DIPTEEA OR TRUE FLIES. 251 



lower epidermis, thus clearing out the green mass of the leaf 

 and leaving behind a pale blistered patch. The grubs are the 

 larvae of the so-called Celery Fly, which is a small pale-brown 

 ily, with wings mottled with dark brown, and with green eyes. 

 It lays its eggs on the celery leaf, and the young larvae at once 

 burrow into the interior. They are found hovering over the 

 celery plants as early as Apri), but the majority come out in 

 June. The pale blisters become brown, and inside these 

 diseased spots the white larva may turn to a yellowish 

 puparium. There are several generations in the year. Some 

 puparia are found in the earth, especially during the winter 

 months. The larvte go on working in mild winters as long 

 as the celery is in the ground. They must not be confused 

 with the Celery-stem Maggot, Piophila apii, although the A. 

 heradei larva has been found in the celery stalks. 



Prevention and Remedies. — As we find the puparia in the 

 leaves and in the ground, we must try to get rid of them 

 in both places, and so effectually stop their increase. The 

 leaves should be burnt and the beds dressed with gas-lime 

 in the winter, as after all attacks of garden pests. Spraying 

 the young celery plants with tobacco wash, every now and 

 then in the summer, keeps oif the fly. The old plan of 

 pinching the leaves that are blighted cannot be advised, as 

 the leaves get ruptured and the sap pours out, and thus more 

 damage is done than by the larva. 



Young celery before being set out should be kept in bright 

 weather covered with muslin, so as to stop the flies from 

 laying their eggs. 



Family MUSCID.S. 



The House-fly (Musca dombstica). 



Although the House-fly is not an agricultural pest, yet it is 

 sufficiently obnoxious to allow a few lines to be devoted to it. 

 The House-fly {M. domestica) belongs to the family Muscidse, 



