38 [FeUruuvy, 



larva recently hatched and before the skin had stretched out, and 

 therefore smaller and photographed with a larger magnification ; that 

 of argiades is from a larva nearing its first moult. As a matter of 

 fact the size of the head and diameter of the prothoracic plate of the 

 two larvae are nearly the same. Still, in all stages minima has a 

 shorter and thicker larva, in accordance with its being an internal 

 feeder, in pods (Phaca alpina) and flower heads (AnthyUis) ; argiades 

 feeding externally in the ordinary way, is more extended and slender. 

 As differences, the dorsal hairs of argiades are longer than those of 

 minima as 0.2 mm. against 0.18 mm. on the thorax, and 0.28 mm. to 

 0.19 mm. on the abdomen. On the other hand tlie supra spiracular 

 pair of hairs (III ?) are longer in minima, the ajiterior about 0.06 mm., 

 the posterior 0.02 mm. — in argiades the anterior is about 0.016 nmi., the 

 posterior evanescent. The seventh abdominal segment has two lenticles 

 in minima, only one in argiades. The special angular hair of the pro- 

 thoracic plate is more fully developed and obvious in argiades (pi. V, 

 fig. 1). 



Comparing pi. V, fig. 2, with fig. 2, pi. XVIII, in Tutt (I.e.), it 

 appears that the hair bases and especially the lenticles, have the stellate 

 spicules more developed in argiades. PI. VI, fig. 2, shows the prolegs 

 to be very similar to those of minima. PI. VI, fig. 1 , gives the dorsal 

 surfaces almost from spiracle to spiracle of the 3rd, 4th, 5th and 6th 

 abdominal segments of the last stage larva, and shows the general 

 distribution of hairs and lenticles. 



EXPLANATION OF PLATES. 



Plate II. — Figs. 1 and 2. — Larva in penultimate instar. 



„ 3 and 4. — Larva full grown in last instar. 

 Fig. 5. — Larva in hibernating plumage. 

 „ III. -Skin of larva in first instar, X 60. 

 „ IV. — Skin of larva in last instar, X 16. 



V. — Fig. 1. — Prothoi-acic plate, first instar, X ^50. 

 „ 2. — Spiracular region, last instar, X 100. 

 „ VI. — „ 1. — Dorsal region, last instar, X 40- 

 „ 2.— Prolegs, x 100, 



Eetiila, Eeigate : 



December I'jth, 1914. 



