to the ground when mature and there form cocoons in which they live till late 

 the next spring, without much harm from the winter flowage even when it is 

 held late. 



The cocoons are whitish, slightly flattened cases of closely spun silk about 

 a sixteenth of an inch long. Those of the second brood usually are attached 

 to fallen leaves or other trash (fig. 65). The maggot changes into a brown 

 pupa and this wriggles out of the cocoon through a slit at one end shortly 

 before the fly emerges. 



Treatment 



The maggots endure submergence longer than it is safe to have the growing 

 vines flooded. 



SANDING 



Ordinary resanding every other year during the fall, winter, or early spring 

 checks the pest nicely on most bogs, but it seldom pays to sand so often if a 

 bog has ample frost protection. The sand either smothers the worms in their 

 cocoons or prevents the emergence of the flies. Fertiliser helps weak vines 

 bud after the attack of the worms, especially on sand bottom. 



DUSTING OR SPRAYING 



Dusting or spraying with DDT materials as soon as scattered cranberry 

 blossoms have opened gives good control by killing the flies as they emerge to 

 lay their eggs. In dusting, 60 pounds of a 10 percent DDT dust to an acre 

 is necessary. In spraying, 3 pounds of 50 percent wettable DDT in 100 gallons 

 of water, 400 gallons to the acre, is advocated. 



Cranberry Sawfly ^4 



This species occurs only on dry bogs and bogs that are not rellooded regu- 

 larly. It hardly ever attracts attention, but its long feeding period probably 

 sometimes allows it to do considerable harm. It is one of the minor drains that 

 must be checked to make cranberry culture efficient. 



Distribution and Food Plants 

 This insect has been found in Massachusetts, New York, New Jersey, Illinois 

 and Wisconsin. Cranberry is its only known food plant. The worms scallop 

 the leaves irregularly. 



Description and Seasonal History 

 The worms winter in rather tough cocoons of coffecbrown silk (fig. 66) 

 among the trash on the bog floor, unharmed by the winter flood. They pupate 

 in early May and the adults usually emerge soon after mid'May and lay eggs 

 so that the larvae appear on the bogs again early in June. About five gen- 

 erations occur, the last worms usually entering their winter cocoons in mid' 

 Oc'ober. The worms develop so irregularly that the broods get mixed by late 

 summer, all stages occurring at once. 



THE EGG 



The female always perches on the edge of a cranberry leaf to lay and puts 

 her eggs in pockets she makes between the upper and lower surfaces and 

 opening at the margin (fig. 67). The pockets usually are placed singly, but 

 sometimes two or more are near together. One or, rarely, two eggs are placed 

 in a pocket and often protrude a little. They are elliptical, watery greenish 



^^ Pristiphora idiota Norton. 



{63} 



