3*8 MINUTES Auo, 



124, begins to defcribe a fcgment of a circle, bring- 

 TENTHREDO ing it round with a fweep until it almoft reaches 

 the margin of the leaf on the oppofite fide of 

 the orifice ; and thus, cleaving the leaf, forms 

 a purfe-like nidus within it. 



This creates a work of confiderable labour, 

 in executing which {he employs her four in* 

 flruments with a {kill and dexterity which is 

 delightful to look on, but difficult to defcribe. 

 The two in front {he makes ufe of as hand- 

 faws ; while the two hinder ones are employed 

 as fprings to impel them forward, and make 

 them lay hold of the work* What feems to 

 make the operation go on fmoothly and plea- 

 fantly to the eye, and with apparent cafe to 

 the animal, is, the manner in which {he works 

 her front inftruments ; which are not drawn 

 up and pumed down together, but alternately, 

 and feparately, one of them rifing while the 

 other is preffed downward ; as is evidently 

 feen by their wrinkles or ferratures ; efpecially 

 if viewed through a delicate tranfparent leaf, 

 held between a good glafs and a ftrong light, 

 The nidus being formed, the fly lets her 

 inftruments recede towards its center, where 

 they remain motionlefs until the time of labour 

 Carries op; which is generally many feconds, 



often 



