 was very heavy during the winter. The distinctness of the generations 

 throughout the greater part of the year should be of value in deter- 

 mining methods of control and the time of appHcation. P. adonidum, L. 

 {longispinus, Targ.) is a common greenhouse pest. On citrus trees it is 

 confined to the coast counties of CaUfornia. The host plants include: — 

 Citrus medica var. genuina (citron), Ficus carica (fig), lemon, Mangifera 

 indica {niSingo),Opuntia sp, (prickly pear), PAorm*Mmiewaa: (New Zealand 

 flax), etc. This species is viviparous and the rate of reproduction is 

 about half that of P. citri. Mortahty was very great in the first larval 

 period. The average period required by the females to reach the third 

 stage was 44 days ; larviposition began from 10 to 15 days later. 



Parasitic and predaceous enemies of mealy bugs in Cahfornia include 

 the Coccinelhds, Scymnus bipunctatu^, Kug., introduced from the 

 Philippines, Hippodamia convergens, Guer., and Novius cardinalis, 

 Muls. ; Pseudaphycus anglicus, How, reared from P. citrophilus ; and 

 the predaceous larvae of Hemerobius pacijicus, Banks, and Leucopis 

 bellula, Will. 



Investigations into the control of mealy bugs by means of fumigation 

 with hydrocyanic acid gas show that this method is not to be recom- 

 mended. P. citrophilus was more resistant than all the other species 



