SCALE INSECTS 311 



cultural quarantine officers are now stationed at various 

 ports and examine all consignments of plants arriving. 

 The number of injurious insects intercepted in this way 

 is amazing, and much harm is prevented ; though it 

 seems hard to a passenger from Japan to have his 

 highly prized little tree destroyed because it has scales 

 on it which he himself cannot see at all ! One needs 

 entomological knowledge and a lively imagination to 

 picture the possible evil which may come from such 

 minute objects. The San Jose scale, which was brought 

 in before the days of quarantine, represents the extreme 

 type of Coccid development. The scale is like a little 

 oyster shell, covering the minute fleshy female insect. 

 This female has no legs or antennae, but has a large 

 mouth, designed for sucking the juices of plants. Her 

 main function appears to be the production of young ; 

 she is inert, unable to move about, a picture of de- 

 generation. The young are extremely small, oval 

 creatures, with six legs and a pair of six-jointed antennae. 

 For a short time they can run about at will. They 

 may be blown about by the wind, or may get from tree 

 to tree on birds or insects. Their free time is short, and 

 presently they have to settle down, for the rest of their 

 lives if females, and begin to develop little scales. Some 

 of them produce males, which are small, flylike insects 

 with long antennae and a pair of wings. The adult 

 males have no mouth parts ; they do not eat. Their 

 sole function is to bring about the fertilization of the 

 females, and this done, they die. 



4. Thus the Coccidae are exceptions to many rules. Evolution of 

 We say that insects have six legs, but many adult scale Coccidae 

 insects have none. We say that Hemiptera have four 

 wings, but female coccids never have any, while the 

 males have only two, or rarely none. How, then, do 



