THE BUTTERFLY OF THE OAK 



917 



butterfly makes its appearance in July, cf fluid is discharged from the butterfly's 

 The pupal skin breaks open at the destined body, and the insect then remains hang- 

 moment, the captive creeps forth, and ing. quite motionless, until the wings attain 

 immediately ascends a neighbouring twig their normal consistency and firmness, 

 or grass blade — it matters not so long as The Purple Hairstreak Butterfly is then 

 the insect can secure a firm hold for its complete. It usually climbs to a point 



feet and a clear di'op for its rapidly 

 developing wings. 



It is a fact that \\hen the butterfly 

 emerges from the chrysalis skin its every 

 part is perfect, with the form 

 and size of maturity, except 

 the pad-like wings and the 

 swollen and elongated abdo- 

 men wherein is contained the 

 fluid which will ultimately 

 flow into the wings. As soon 

 as the butterfl}' has found a 

 suitable spot, the afflux of 

 this fluid causes the wings to 

 grow very rapidl3' — so rapidly 

 that in from five to ten 

 minutes they attain their full 

 size, although they are still 

 wet. soft, and quite unfit for 

 flight. An hour or more must 

 elapse ere they become dry 

 and firm. 



The rapid development of 

 the newly emerged butter- 

 fly's wdngs is a marvellous 

 spectacle, and calls for a word of explana- 

 tion. It is brought about, as we have 

 seen, by an afflux of fluid which is driven, 

 chiefly by contraction of the abdominal 

 muscles, from the body into the wings. 

 The reader must know that the butter- 

 fly's wing is composed of two skins, 

 or membranes, lying close together 

 and supported by the veins. In the 

 newly emerged insect the two membranes 

 of the wing are corrugated — that is, 

 each membrane is, so to speak, folded 

 upon itself like a closed concertina. 

 Thus, each wing is hterally a bag 

 which, as the fluid is forced into it 

 from the body, would tend to ex- 

 pand like a balloon were it not that 

 the membranes are held closely together 

 by minute fibres or ligaments. As 

 socjn as the wings have dropped and 

 expanded to their full size, the overplus 



THECLA QUERCUS 

 CATERPILLAR ABOUT 

 TO CHANGE TO PUPA 

 (MAGNIFIED). 



of vantage, opens and closes its wings 

 once or twice as if to test them, and then 

 soars away into the sunshine. It delights 

 to froUc with its companions in woodland 

 glades and around the oak 

 trees, often ascending to the 

 topmost branches. It has a 

 habit of selecting a special 

 leaf as a point of vantage, to 

 which, if disturbed, it will 

 return time after time. In 

 this respect it resembles 

 the famous Purple Emperor 

 {Apatiira iris), wliich also 

 selects a throne among the 

 oak leaves. But although 

 this regal butterfly in its 

 perfect state is associated 

 with the oak. its caterpillar 

 must be looked for upon 

 goat -willow or sallow bushes. 

 The Purple Hairstreak 

 Butterfly has a wide range. 

 It is common throughout 

 Europe, except in the extreme 

 north and south, while it is also found 

 in Asia Minor. But in Europe Tkecla 

 quercus shares its distinction as the Butter- 

 fly of the Oak with another species, viz. 

 Thecla ilicis. As its name implies, the 

 latter insect is especially associated with 

 the evergreen oak [Quercus ilex) ; but the 

 larva — which is pale green marked with 

 yellow spots and lines — feeds also upon 

 the leaves of Quercus robur. This but- 

 terfly^ is dark brown. The anal angle 

 of the hind-wings is marked with a small 

 orange spot in both sexes ; while the 

 female has a large, dull orange blotch 

 on each fore-wing. Thecla ilicis is found 

 throughout Central and Southern Europe. 

 North Africa and Western Asia. It 

 abounds in every oak wood in Germany 

 from May to July. That it does not 

 range into England is a fact difficult to 

 explain. 



