54 Belladonna Leaf-Mine)' 



with three apertures clearly delimited, of which tlie two placed more 

 dorsally are about half as far apart as the median and ventral. 



There would appear to be much individual variation both in the 

 size and structure of the mature larva. For instance Farsky (p. Ill) 

 states the size to be 7 mm. long and \1 mm. thick, and Professor Car- 

 penter (p. 290) gives the length as being 8-10 mm. The latter also 

 states that the prothoracic spiracles have eight to ten branches whereas 

 I have only been able to observe eight in the full grown larvae. A 

 possible explanation of such variations as being an expression of differ- 

 ences in the nature of the host plants, readily presents itself to our minds, 

 and while Farsky's larvae were reared from beet leaves and Carpenter's 

 from the leaves of mangolds, mine fed on the leaves of belladonna. 

 It may be that we get distinct " biologic species " of flies according to 

 the food plants which they patronise. 



In a note which I have from Professor Carpenter, dated October 12th, 

 1912, the writer realises the probability of variation in definite species 

 of dipterous maggots, but states also an interesting case of convergence 

 where, if one takes a large series of larvae of Lucilia Caesar and Calli- 

 fhora erythrocephola, distinctions which apparently hold good amongst 

 a small number lose their value. His attention was drawn to this fact 

 by Dr R. Stewart MacDougall. 



The puparmm (PI. I, fig. 13). 



Puparium measures 4 "8-5 mm. in length, greatest breadth about 

 1"4-1'5 mm. Shape rectangular oval, narrowing sharply both ante- 

 riorly and posteriorly, sides slightly sinuate in outline, but not so 

 markedly as in the puparium of P. hicolor (fig. 14). The rounded contour 

 of the last segment interrupted by the slightly projecting posterior 

 spiracles. Anterior spiracles less prominent with a lateral outward 

 inclination. Scarcely a trace of the posterior tubercles of the larva. 

 Segments distinct, demarcated by narrow striate bands of lineally and 

 serially arranged spines, characteristic of the larval cuticle, as shown 

 in the figure. The whole puparium as if lightly scarred or wrinkled, 

 a conditi(m due to the general contraction that occurred in the trans- 

 formaticju from the larva. Colour at first pale ochreous yellow, giadually 

 deepening through shades of red, reddish-brown to dark brown and 

 brownish-black. 



