ACETARIACEOUS PLANTS. — CELERY. 



149 



grubs are the larva? of Tephritis onopordinis. 

 The grubs may be found in the leaves of the 



Fig. 53. 



CELERY -FLY, GRUB, &C. 



celery in June, July, August, September, October, 

 and November, for there are two or more broods 

 of them in the course of the year. The grubs, 

 although less frequently, are found doing similar 

 damage to the leaves of Alexanders and parsnips. 

 When full grown, the grubs descend into the 

 earth, and remain in the chrysalis state till the 

 spring following, when they give birth to the 

 fly. Then the celery-fly may usually be found 

 upon the leaves of the laurel, hovering over 

 flowers, and resting upon palings in the sun- 

 shine, from the middle of May to the end of 

 July." Mr Westwood thus describes it: "The 

 general colour of the body, which is five-jointed, 

 varies from rusty brown to shining black ; head 

 buff, with black hairs ; legs yellow ; thorax 

 (throat) sprinkled with long black hairs ; wings 

 black, with various pale spots ; eyes green. The 

 whole length of the insect is not more than one- 

 sixth of an inch, and its wings, when outspread, 

 barely half an inch across." Mr Westwood sug- 

 gests that a string smeared with bird-lime, and 

 stretched over the celery plants, might catch 

 many of the parents. This is a good idea, and, 

 if carried out, would no doubt entrap many 

 moths and butterflies also, which would be a 

 wholesale mode of lessening the numbers of 

 grubs afterwards. 



Piophila apii (the celery stem-fly), fig. 54. — 

 The discovery of this hitherto undescribed in- 

 sect is due to the author of the article " Ento- 

 mology," in the " Gardeners' Chronicle," 1848, p. 

 332, who thus describes it, and its mode of 

 operation : " The larva burrows into the solid 

 stem and fleshy stalks, working its way up the 

 latter, its tract, as well as itself, being at first 

 almost invisible, from its similarity in colour to 

 VOL. II. 



the substance of the stem ; so that we have no 

 doubt portions of the stalks, although contain- 



Fig. 54. 



CELERY STEM-FLY AND GRUB. 



ing the grub, are often eaten, owing to its pre- 

 sence not being suspected. The eye of the en- 

 tomologist, however, especially if assisted by a 

 moderate lens, easily detects the unwelcome 

 visitor, which may indeed be expected when 

 the solid part of the stem shows traces of being 

 worm-eaten. It would seem, in fact, that it is 

 in the solid part that the injury is commenced, 

 the grubs eating upwards into the more succu- 

 lent stalks of the leaves, leaving their traces in 

 the former visible in their tracts, which become 

 rusty red, owing to the action of the moisture 

 and air upon the grooved surface which they 

 have quitted. By careful examination and re- 

 moval of the leaves, the authors of the mischief 

 may be found in their burrows, in the shape of 

 glossy white cylindrical grubs, with a slight yel- 

 low tinge, having the anterior part of the body 

 pointed, and the hind part obtusely rounded, 

 and marked with two black points, from whence 

 proceed two delicate air-vessels, appearing like 

 threads of gold beneath the transparent skin, 

 and which run along the whole length of the 

 body as far as the segment immediately behind 

 the head, where they form two minute excreted 

 appendages. The hind joints of the body are 

 indistinct, but the fore ones are more distinctly 

 to be traced. The mouth consists of a black 

 horny apparatus, capable, as well as the head 

 itself, of being withdrawn within the subsequent 

 segment, as far as the two excreted lobes of the 

 air-vessels above mentioned. 



" The fly very closely resembles that reared 

 from the cheese maggot. The thorax and abdo- 

 men are entirely jet black, and very glossy, with 

 a very slight brassy tinge, and with fine golden 

 grey hairs scattered over the body. The head 

 is chestnut-coloured, paler near the mouth, and 

 black in the middle above. The eyes and club 

 of the antenna) are pitchy ; the bristle of the 

 latter luteous, or yellowish. The legs, in- 

 cluding all the coxae or joints by which they are 

 attached to the body, are very pale straw yel- 

 low ; the tarsi, especially in the hind feet, some- 



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