CHAPTER IV. 



CHECKS TO INCREASE OF COCCIDID.E, PARASITES, 



ETC. 



THE Coccididse, like all Homoptera, produce great numbers of 

 young ; but their increase does not appear to be as rapid as that 

 of some other families. The numbers of some Aphididse or 

 Alcurodidae produced from a single female in the course of a 

 single year have been calculated at hundreds of thousands, if not 

 millions ; and as many as eleven generations have been produced 

 in little over half a year. Coccids, however, as a rule, do not 

 propagate at this alarming rate. Many, if not the great 

 majority of them, produce in this country but one generation in 

 the year, e.g., Mytilaspis pomorum, Coslostoma z&landicum, &c. 

 Others, such as leery a purchasi, breed more often ; and probably 

 climate has a good deal to do with the frequency, for Mr. 

 Comstock says that in the United States Mytilaspis pomorum 

 breeds once a year in the North and twice in the South. In 

 point of fact, it does not seem possible to lay down any rule on 

 the subject. Unfortunately, Icerya is not only a frequent 

 breeder, but also the most destructive insect of the family in 

 New Zealand. 



The number of young produced by each female seems also to 

 vary. The author has counted from 30 to 80 eggs in the 

 puparium of Mytilaspis pomorum ; as many as 350 in the ovisac 

 of Icerya purchasi, and about the same number of Ccelostoma 

 z<Rlandicum : and a female of Lecanium hesperidum examined in 

 spring contained 93 embryos. These figures do not denote any 

 remarkable fertility; but, as in the majority of cases males are 

 but seldom met with, sometimes even entirely unknown (e.g., 

 Lecanium hesperidum} , it follows that nearly every insect is capable 

 of propagation, and the increase in numbers is therefore more 

 rapid than might be anticipated otherwise. How the females 

 in the species apparently destitute of males are enabled to pro- 



