XIX] 



AND BIOLOGICAL METHODS 



359 



At the fourth or fifth instar they should be transferred to larger "observation 

 jars," and fed on water-fleas, or small mosquito-larvae. Only one species of 

 larva should be kept in each jar. Later on they may be fed with larger 

 mosquito-larvae, or small Agrionid larvae. 



Glass cells, either rectangular or cylindrical, make excellent observation 

 jars (fig. 187). These should have a clean sandy bottom, with water-weeds 

 growing thevein. I find Vallisneria and Elodea the best forms for aerating the 

 water, particularly the former. The duck-weed (Lemnd) and the pretty 

 Azolla are also invaluable as surface weeds. A few sticks should be arranged 

 so as to stand up some inches above water-level, for the larvae to climb up 

 at metamorphosis. 



For bottom-dwelling larvae I use a small circular tin pan (fig. 188), with 



Fig. 187. Observation jar for 

 rearing dragonfly-larvae ( x J). 

 Original drawing by P.' 

 Tfflvard. 



Fig. 188. Pan for rearing rock or bottom - 

 dwelling larvae ( x f ). Original drawing by 

 P. TiUyard. 



sloping sides about three or four inches deep (a puppy's drinking pan is a 

 useful kind). A sandy bottom, a small piece of rock or two, and a liberal 

 supply of Lemna for the aeration of the water, are all that is required. 



When the larvae are full-fed, a small cage, open below, and constructed 

 of mosquito- netting on a wire framework, should be let down over the 

 observation jar or pan. The larvae will crawl out up one of the sticks or on 

 to the netting, and the imago will be found resting at the top of the cage. 

 It may then be removed to a larger cage of similar design, to allow the wings 

 and colours to mature. Bred specimens, however, are seldom at all satisfactory 

 for the cabinet, as maturity depends not only on time and sunlight, but also 

 on activity and feeding. Captive imagines, as far as my experience goes, 

 cannot be persuaded to feed. I find it convenient to place all bred specimens, 



