400 THE PHILOSOPHY 



each day, which is a daily confumption of 480 caterpillars. 

 This fum, nvultiplled by 7, or the days of the week, gives 

 8360 caterpillars extirpated weekly from a garden. The 

 utility of thefe birds is not limited to this circumftance 

 alone ; for they likewife feed their young with butterflies, 

 and other winged infe£l5, each of which, if not deftroyed in 

 this manner, would be the parent of feveral hundreds of cater-' 

 pillars. Thofe butterflies and caterpillars which are covered 

 with hair are rejected by fome birds, who prefer flies of a 

 fmoother and fmaller kind. But thefe hairy fpecies, it 

 fliould be coniidered, are the food of the worms which are 

 transformed into thofe fmaller flies that afford nourifhment 

 to the birds which reject the hairy caterpillars and butter-? 

 flies. 



Shell-fifhes are extremely prolific, and fo flrongly fortified 

 by Nature, that their increafe, one ihould imagine, would 

 foon augment to a degree that might be hurtful to other 

 fpecies. Their noxious multiplication, however, is checked 

 by numberlefs enemies. But their mofl defl:ru6tive enemy 

 is the trochus, which is a kind of a fea-fnail. This animal is 

 furnifhed with a ftrong, mufcular, hollow trunk, bordered at 

 the extremity with a cartilage toothed like a faw. Againft 

 this inilrument, which a6ls like an augre, no fliell, however, 

 hard or thick, is a fufHcient defence. Thefe animals, called 

 trochi, fix thomfelves upon an oyfler or a mufcle, bore through 

 the fhell with theirtrunk,anddevourtheirpreyat theirleifure. 

 The animal attacked, if a bivalve, may open or fhut its fhell ; 

 bat no efforts of this kind can be of any avail ; for the tro- 

 chus remains immoveably fixed till it has completely fucked 

 out the vitals of its prey. In this cruel occupation the tro- 

 chus often continues for days, and even weeks, before the 

 life of the animal attacked is fully extinguifhed. The ope- 

 ration of the trochus may be feen in the fhells of many oyf- 

 ters, mufcles, and other fhell-fifhes ; for their ihells are often 

 pierced with a number of circular holes. 



