a pane of glass is placed into a 50 -cm part of one of the walls, for 

 observation. The wheels are made of vinyl and their axis is a glass rod; 

 the current is created by 8-vaned wheels with a small motor. These wheels 

 are preferable to propellers as they create a uniform current. Each tray 

 contains 30 liters of water (Frantsev, 1961:324—325, Figure l). 



Wiggins described breeding cages of aluminum screen, covered with 

 glass; these cages are placed in wooden frames; the frame is placed on 

 a tray with running water; the frame may be placed in the river; only its 

 lower half should be in the water (Figure 180). Breeding cages may also 

 be used in stagnant water such as ponds and calm parts of lakes; the 

 buoyancy of the frame and the immersion of the breeding cages to the 

 necessary level should be ensured (Wiggins, 1959). Food and twigs for 

 the pupae to emerge should be placed in the cages. 



The serial breeding cages make simultaneous observations on several 

 species possible; one larva can be placed in each cage; several pupae can 

 be placed in a cage if it is sure that they belong to the same species. 



Full-grown larvae are identified with a binocular microscope; the 

 mandibles of the larva should be separated. For the examination of smaller 

 structures, the larva has to be dissected and examined under the microscope; 

 this is necessary for the study of the mouthparts, the chaetotaxy and the anal 

 legs. 



To identify small species, and for morphological studies, microscopic 

 preparations are made on 3 slides in the following order: l) dorsal view of 

 head, ventral view of head (the maxillolabium is not separated), dorsal view 

 of labrum, dorsal view of right and left mandible; 2) dorsal and ventral 

 thoracic sclerites; sclerite of segment 9; outer view of right anal leg, inner 

 view of left anal leg; 3) legs: left column: legs 1—3, posterior view; right 

 column: legs 1—3, anterior view. The preparations are usually made in 

 Faure's gum medium; permanent preparations are mounted in Canada 

 balsam. The sclerites can be separated from the muscles by dissection 

 under the binocular. The larva may be treated with KOH. 



The 1st and 2nd stages of the larvae are often almost transparent and can 

 be examined directly under the microscope. 



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