468 JOURNAL, BOMBAY NATURAL MLST. SOCIETY, Vol. XXV. 



but should the larva be disturbed, it will at once bring into play the 

 apparatus described above. The action is somewhat of the nature of a 

 turbine, for by driving out forcibly through the valves or tube, the water 

 contained in the rectum, the larva is shot forcibly onward through the water. 

 The force of the expelled column of water is sufficient to stir up a cloud of 

 mud in the immediate rear of the insect which serves to cover its retreat 

 very much in the same way as does the squid with its inky emanations. 



The anal aixpendayes of the imago are derived from the anal appendages 

 of the larva but the origin of the inferior appendage of the Anisopteridte 

 is not analogous to that of the inferior appendages of the ZygojDterida-. 

 If the anal extremity of an Anisopterid larva be examined, it will be 

 seen to present quite a number of appendages. At the extreme end 

 and centrally placed are three pointed processes lying in close apposition 

 to each other and forming what is known as the " anal pj'ramid." These 

 are the true larval anal appendages and are represented in the Zygoptera 

 by the caudal gills. At the fifth in star, another pair of smaller appen- 

 dages make their appearance above and to the outer side of the anal 

 pyramid, whilst in the male larva a third appendage or thickening will be 

 apparent lying between these two. When metamorphosis occurs, the 

 following changes take place : — T'lie anal pyramid is entirely lost in the 

 Anisoptera while in the Zygoptera the median portion only is lost, the 

 lateral pieces becoming the inferior anal appendages of the imago. The 

 median process whose late development was commented upon, forms the 

 inferior anal appendage of the Anisoptera males. The two upper lateral 

 appendages ultimately become the superior anal appendages of both the 

 Aniso-and Zygo-pterids. 

 The Respiratory System. 



The larvte of Dragonflies possess a respirator}'- system fitted to their 

 environment and which afterwards becomes considerably modified in the 

 imago to meet the needs of a life spent in the air. The systems differ 

 in important details and so must be described separately under the two 

 main divisions. The Anisopteridpe larvse are rectal breathers that is they 

 respire through their rectal lining membrane by a system of rectal gills. 

 The valvular flaps already mentioned above, are opened and through them 

 or through the tubular structure also mentioned, water is taken into the 

 rectum and from it the contained air is extracted and passed on into the 

 air vessels. (Plate XIII.) The rectum extends for about half the length 

 the abdomen and then expands into a large sac-like structure which 

 functionates as a stomach or gizzard. On either side of the alimentary 

 tract runs a large tracheal tube which narrows rapidly as it passes the sto- 

 mach towards the rectum, to form the bronchus which ultimately breaks up 

 into minor vessels called ''bronchi," which latter after anastomosing with 

 those of the opposite side, gradually lose themselves on the end of the 

 rectum. From the main bronchus come ofi' smaller bronchial tubes which 

 pass to the rectum and there break xip into a root-like mass on its coelomic 

 surface. These tubes are given oft" throughout the whole length of the bron- 

 chus below the stomach but the larger ones come off in two large masses 

 at the level of that viscus from the lower end of the trachea and run down 

 parallel to the main bronchus before passing to the rectum. The terminals 

 of the bronchi end in small papilhe on the inner lining of the rectum which, 

 is studded with an incredible number of these minute processes. If traced 

 above, each trachea will be found to break up into smaller vessels and these 

 again into smaller which ultimately pass to the head, trunk and limbs. 



The alimentary tract and the major part of the respiratory system run up 

 in the coelomic cavity, the space between the body Avails and the viscera, 

 which is filled with a pale, green fluid, the blood of the larva. 



