110 INJURIOUS AND BENEFICIAL INSECTS OF CALIFORNIA. 



enemies is only occasionally seen in some localities. However, in 

 others it may become serious for brief periods or until the natural 

 enemies find it. 



Food Plants.— Acacia, alfalfa, flowering almond, apple, apricot, 

 castor bean, Australian blackwood, boxwood, cedar of Lebanon, 

 chrysanthemum, citron, cypress, fig, geranium, goldenrod, grape, 

 grapefruit, Bermuda grass, sweet gum, hackberry, iron-weed, knot- 

 weed, lambsquarters, laurel, lemon, locust, magnolia, nettle, night- 

 shade, holly oak, laurel oak, white oak, orange, trifoliate orange, 

 peach, pear, pecan, pepper, pigweed, pine, Pittosporum, poinsettia, 

 pomegranate, potato, purslane, quince, ragweed, rose, spearmint, sun- 

 flower, verbena, English walnut and willow are attacked by the cot- 

 tony cushion scale. 



Control.— Artificial control by sprays and fumigation is not usually 

 practiced, because of the efficiency of natural enemies. This is the 

 one case where nature nearly always controls perfectly a serious pest. 



Natural Enemies.— For convenience the natural enemies of this 

 scale are classed under two headings as predaceous, or those actually 

 devouring the host, and as parasitic, or those feeding- on and living 

 within the body of the host. 



Predaceous Enemies.— The common vedalia (Noviits cardinaUs) and 

 the Koebele's ladybird beetle (N. kcebelei) are most responsible for 

 keeping the cottony cushion scale in complete subjection. In many 

 localities the former is the most efficient, but in some places, and espe- 

 cially in Ventura County, the writer found the latter doing more of 

 the control work. 



While these ladybirds are usually present in limited numbers in 

 most sections, yet at times they completely disappear and the cottony 

 cushion scale increases so as to cause considerable damage before the 

 beetles can be re-established. It is always well to keep a close watch 

 of the pest, and if it appears without being accompanied by the larvae 

 of the ladybird beetles, adults should be obtained and liberated as 

 soon as possible. 



Parasitic Enemies.— There are several internal hymenopterous 

 parasites of this scale, including Ophelosia craivfordi, Thoron opacus 

 How., Coccophagus californicus How. and Encyrtus dubius How. 69 

 The dipterous parasite, Cryptochcetum (Lestophonus) iceryce Will., is 

 very common in the southern part of the State, and often does remark- 

 able work. In the year 1913 Mr. A. S. Hoyt reported a splendid 

 cleanup of the scale in Los Angeles County by this parasite. 



•Insect Life, l. p. 270, L889. 



