470 JOURNAL, BOMBAY NATURAL BIST. SOCIETY, Vol. XXV. 



the dark as to how the transition from an aquatic to a life in the air is 

 effected. 



The respiratory systems of the larva and imago respectively have 

 already been discussed but a few additional facts need to be added to 

 those descriptions. It has been noted that great changes in the system 

 of respiration occur at metamorphosis and that the rectal or caudal gills of 

 the larva are exchanged for the spiracles of the imago. If the larva be 

 closely examined, it will be found to possess spiracles much the same as the 

 images but smaller, less developed and quite functionless. 



The spiracles of the imago consist of two sets, one of which is situated 

 on the thorax and the other on the abdomen. On the thorax two pairs of 

 large spiracles are found, an anterior pair on the mesothorax which are 

 largely concealed by the overlapping of the head and prothorax, and a 

 posterior pair which have already been noticed on the sides of the meta- 

 thorax. The abdominal spiracles are microscopic in character and therefore 

 difficult to see. They will be found on the anterior part of the pleural 

 membrane of the first eight abdominal segments and gradually increase iu 

 size from before back, that on the 8th segment being by far the largest. 

 Immediately upon metamorphosis, the rectal gills become functionless, 

 the caudal gills are shed and the spiracular system of the larva becomes the 

 highly developed system of the imago. There is strong evidence to show 

 that thelarvaj of dragonHies once lived a terrestrial existence but that with 

 the adoption of an aquatic life, the spiracular system of respiration became 

 temporarily suppressed. 



The food of dragonflies both iu the larval and imaginal states consists of 

 insects. The former whilst young, live principally on the larvee of mosqui- 

 toes and other small water larvte : the adult larvie will however attack tish 

 and are not averse to making a meal off one of their own kind. If a 

 number of these insects be kept in a jar of water together, they will 

 invariably live one on the other. Apparently sluggish in habits, they can 

 on occasion show remarkable activitj'' and what they lack of the latter is 

 amply compensated by their cunning. The perfect insect as a rule is a sun- 

 loving creature but a few species of night-fljdng Dragonflies are found iu 

 India although they are rarely seen and more rarely caught. This is 

 because they have but a very short time of flight, generally not longer 

 than about twenty minutes, at or a little after dusk and again at dawn. 

 The food of these species is apparently entirely limited to mosquitoes. 



(Note. — I once noticed one of these night-flying mosquitoes hawking for 

 mosquitoes in the darkened corridor of a government oflice during the 

 day-time and on other occasions I have seen them flying in the day- 

 time, usually on cloudy or dull days, in the depths of wells.) 



One particular species, common enough in the Deccan, has a flight of 

 about one hovir daily, from about seven to eight in the evening. A few 

 species inhabit dark jungles and never come out in the sun, whilst others 

 will never fly except on bright sunny days. The males are more usually 

 taken in the neighbourhood of water where they are awaiting the females, 

 the latter being usually taken in scrub or jungle some distance from water. 

 This of course is not universally ai^plicable but it is a general rule and 

 serves to explain why the females are generally so much more rare than the 

 males. 



Ty^OTE ON THE PRESERVATION OF COLOURS IN 

 DRAGONFLIES. 



One of the great drawbacks of collecting Dragonflies in this country is 

 the alarming rate with which they undergo decomposition, losing as a 

 result their brilliant colouration and often dropping to pieces or shedding 



