112 INSECTS AFFECTING VEGETATION 



to repeat the application once or twice at intervals of two or three 

 weeks to effect anything like extermination. 



The Red Scale of Florida. This is another scale insect of world- 

 wide distribution. As an orange scale it is not a very serious pest on 

 trees grown out of doors, but on trees grown in conservatories or un- 

 der glass it is very apt to thickly infest the leaves and fruit. It has 

 a very wide range of food plants and is one of the commonest of scale 

 insects. This and the following species differ from the Mytilas-pis 

 scales in being nearly circular in general outline, with the molted 

 skins in the center of the scale instead of at the small end. The color 

 of this scale is a rich reddish brown, almost black. The central por- 

 tion, however, is much lighter, giving the appearance of a dark ring 

 with a light center. The number of generations can not be accurately 

 given, breeding going on throughout the year, but undoubtedly in 

 greenhouses and tropical regions six or seven generations are not 

 unusual, and in subtropical regions five generations may be safely 

 counted. It seems never to have attracted any attention as an enemy 

 in the orange and lemon groves of California, the dry climate evi- 

 dently not suiting it. The moist climate of Florida and the Gulf 

 region seems more favorable to it. 



The Red Scale of California. This species is entirely distinct 

 from the red scale of Florida. Its name comes not from the covering 

 scale, as with the Florida species, but from the fact that the body of 

 the mature female turns a reddish brown and shows through the thin 

 transparent waxy scale. This insect, although for years very com- 

 mon and destructive in the groves of southern California, and enjoy- 

 ing also a cosmopolitan distribution, has, curiously enough, never ap- 

 peared in a destructive way elsewhere in this country. Its origin is 

 a matter of some uncertainty. It is now widely distributed, and has 

 undoubtedly been a scale pest in oriental countries for centuries. It 

 is not limited to citrus plants, but may occur on almost any plant 

 growing in tropical or subtropical regions. It is the most destructive 

 and injurious of all the scale insects affecting the orange in Califor- 

 nia, being especially troublesome in the districts about Los Angeles. 

 So far no effective parasites or predaceous insects have been found to 

 combat it. It is controlled by the oily washes, and also by the gas. 

 treatment. The young are born free, or, in other words, the insect is 

 semi-oviparous, and therefore any wash which will kill the old scale 

 will destroy the young also. 



This insect has, in California, a rather well-marked variety, 

 known as the yellow scale. This variety does not differ in any struc- 

 tural feature from the red scale, but the mature insect remains yel- 

 lowish in color. This variety is attacked by quite a number of para- 

 sitic flies, which keep it more or less in check, so that it is not, as a 

 rule, so abundant as the red variety. 



The Oleander Scale. This species is not distinctively an orange 

 pest. It occurs on a great variety of plants and has a world-wide dis- 

 tribution. It occasionally occurs on the lemon and orange, espe- 

 cially in California, not apparently being so likely to attack this 

 plant in Florida. It is a very delicate scale, with a very thin waxy 



