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71 



HUTTERFLIES Ol 



.\i..\i:.\K( I ic kicGiox. 



By IlKNRV Chaki.ks Lani;, M.D., M.K.C.S.. L.K.C.r. Lonh 



iConthtutd from pagi- 38. > 



T T is not my intention 10 <lo more than give a few 

 s»[H;rrtcial observations on the- subject of Internal 

 Anatomy. 



Nervous System. 



This in insects generally, is what is called tliplo- 

 (janyliated, that is, it consists of two double longi- 

 tudinal cords of nerve substance running along the 

 ventral or lower surface of the body. In the lower of 

 these the nerve tissue is enlarged at intervals into 

 knots or ganglia. In the larvae of Lepidoptera these 

 are distinctly separated into sometimes thirteen, or 

 even fourteen pairs. During the pupa state in butter- 

 flies, however, some of them become fused, so as to 

 form large nerve centres. The gangliated iiervous 

 system of insects is not to be considered as resembling 

 the cerebro-spinal system of vertebrates. Thus the 

 cephalic ganglion in the head which supplies the organs 

 ol sense, is not of such vital importance to the insect 

 iis the two ganglia that are situated in the thorax, and 

 distribute nerves to the orgiins of locomotion. It is 

 true, the chief nerve centres are situated in this part of 

 the body, and that a IjutterHy may be instantly killed 

 by sharp and firm pressure upon the underside of the 

 thorax. The four abdominal ganglia give out 

 branches for the supply of the digestive and reproduc- 

 tive organs. 



Vascular .System. 



This in butterflies is of a very simple character. 

 The centre of the circulation is a rudimentary heart 

 called the "dorsal vessel," situated on the dorsal 

 surface of the abdomen and divided into several 

 chambers. It is controlled by muscles attached to 

 the abdominal walls, and by their action the blood is 

 propelled into the aorta, which is a prolongation of 

 the dorsal vessel, having the form of a tube passing 

 through the thorax to the head. The blood then 

 returns through the lacunae or interspaces of the 

 various organs to the abdominal sinus which 

 surrounds the dorsal vessel and thence into the vessel 

 itself through special valvular openings. There are, 

 in insects, neither arteries, capillaries, nor veins, in 

 the true sense of the words, and the blood is cold, 

 colourless and not corpusculated. As above stated, it 

 -is usually held that in butterflies the ner\»res of the 

 wings convey the blood to those appendages, until 

 they arc fully unfolded after the emergence of the 

 insect from the pup.a. Circulation through the.se then 

 ■ceases, the texture of the wings becoming dry and non- 

 vascular. The ner\'ures then perform the functions of 

 air-tubes. 



Kl'.SI'IRATION. 



The respiratory system in butterflies consists of a 

 number of tubes called tracheae, ramifying through 

 all parts of the body ,ind communicuing with the 



external air by means of apertures in the lateral 

 regions of the integument. These apertures are 

 called spiracles. The tracheae, besides ]jcrforniing 

 the function of respiration, form a kind of cndo- 

 skelelon ami bind together the soft parts after the 

 manner of ligaments. 



Dii;f.stivk Svsiem. 

 This consists of the pharynx which is attached to the 

 organs of the mouth. It narrows into a gullet or oeso- 

 phagus, which passes through the tirst segments of the 

 body and is dilated into a stomach or crop. Posterior to 

 this is the intestine. This is situ.tted in the abdomen 

 and convoluted, and though of considerable length, it 

 is simple in character and terminates without much 

 change of stiucture at the anal orifice. 



ReI'ROIiUCIION 



takes place by means of eggs which are laid by the 

 fem.ile on suitable food plants, either singly or in 

 batches. Hutlerflies are never hatched before leaving 

 the body, as is the case in some insects. I'artheno- 

 genesis is unknown amongst butterflies, though it is 

 found occasionally in some Ilelerocera. 

 Thk Etics. 

 The ova of butterflies are very various in shape, 

 and occasionally present some striking forms. The 

 surface is sometimes smooth, but more often as it 

 were sculptured with various patterns in the shape of 

 ribs, network, flutes or stripes. The egg state is the 

 first stage of butterfly-life, and its duration varies 

 with sea-son and latitude. When the contained 

 embryo reaches its full development, it escapes from 

 the eggshell as a larva or caterpillar ; this forms the 

 second stage of existence. 



C ATKRI'II.I.ARS. 

 The lar\a may be said to contain all the essential 

 parts of a butterfly, except the wings and the fully de- 

 veloped generative organs ; but the internal anatomy 

 becomes greatly modified in subsequent stages. 

 Although butterflies in their perfect state are 

 hauslellate or sucking insects ; as larvae they are 

 furnished with mandibles or jaws for biting and 

 tearing. Beneath these are the maxillae, which are 

 soft and useless, except as prehensile organs. Other 

 organs situated in the head are the maxillary aud 

 labial palpi and a structure called a spinneret, from 

 which the silk is produced liy the larva in constructing 

 webs, as in the case of the black-veined white 

 butterfly Aporiaitatacgi, or in the construction of the 

 girths or integuments of silk which are required on 

 entering on the pupa state, .-\round the mouth are 

 arranged the simple eyes or ocelli, usually to the 

 number of six, which form the organ of vision in the 

 larval state. Posteriorly to the head the body of the 

 larva consists of twelve segments. The three 



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