Tephritis onopordinis. Celery Fly. This insect causes blisters on the leaves of celery by puncturing them, and depositing its eggs within their tissue. Mr. Curtis observes that, -

"On examining these blisters they are found to be considerably inflated, and, on holding them up to the light, a maggot may be seen moving between the thin and somewhat transparent cuticles, where it has been consuming the parenchyma. Those parts of the blisters where it commenced its operations being withered, they become ochreous or brown; and the other portions, but recently deprived of the pulpy substance, partake of a pale green tint. In this way one maggot will form a patch of more than an inch in diameter before it is full grown.

"The larva; are of a glossy pale green, with the alimentary canal shining through the back; the head is attenuated, and the tail obtuse, with a few tubercles. The maggots leave their habitations and probably enter the earth to undergo their transformation to the pupa. The male flies are shining ochreous, with a few black bristles on the head and thorax, which are dark ochreous; the lower part of the face and horns is yellowish; the latter droop, and are furnished with a fine bristle or seta, which is black, except at the base. The eyes are deep green; the body, which is five-jointed, is rusty brown and downy; the wings are much longer than the body, iridescent, prettily variegated with brown, leaving two transparent spots on the costal edge, and five large irregular ones on the inferior margin. The female is larger and darker, especially the thorax, abdomen, and the brown markings on the wings." - Gard. Chron.

The blisters are most prevalent in September and October, and are occasionally found on those of the Alexander and Parsnep.