THE REV. JOHN WHITE. 37 



cimens of the Sphex formicarum falco ; for it is a great pity 

 that so diverting an account as that which you give of that 

 insect should be lost to your Fauna. 



You must be sure to caution Linn, that the CEstrus curvi- 

 cauda is by no means the parent of the star-tailed water-maggot, 

 though Derham says it is ; Swam., Geoffrey, and others have 

 since discovered that wonderful maggot to be the offspring of 

 a Musca hydroleon : see Geof. ; he calls it Stratiomys. You 

 will be the means, I perceive, of correcting many mistakes, and 

 new arranging many misplaced articles in i Syst. Nat.,' which I 

 wish to see as perfect as possible. I wish you may catch a 

 curvicauda before the autumn is over : you will at once be con- 

 vinced that it is an CEstrus. Os nullum, punctis tribus, &c. : 

 it sometimes haunts upland fields, and teazes the horses at 

 plow ; but is more frequently found in swampy wet places, 

 and is probably aquatic in its larva state. The nits laid on my 

 horses at Meon-Stoke Aug 19th stick on their legs and flanks 

 still. * * * Skinner can if he pleases, send several ques- 

 tions and pertinent enquiries relative to 'Syst. Nat.,' which he 

 well understands, with its comparative merits and defects, as 

 far as the author has borrowed from or imitated Mr. Ray. 



Next summer I will, if possible, get a grass-hopper lark: 

 but they are not easily procured ; they skulk in the hedges 

 like mice. 



When you write to Linnaeus next, pray talk to him about 

 tortoises f. There are tortoises whose shells are always open 

 behind and before " apertura testae anterior," as he says him- 

 self, " pro capite et brachiis, posterior pro cauda et femoribus." 

 These apertures are supported as it were by pillars on each 

 side, and can never be closed. Of such construction is the 

 shell of Mrs. Snooke's present living tortoise, Timothy. But 

 then there are tortoises whose under shell has a cardo or hinge 

 about the middle of their bellies commanding one lid or flap for- 



t [The letter from John White to Linnaeus, which was the result of 

 this suggestion of Gilbert's, certainly gave the great Swede the first idea 

 of the two distinct families of Testudinata in question j but he failed 

 to name his brother as the real author of the observation. (See note to 

 p. 240, Vol. I.) T. B.] 



