Microscopical Essays, 229 



the tail. This may be feen by expofmg the pupa a little while 

 to the rays of the fun, and then putting it's tail in water, when 

 you will find it breathe ftronger than it did before, and, by ex- 

 preffing an air-bubble out of it's tail, and then fucking it in again, 

 will manifeftly perform the aclion of infpiration and exfpiration. 

 The anterior part of the pupa is drawn back from the fkin, and 

 having partly deferted it, the beak, head, and firft ring of the 

 breaft, the little creature lies Hill, until it's exhaling members 

 have acquired ftrength to burft the two membranes which 

 furround it. 



If the exterior cafe is opened near .this period, a wonderful 

 variety of colour may be perceived through the thin fkin which 

 inverts the pupa. The colours of many of the different parts are 

 now changed; fome parts from aqueous become membranaceous, 

 fome flefhy, and others cruftaceous. The whole body becomes in- 

 fenfibly fhaggy, the feet and claws begin to move : the variations 

 may be accurately obferved by opening a pupa every day until 

 the time of change. For this purpofe they mould be laid on 

 white paper, in an earthen dim f they mould alfo be made fome- 

 what moift, and be kept under a glafs : the paper ferves the pupa 

 to fix it's claw to, when they come forth in the form of a fly. A 

 little water mould be poured into the difh, to keep the pupa from 

 drying and fuffocation. 



When the fly begins to appear, the exterior (kin is feen to 

 move about the third and fourth anterior ring ; the infect then 

 ufes all it's efforts to promote it's efcape, and to quit the interior 

 and exterior fkin at one and the fame time. The exterior fkin is 

 divided into four parts ; the infect immediately afterwards breaks 

 ~ open 



