APPLE SAWFLY. 37 



the case of Codlin Moth) to where infestation is present by 

 the numbers of little Apples which have fallen beneath the 

 tree. The sawfly grubs fall to the ground in the infested fruit 

 in June or July, or as soon as the little Apples are so much 

 injured within that they can no longer adhere to the tree ; 

 and the sawfly caterpillars then make their way out, to go 

 through their changes in the ground. There they form their 

 cocoons, and remain inactive until the following year, when 

 in May the perfect sawflies make their appearance from the 

 buried chrysalids. 



There does not appear to be any record of the caterpillars 

 crawling down the stem of the tree to bury themselves, nor is 

 there (so far as I am aware) any evidence of their dropping 

 from the Apples. But still, as in experiment they have been 

 found to drop (when released from the fruit) from a consider- 

 able height without injury, and as many recently infested 

 Apples are to be found on the trees without caterpillars 

 within, it is presumable that some proportion of the grubs 

 reach the ground by simply dropping themselves down. 



In regard to the depth to which the caterpillars go down 

 into the ground to form their cocoons, this varies according 

 to the nature of the soil. In special experiment made on this 

 subject four inches was the depth at which the cocoons were 

 chiefly found. The first cocoon lay at a depth of two inches, 

 more were found at three inches, and they lay thickly at a 

 depth of four inches.* The cocoons, which are in shape like 

 little balls, and just large enough to hold the caterpillar, may 

 be found formed about a month after the caterpillars have left 

 the Apples, possibly sooner. The caterpillar, however, may be 

 found unchanged within the cocoon, even after the time of 

 Apple blossom in the following year, when the chief attack 

 takes place, the stray flies which then appear presumably 

 depositing on the young Apples when somewhat advanced be- 

 yond their quite embryo state. 



Prevention and Kemedies. — All measures, firstly, to keep 

 the infestation from going down into the ground in caterpillar 

 condition, and next to prevent it coming up in winged form, 

 are most important. 



In the first case, the little Apples should be collected as 

 soon after they have fallen as possible, and burnt. It is little 

 or no use throwing them to a rubbish-heap, from which 

 (unless specially treated) the sawflies would probably fly at 

 Apple-blossom time in the following year to start infestation 



* Detailed observations of Life-history of the Apple Sawfly, by Mr. W. Cole- 

 man, of Cranford, Newport Pagnell, Beds, will be found in my Fifteenth and 

 Sixteenth Annual Eeports of Injurious Insects. — E A. 0. 



