THE RAT-TAILED MAGGOT. 619 



been impressed with the wonderful power and foresight dis- 

 played in this one point. Suppose that an Eristalis larva, or 

 Rat-tailed Maggot as it is popularly called, be put into spirits 

 of wine for the purpose of killing it, the tail at once contracts, 

 so that no one who was not acquainted with the creature could 

 recognise it. If, however, the tip of the tail be seized between 

 the points of the forceps, and the organ be drawn out to its full 

 extent, the air-tubes can be seen to unfold themselves with the 

 most perfect accuracy. A hitch never occurs, but the coils, or 

 ratlier the folds, open out one after the other, and the two 

 convoluted tubes become straight and parallel. 



This remarkable tail is rendered necessary on account of the 

 habits of the larva which owns it. The creature lives in a 

 manner which to us would be about as miserable as can be 

 imagined. It passes the whole of its life immersed in thick 

 and semi-putrid mud, with its head downwards. The mud 

 cannot be too thick, too black, or too noisome for this larva. 

 There was one place where I could procure as many Eat-tailed 

 larvse as I liked. Just under the eaves of a church roof a large 

 tub had been sunk in the ground, for the purpose of catching 

 the rain-water. Year after year it had been neglected, and it 

 had become two-thirds full of a horribly fetid mud, composed 

 of dead leaves, worms that had crawled over the edge of the 

 tub and fallen into the water, frogs and toads that had foolishly 

 jumped into the tub, forgetting that they could not jump out 

 again, quantities of moths, beetles, and other insects that had 

 inadvertently fallen into the water and been drowned, field-^ 

 mice that had overbalanced themselves in trying to drink, and 

 other substances too numerous to mention. 



The state of such a mud can easily be imagined, and yet this 

 horrible compoimd was in its way a Paradise to vast numbeis 

 of Rat-tailed Maggots, which were busily employed in their 

 beneficent task of transmuting death into life, and of devouring 

 this poisonous and mephitic mud, so that it might be changed 

 into bright and active flies. Such is indeed the task of these 

 and many other insects, and it is absolutely impossible to 

 exaggerate the debt of gratitude which we owe them. Every 

 Drone-Fly which we see is a living proof that a certain amount 

 of pestilential matter has been consumed and rendered harm- 

 less, and it is evident that such insects ought to be encoura<-ed 



