38 THE REPOET OP THE No. 36 



task of making definite caged tests with large cheesecloth cages over individual 

 bushes. Cheesecloth was placed also over the ground beneath these cages to 

 make counting dead flies practicable and also prevent new adults coming up out 

 of the soil. 



The cages were as follows: — 



Cage 1. — Bnsh sprayed with arsenate of lead in water sweetened with molassee. 

 Cage 2. — Bush sprayed with arsenate of lead in water without sweetening. 

 Cage 3. — Bush sprayed with calcium arsenate in water without sweetening. 

 Cage 4. — Bush unsprayed as check. 



In each cage 60 adults were placed. 



Resttits at end of SO hrs. 



Cage 1. — 13 dead. 



" 2.— 12 " 



" 3.-25 " 



Check " 



Results at end of 52 hrs. 



Cage 1. — ^53 dead. 



" 2.— 51 " 



" 3.— 60 (all) dead. 



Check 8 dead. 



Results at end of 12 hrs. 



Cage 1.— 58 dead. 



" 2.— 60 (all) dead. 



" 3.— 60 " 



Check 18 dead. 



From these tests it seems quite clear that this species of Saw-fly can be 

 poisoned in the adult stage and that molasses is not necessary for the purpose. 

 The question then arises as to when to do the poisoning. It will have to be done 

 before the adults appear in July, and it seems to me the proper time will probably 

 be just before bloom, or just after most of the blossoms are off and the fruit 

 is still so small that there will be no likelihood of the poison being on it when 

 ripe. A second application will possibly be advisable just after picking. Arsenate 

 of lead will probably be the safest poison and if applied heavily without molasses 

 should remain on the foliage for a month or more. Arsenate of lime kills more 

 quickly but would be more likely to injure the foliage, though none of the spray- 

 ing either in cages or on the part of the row I treated myself, even where molasses 

 was used, caused burning. 



I hope to make a careful trial of the poison treatments this coming year and 

 to give a further and more definite report next year. 



Zebra Caterpillars (Ceramica picta). 



In September and October of 1916 there were several turnip fields in Peel 

 County and probably in many other unreported parts of the Province that were 

 severely injured by the Zebra Caterpillar. As it is rare that this insect becomes 

 very numerous I did not expect it to cause much trouble this year, but to my 

 suri^rise it has been very abundant in many counties west of Toronto and has 

 stripped many a turnip field of all or almost all its foliage. Many fields were 

 thus defoliated by the end of September, thus preventing almost a whole month's 

 growth. Cabbages were also attacked. The larva; were found feeding on several 

 other plants. 



