384 



THE PESTS OF GARDEN PLANTS 



leaves on which the colonies are seated, and make an end of them. 

 This enemy cannot be raked in rank and file, but must be taken in 

 detail, as in guerilla warfare. 



CELERY FLY is not amenable to any medicaments, for its larva 

 harbours within the blade of the leaf, in which it causes apparent 

 blisters, which, however, are not blisters, but places deficient of 

 parenchyma or leaf-green, which the insect eats while making itself 

 a home. Dusting newly-planted Celery with lime or soot may do 

 something to prevent the fly laying its eggs ; but when once the grub 

 appears, it should be crushed by pinching the leaf, or the leaves 

 should be picked off and burnt. It should always be remembered, 



however, that the leaves are as 

 much needed by the plant as the 

 roots, and every leaf removed 

 tends to the diminution of its 

 vigour. Our illustration shows 

 the Celery Fly (Tephritis onopor- 

 dinis, Fab.) natural size and mag- 

 nified. This fly is also destruc- 

 - tive to the leaves of Parsnips, and 

 it is called onopordinis from its 

 habit of frequenting the Cotton 

 Thistle (Onopordon Acanthhtni). The larva is pale green, the fly is 

 shining tawny. An Ichneumon Fly detects the larva of the Celery 

 Fly in the Celery and Parsnip leaves, and lays its eggs in the body 

 of the larva. These parasites, named Alysia Apii, therefore tend to 

 reduce the numbers of the Celery Fly. A second insect, named Pachy- 



larthrus smaragdinuS) is also fre- 

 quently destructive to the pupae 

 of the Celery and Parsnip Fly. 



CELERY FLY AND LARVA 

 Tephritis onopordinh 



ONION FLY. Onion crops 

 are sometimes totally destroyed 

 by the larvae of the Onion Fly, 

 here illustrated, with the perfect 

 insect, natural size and magnified. 

 The flies lay eggs in the Onion, 

 close to the earth, and when these eggs are hatched the larvae emerge 

 and eat their way at once into the Onions. In this position they 

 frequently destroy the hearts of whole crops of Onions, This fly also 



ONION FLY AND LARVA 

 Anthoinyia ccparum 



