THE SHEEP NASAL AND BEET OR MANGOLD FLIES 53 



On hatching from the egg, or on deposition, the larvae com- 

 mence to make their way up the nasal cavities, using the 

 " mouth hooks," the anal papillae, and ventral spines. At first 

 the larvae are a dirty white colour and about one millimetre in 

 length, later they change to a lightish-brown with brownish trans- 

 verse bands. 



Most of the larvae remain in the nasal fossae, but cases are on 

 record of their having been found in the nasal sinus, maxillary 

 sinus, cores of the horns, and even in the cranial cavity. When 

 mature, the larvae in the nasal fossae by causing violent fits of 

 sneezing are got rid of by the sheep. Falling to the ground they 

 pupate under clods of earth or in the ground, the flies making 

 their appearance in from 25 to 35 days. 



PREVENTIVE MEASURES. 



During June, July and August, sheep should not be allowed 

 in meadows known to be subject to the fly, but during these 

 months removed to pastures where considerable shelter from 

 the sun is to be had. The flies avoid the shade always, preferring 

 the bright, hot sunshine. 



The treatment of the nose of the sheepjis the next most 

 important point, in order to deter the fly from depositing her 

 eggs or larvae there. This can most conveniently and inexpen- 

 sively be carried out, by placing in the field wooden boxes with 

 the sides and lids perforated by holes and containing lumps of 

 rock salt ; the whole of the boxes to be externally thickly smeared 

 with tar. In their endeavours to obtain the salt the sheep 

 tar their noses. 



All infected sheep should be placed in pens and isolated, 

 in order that the larvae, when expelled, may be killed. 



THE BEET OR MANGOLD FLY. 



Pegomyia betae, Curtis. 



From all parts of Staffordshire complaints have been received 

 of the damage done by the larvae of this fly. In many cases the 

 growth was considerably checked and the yield much under the 

 average. 



LIFE-HISTORY. 



The flies appear towards the end of March or early in April, 

 and the female deposits her eggs late in May or early in June in 

 small patches on the under-side of the leaves. The larvae hatch 

 out in about a week, and bore their way into the leaf, destroying 

 the tissues between the upper and under epidermis. Very often 

 when young plants are attacked the leaves quickly take on a 

 mottled appearance and soon wither and die. The larvae are 

 about one-third of an inch long, legless, with a bluntly-ending 

 tail and tapering head, the latter being provided with two black 

 mouth-hooks. In colour they are whitish, but often appear 



