290 Dr. T. A. Chapman's Contribution to 



icarus and thersites, not close to the orange spot as in medon. 

 The underside is definitely thersites. Curiously enough, of 

 a pair of what are almost certainly thersites (appendages 

 not examined) from Hungary in the collection of the 

 Hon. N. C. Rothschild, the $ has these black kernels dis- 

 posed very much in the fashion of medon, in neither speci- 

 men is there any trace of blue scales, that are never present 

 in medon, frequent in the other two species. 



In captivity (at Le Lautaret and Bourg d'Oisans) the 

 butterflies laid eggs freely on Sainfoin. It was necessary 

 as with practically all these blues to place the plant on the 

 bottom of the cage, when they appeared to lay wilhngly 

 on the leaflets, especially the undersides, visiting very 

 sparingly upright leaves and stems, rarely laying on the 

 calyces, never (or hardly ever) on the corollas. P. icarus 

 is perhaps the least unwilling of the species I know, in 

 this regard, to lay on leaves and flowers at some height. 



The eggs of A. thersites are of the usual Plebeiid type, 

 Hke those of P. icarus as belonging to this type, but difl^ering 

 in several definite respects. It is hardly appreciably 

 smaller. One marked difference is in the size of the 

 individual cells of the adventitious coat, which are a third 

 larger in thersites than in icarus, i. e. their diameters at 

 corresponding zones of the eggs are as 4 to 3. The columns 

 at the angles of the cells are markedly larger, higher, and 

 bolder in thersites than in icarus. The micropylar area is 

 much larger in icarus than in thersites. Both these circum- 

 stances are well shown in the photograph of the eggs 

 (PI. XXXV). The structure of the micropylar area is 

 affected in even a larger degree than the rest of the egg, 

 in having the cells larger and fewer, as is evident in PI. 

 XXXVI. I present photographs of two specimens of 

 each species, showing that the difference is not an individual 

 variation. 



I present most of the following notes on the larvae 

 roughly, as entered at the time. On various points I trust 

 to plates rather than to lengthy description. 



Sept. 2. Some thersites hatching onwards from 8th 

 August are now in their third skins, some from eggs laid 

 about August 18th and hatching 26th to 27th are still in 

 1st instar. 



When newly hatched the larva is less than 1 mm. in length, 

 nearly colourless, a pale slaty tint, and looking semitransparent, the 



