94 INSECTS WHICH PREY UPOX AGRICULTURAL PLANTS. 



fly injure the cabbage and turnip crop by eating passages in the 

 stem and roots, and thus inducing disease or decay. Tliey are 

 whitish, round, and apodal, with tapering head and bkint tail, 

 and when full grown are about one-third of aa inch long. They 

 turn to pupae in the earth, and issue as flies of an ashy-grey 

 colour in about a fortnight or three weeks ; the later ones, how- 

 ever, lie dormant till spring. The affected plants turn yellow 

 and lade in the heat of the day. The application of lime has 

 been found beneficial, and two crops of cabbages should not be 

 taken in succession. 



Another pest very similar to the above is the Eoot-eating Fly 

 {Anthomyia raclicum). The grubs of this variety are of a yellow- 

 ish-ochre colour, but otherwise the economy of the two insects 

 and the appearance of the flies are very much the same. 



Trichocera hiemalis (the Winter Turnip Gnat). — The maggot 

 of this insect is found in the diseased excrescences on turnips 

 known as " Anbury." It is not the cause of this disease, how- 

 ever, but simply an accompaniment of its progress ; " clubbing" 

 in cabbages being a similar affection, and most likely due to the 

 same cause. The larvoe are slender, shining, and pale yellow in 

 colour, scarcely half an inch long, thick at the tail, where there 

 are two browm spots, and pointed at the head. The imago much 

 resembles a miniature crane-fly, and is of an ashy-grey colour, 

 the wings, which are irridescent, being folded over one another 

 in repose. 



Drosopliila flava and Phytomyza nigricornis are the " Turnip 

 Leaf Miners." The maggots of these insects eat out the " p)aren- 

 chyma" or cellular tissue of the leaf — the former (yellow variety) 

 on the upper side, and the latter (slate coloured) on the under 

 — causing it to have a blistered appearance. The flies are about 

 one-eierhth of an inch in length ; thev do no material damage. 



Tcphritis onoporclinis (the Parsnip and Celery Leaf-Miner). — 

 This is a very lively little fly, which delights in sunshine, and is 

 very abundant from May to July. The wings, which expand 

 nearly half an inch, are carried erect when walking, and are 

 irridescent but spotted with brown. The body is of a shining 

 tawny colour, with a few black spots over the head. The female 

 has a broader abdomen than the male, and is provided with a 

 long retractile ovipositor. She deposits her eggs singly under 

 the cuticle, and the little green maggot eats out the paren- 

 chyma, causing the blisters. It grows to one-third of an inch in 

 length, and either turns to a pupa in the leaf or falls to the 

 ground and does so in the soil. An ichneumon fly, the Alysia 

 apii, keeps it in check. This is of a pitchy black shining 

 colour, one-eighth of an inch in length, and the expanse of the 

 wings one-third of an inch. 



Chlorops tceniopus (the Eibbon-footed Corn Fly. — An insect 



