210 



INJURIOUS INSECTS AND FUNGI. 



[Dec. 18.94. 



The maggots make mines or passages in the parenchyma of 

 the leaf, and feed upon its soft juicy substance. The leaf 

 soon contracts and becomes bronzed in colour. After a time 

 it shrivels up and is utterly useless to the plant as a means of 

 respiration and of taking in food from the air. In the case of 

 a celery plant thus infested, the stalks or stems that have been 

 earthed-up, in order to blanch them, cannot properly grow and 

 fill out. Sometimes the plant is killed, or the celery is green 

 and small. As the cultivation of celery is very extensive, some 

 growers planting as much as from 50 to 100 acres, the losses are 

 often most serious. 



With respect to parsnips, the injury to the leaves is the same 

 as in the case of celerj-, and the roots are small, much forked or 

 badly shaped. 



The fly (No, 1) is very small, only about eight lines — the 

 eighth of an inch — in length, and has a wing expanse of not 

 quite half-an-inch. It is of a tawny brown colour or honey 

 yellow, as Meigen terms it, Avith the under part of the body 

 light coloured. The wings have oblique lines of rusty or 

 brownish spots running tlii'ough their upper parts, while the 

 lower parts are hyaline. It has six legs, of a dark yellow hue. 

 When it is at rest upon the plants its wings are upright. The 

 female fly has a long ovipositor with which it places its eggs, 

 ►singly, upon the cuticle of the upper sides of celery and parsnip 

 leaves. Many eggs are laid by one insect. Thev are hatched 

 in about six days, and the larvae (No. 2) from them are pale 

 green, without legs, thick in body, somewhat ])ointed at the 

 head, and square at the tail extremity. When full grown they 

 are close upon a quarter of an inch long. 



In about 14 days, the larva changes into a pupa and either 

 remains in the leaf or falls to the ground. From the pupa 

 (No. 3), which is of a yellowish colour, oval, and much wrinkled, 

 becoming darker later on, the fly emerges in a few days and 

 commences a new series of existence. There are two or more 

 generations in a season. The pupse of the last g^^'neration, which 

 is determined by conditions of weather and food supply, pass the 

 winter in their pupal form in the ground, and m the remains of 

 the leaves or in rubbish near. 



It is worthy of record that larvae of this fly were found late in 

 November in the folds of celery stems, close to the l)ulb-like end, 

 they were in the folds nearest to this, and as the folds were 

 tightly packed round the bulbous end, the larvae must have 

 mined their way through and down parts of the stems, as it was 

 impossible that they could have merely fallen down from the 

 leaves. Mr. Theobald, of the Wye Agricultural College, also has 

 recently found the larvae of this fly in this poaiti n. This dis- 

 covery was made while closely examining celery rdants for the 

 larvae of the Celery Stem Fly, Piophila apii, another trouble- 

 some pest of celery, and it appeared ' from th position of the 

 Tephritis larvae that they were feeding upon the sweet and 

 softer parts of the blanclied stems. 



