THEIR RELATION TO EACH OTHER 105 



a little black species with one red spot on each wing- 

 cover. About once every decade the scale escapes con- 

 trol, and for a series of three or four years becomes in- 

 creasingly abundant so that tree owners are thoroughly 

 scared and demand remedial measures. Experience 

 has enabled me to assure these owners that when mat- 

 ters are apparently getting serious, the worst is over; 

 because by the end of the third year the Hyperaspis 

 has caught up with its host and almost every scale 



FIG. 48. The signate lady-beetle. 



egg mass contains one or more beetle larvae feeding in 

 and upon it. The year following, scales may be difficult 

 to find and the Hyperaspids are forced to other species 

 upon which they fail to maintain themselves and 

 perish all save a few that find enough congenial food 

 to maintain the species. 



What happens when an insect of this character is 

 entirely freed from its normal check, was demonstrated 

 in California when the cottony cushion scale, I eery a 

 purchasi, was introduced from Australia without the 

 Vedalia cardinalis. In a few years the Icerya had as- 



