ilG 
DIPTERA. 
tar is so offensive to insects that they cannot endure 
soil impregnated with its odour 
Bot-Fly {^EstriLS bocis ) magnified. 
The family of JEstridce contains those insects which, in 
their larval state, are well known under the name of Bots , 
Wurmah , etc. These insects (JE. bovis ) deposit their 
eggs on cattle, in whose bodies the larvae are nourished. 
The presence of the fly is soon felt amongst the herd of 
cattle ; with tails turned upon their backs or stretched 
stiffly out in the direction of the spine, off they gallop 
about their pastures in the wildest state of terror. An 
allied fly (.JEstrus ovis ) (Fig. 13), infests sheep, laying 
its eggs within the nostrils, from whence the maggots 
make their way into the head, feeding on the mucilage 
produced in the maxillary and frontal sinuses. When 
ready to assume the pupa stage they fall to the ground 
