DISEASES AND INSECT PESTS 217 



gallon of tepid water, churned into a milky liquid, can 

 be employed without any scorching effect, and a weak 

 solution of quassia chips in soapy water, or one of the 

 quassia insecticides advertised in horticultural journals, 

 is an excellent remedy. 



Sawflies. — Far more destructive than the Aphides 

 is a large family of pests called the Sawflies (Tenthre- 

 dinidece). Many species are found in rose gardens ; they 

 are all armed with a saw-like contrivance with which 

 they cut up, eat, or destroy the leaves, and, in some 

 cases, the soft herbaceous twigs produced by a healthy 

 plant. 



The yellow larva of one of the Sawflies (Pcecilosoma 

 candidatum) voraciously devours the young foliage, and, 

 as soon as its appetite is appeased, bores into the soft 

 pith of the branches and causes them to wither and die. 

 When this sign of its presence is perceived, cut off each 

 twig which contains the grub and burn it. Insecticides 

 are of little avail, but if used in May and June they will 

 help to keep off the tiny, black, hairy fly with spotted 

 head and thorax, and prevent it from depositing eggs 

 on the bushes. 



Other Sawflies, the Hylotomce, are leaf-eaters. Hylo- 

 toma rosea is a small fly of dirty yellow colour and having 

 a black head and thorax ; the larva, or grub, is green, 

 with yellow and black spots, and is hatched from the 

 egg in a few days. It destroys many of the leaves and 

 before it arrives at the pupal or quiescent state spoils 

 the elegant appearance of the foliage ; it pupates in the 

 ground. 



