81 
the tumours called warbles. The fly is provided with an ovi-positor, by 
means of which it bores holes through the skin, in each of which it deposits 
one egg. The eggs develop into bots, which may be recognised by the 
growth of little elevations or tumours, called warbles. The tail end of the 
bot places itself in the tumour of the host, in order that it may. be enabled to: 
- breathe. The bot, when completely developed, escapes and buries itself in. 
the ground, and then passes through the chrysalis stage, in which it remains 
about six weeks, at the end of which time it at length emerges as a perfect 
fly, which again deposits eggs, and so the cycle goes on again. The eggs of = 
the bot-fly of the sheep are deposited in the nostrils, to the great distress of 
the poor animal. The larvee or bots pass upwards towards the sinuses or 
cavities of the forehead of the-sheep, and thus cause great‘ distress. 
ASCARIS LUMBRICOIDES, 
A, Female Ascaris Lumbricoides. B, Anterior extremity enlarged, seen from the side. 
C, The same, seen from the front, showing the opening in the centre. 
‘E, The Posterior extremity enlarged. D, Male Ascaris, natural size. 
G 
