36 



SCIENCE-GOSSIP. 



Tlie ab. valezina of Argyiuiis paphia is another 

 example of female dimorphism. In England this 

 form is chiefly confined to the New Forest, in Hamp- 

 shire, but in Switzerland and Germany it is not 

 uncommon. What in Argynnis paphia is an 

 aberrant form, is the normal condition of the 

 female in some species of Argyniiis. In A. sagana 

 for instance, the wings are always of a dark greenish 

 brown, with white markings ; while the male is very 

 similar on the upper side to A. paphia. The female 

 of .^. sagana bears a strong superficial resemblance to 

 an Apatura, and this arrangement of pattern may 

 possibly be in obedience to that protective law of 

 nature, which is so marked in the mimetic dimor- 

 phism, in the females of many tropical species. 



In Hypolimnas misippits, which is a Palaearctic 

 species, the female is totally unlike the male, 

 mimicking (as its name implies) the appearance of a 

 Daimis, the members of which genus are distasteful 

 to birds. 



I will say nothing further here of protective 

 mimicry and coloration, as this subject has been 

 treated frequently of late in popular works, but I will 

 pass on to the consideration of structure and anatomy 

 of Butterflies, as we shall necessarily have to 

 refer constantly to these in the following articles. 



External Structure. 



A butterfly in its structure follows the general rule 

 of the sub-kingdom to w^hich it belongs, Arthropoda 

 or Entomoida. The skeletal parts are external, and 

 are named exoskeletal. The viscera, vascular and 

 nervous systems, as well as the muscles, are internal 

 to these. The wings, which are the most conspicuous 

 parts of a butterfly, are in reality but appendages to 

 the exoskeleton, and are in themselves, when in a 

 fully-developed state, extra-vascular and devoid of 

 sensation ; though it is probable that the nervures of 

 the wings at first act as blood vessels, and afterwards 

 when the wings are dry perform the functions of 

 respirator)' tubes. 



The body of a butterfly like that of othei insects, is 

 divided in segments or somites, and consists of the 

 following primary parts — 



(a). The Head. 



The head theoretically consists of three segments, 

 containing the palpi (a) the proboscis or haustellum, 

 (h) a long spiral tongue for sucking hone)' or other 

 liquids on which the perfect insect feeds. This is 

 sometimes of great length, but when not in use is 

 curled up spirally on the under surface of the head. 

 It really consists of equal halves, joined in the middle. 



The eyes (c) placed one on either side of the head. 

 They are proporlionatel)- large globular bodies, im- 

 movable, but containing a number of separate and 

 distinct optical organs, each having its own 

 lens and nerve supply. This kind of eye is that 

 which is known as compound. 



The antennae (rf), are very important organs in all 

 insects, and are well developed in butterflies. They 

 consist of two parts, the shaft (d' ) and club (d"). 

 They are the organs of touch, and perhaps of special 



senses equivalent to smelling and hearing. The 

 extent of their functions is but little understood, and 

 most probably varies in different orders of insects. In 

 some of the social Hymenoptera they are evidently 

 used for comnuinicating intelligence from one indi- 

 vidual to another. 



The antennae are always clubbed in butterflies, and 

 this feature forms one of the zoological characters 

 of the group : from which indeed it receives its name 

 of Rhopalocera or " club-horned." The club is 

 generally ov(jid in shape, but in some genera it is 

 somewhat c)'lindrical or resembles an inverted cone. 

 In many Hesperidae it terminates in a hook-like 

 process. 



(b). Thorax. 



The thorax consists of three segments, viz., pro- 

 thorax («), mesothorax (/'), metathorax (c). On the 

 thorax are placed the organs of locomotion, a pair of 

 legs being attached to each segment (E). The legs 

 consist of femur or thigh (a), tibia (li), tarsus 

 containing three joints (c) and claws (d). Sometimes 

 the tibia is armed with spines near to its articulation 

 with the tarsus. In some families of butterflies, as 

 Apaturidae, Nymphalidae and Satyridae, the anterior 

 pair of legs are often imperfect in their structure ; 

 especiall)' those of the males. 



The wings. Which are shown on the left hand of the 

 diagram, consist of two paiis, fore-wings and hind- 

 wings, sometimes called anterior and posterior wings. 

 They are attached to the meso- and meta-thorax 

 respective!)'. They are always more or less triangular 

 in shape, and their margins are named as in the 

 accompanying figure. The base is at the insertion 

 with the thorax, the front margin is called the casta, 

 the other two margins are called outer and inner, 

 though some writers speak of the outer margin as the 

 hind margin. The point of junction of these two 

 margins is known as the anal angle. Sometimes the 

 wings are more rounded as regards outline, than those 

 in the figure, and often more indented or angulated. 



In the genus Papilio the outer margin of the hind- 

 wings is prolonged at the point d" into a tail-like 

 appendage. In many of the Lycaenidae the hind-wings 

 develop one, or even two, very small tails on the 

 outer margin. In Chara.xes there are two well- 

 marked prolongations of this kind on the hind wings. 

 In the genus Seriiimis, the tails of the hind-wings 

 are greatly elongated, so as to produce a striking 

 effect. The object of these additions to the ordinary 

 structure of the wings does not appear to admit of 

 any explanation. 



The wings of butterflies are of a membranous 

 character, formed of chitinous substance, of the same 

 material as the exoskeleton, supported by ribs or 

 ' ' bones " of the same substance. These last have 

 received the name of nervures, though they are not in 

 any way connected with nerve substance. Their 

 arrangement is well defined, and is of extreme 

 importance in classification. The nervures are named 

 as follows — (a) The costal nerviire, running from 

 the base of the wing into the costa. This as will be 

 seen in the figure is very short in the fore-wing, and 



