THE HOMOPTERA 213 



crawling young on an infested tree, from the time the first one appears 

 until reproduction is stopped by cold weather. Assuming the production 

 of four full generations in a season, equally divided between the sexes, 

 and with no loss in number from death by accident or other causes to 

 reduce the number produced, we have a total of 3,216,080,400 in individ- 

 uals as the descendants during one season from a single pair. Fortu- 

 nately, many never reach maturity, or an infested tree would often 

 be sucked dry before winter. 



The San Jose* Scale has a number of parasites which are sometimes 

 quite effective, destroying a large per cent of the scales in some localities, 

 but with such an enormous power of increase of the pest, even a high 

 degree of parasitism fails to give the relief needed. A few predaceous 

 insects are also known, which feed upon the 

 scale. Most noticeable among these is the 

 Twice-stabbed Lady Beetle (Chilocorus bivulnerus 

 Muls.), a small black beetle (Fig. 206) with two 

 red spots. It is nearly circular in outline, very 

 convex and is about one-eighth of an inch long. 

 A fungous disease also attacks the scale, par- 

 ticularly in the South, but parasites, predaceous FlG a 206 ._ Twice . stabbed 

 foes and diseases together, generally fail to hold Lady Beetle (Chilocorus bi- 



it entirely in check. vulnerus Muls.) : a, adult; b 



^ .,.__. larva enlarged: real length 



A lady beetle closely resembling the Twice- shown by the hair lines, 

 stabbed Lady Beetle is an enemy of the scale in W Sanderson and 



Jackson, Elementary Ento- 



China, the native home of the pest, and this moiogy. after RUey.) 

 insect has been brought to the United States 



with the hope that it might do effective work here, but thus far, for 

 various reasons, it has failed to accomplish much. 



Control. Spraying as for the Oyster-shell Scale is useless, for that 

 treatment is based upon the destruction of the delicate, crawling young, 

 by one or at most two applications. With the San Jose* Scale, however, 

 the young do not all appear at about the same time, but are present 

 practically from May or June according to the latitude of the locality, 

 until winter. To use this method successfully therefore would require 

 spraying about every 2 weeks or so for a period of at least 5 months 

 a treatment manifestly impracticable. 



Stronger materials are therefore used, during the dormant season, 

 when the tree is least liable to injury by the spray, and when a more 

 thorough application can be made, the leaves having fallen. For this 

 purpose the lime-sulfur wash and miscible oils are generally used (see 

 Chapter VIII). At times injury to the trees has been observed following 

 the use of miscible oils, but on the other hand these materials spread 

 better over the tree than the lime-sulfur. Many persons now make a 

 practice of spraying every third winter with miscible oil, but using the 

 lime-sulfur at other times. 



