CANTO iv. OF GOOD AND EVIL. 131 



i 



Who with bright lamp alarms the midnight hour, 

 Climbs the green stem, and slays the sleeping flower. 



" Fell Oestrus buries in her rapid course 

 Her countless brood in stag, or bull, or horse; 30 



Whose hungry larva eats its living way, 

 Hatch'd by the warmth, and issues into day. 

 The wing'd Ichneumon for her embryon young 

 Gores with sharp horn the caterpillar throng. 



Fell Oestrus buries, 1.29. The gadfly, bot-fly, or sheep-fly: the larva 

 lives in the bodies of cattle throughout the whole winter; it is ex- 

 tracted from their backs by an African bird called Buphaga. Adher- 

 ing to the anus it artfully introduces itself into the intestines of 

 horses, and becomes so numerous in their stomachs, as sometimes to 

 destroy them; it climbs into the nostrils of sheep and calves, and pro- 

 ducing a nest of young in a transparent hydatide in the frontal sinus, 

 occasions the vertigo or turn of those animals. In Lapland it so 

 attacks the rein deer that the natives annually travel with the herds 

 from the woods to the mountains. Lin. Syst. Nat. 



The wing'd Ichneumon, 1. 33. Linneu* describes seventy-seven species 

 of the ichneumon fly, some of which have a sting as long and some 

 twice as long as their bodies. Many of them insert their eggs into 

 various caterpillars, which when they are hatched seem for a time to 

 prey on the reservoir of silk in the backs of those animals designed 

 for their own use to spin a cord to support them, or a bag to contain 

 them, while they change from their larva form to a butterfly; as I 

 have seen in above fifty cabbage-caterpillars. The ichneumon larva 

 then makes its way out of the caterpillar, and spins itself a small 



