74 THE REPOKT OF THE No. 36 



between different countries, we have introduced not only many useful plants, but 

 the insects which prey upon them. Often in the case of scale insects we have im- 

 ported the scale and left behind some of the enemies which attack it. This gives the 

 scale a tremendous advantage and often before the balance is restored very great 

 damage is done. To restore the balance more speedily the entomologist looks to the 

 native home of the scale to ascertain its most effective enemies. These are then im- 

 ported and bred and liberated in various parts of the infested areas. In some cases, 

 such as the Lady Bird Beetle, belonging to the genus Pentilla, has rendered excel- 

 lent service to the fruitgrower. The chief enemies in Canada are birds, Acarids, 

 insects and fungus parasites. The most effective of these are the Acarids and 

 insects. 



It is difficult to calculate accurately the amount of good service rendered by 

 many of the insectivorous birds. Warblers and Vireos, on account of their aesthetic 

 value and also the fact that they are insectivorous are rarely taken and subjected 

 to examinations of stomach contents. Furthermore their minute size render it 

 almost impossible to observe their actual work. The larger birds, such as the Hairy 

 and Downy Woodpecker, have been secured, stomach contents examined and found 

 to contain, in some cases, hundreds of scales in a single stomach. This is especially 

 noticeable in the case of the very destructive New York Plum Scale. It is highly 

 probable that these insectivorous birds rank first in the control of the larger kinds 

 of scale insects, such as Eulecanium, Coccus and Kermes. 



The mites again deserve a great deal of credit for their very efficient service 

 to the fruit grower, in that they consume large numbers of scale insects all through 

 the season. Some confine their attacks to one particular species, while others are 

 general feeders, attacking a large variety of insect life. There are about eight 

 known species of Acarids in Canada that are in some way associated with injurious 

 forms of scale insects. There are at least, three species working upon the San 

 Jose SQa]e -.He nnsarcoptes malus is commonly found in the St. Catharines district. 

 Species of Monieziella and RliyncholopTius were found feeding upon San Jose at 

 Grimsby, Ontario. Four species were found either feeding upon the eggs or the 

 adult of New York Plum Eulecanium. Three of these species belong to the 

 genus RhyncJiolophus, and the other to the genus Gmnasus. All four undoubtedly 

 help to keep this scale in check. Two species are found attacking the eggs of the 

 Oyster-shell Scale. Tyroglyphis lonnior is very common at Gnelph, and Tlemi- 

 sarcoptes malus at St. Catliarines, Ontario. Another s])ecies helonginr!; to the genus 

 Odlumna was found feeding upon the scale known as Enleranium feicJieri. 



Insect Enemies. 



These, if not the most destructive are at least the most numerous of all (.occid 

 enemies. They represent four orders of insects : the Hymenoptera, Coleoptera, 

 Lepidoptera and Diptera. Mr. Alfred Eastham investigated the parasites of scale 

 insects in Ontario and found twenty-three species belonging to the Hymenoptera. 



Host Relations of Species op Aphelin^ Reared During the Summer in 



THE Vicinity of Guelph. 



Parasite. Host. 



Aphelinus mytilaspidis Lepidosaphes ulmi. 



Chionaspis pinifolise 

 Chionaspis salicis 

 Aspidiotus perniciosus. 

 Aspidiotus ostreaeformis. 



