The methods used by Evans (1957) for the demonstration of dehydrogenase 

 activity in the digestive tract of the fly Calliphora was improved for the pur- 

 pose of this work. Fresh extirpated organs in the physiological saline for in- 

 sects were washed quickly in a phosphate buffer, carried into reaction mixture 

 composed of 0-1 M natrium succinate pH 7-4 phosphate buffer and 0-1 

 per cent triphenyltetrazolium chloride. The organs were extirpated at a low 

 temperature in a dish filled with ice the temperature being raised after the 

 evacuation. There followed one hour of incubation at 37°C under anaerobic 

 conditions. After the results Imd been read the preparations were fixed in 

 the formaline with CaCl._, added and after a control evaluation embedded into 

 glycerine jelly. 



As an object suitable for the study of qualitative changes in the activity 

 of dehydrogenases in separated organs the sawfly Cephalcia abietis L. was cho- 

 sen. At the end of the larval feeding these specimens form the diapausing pre- 

 pupal stages of eonymph and pronymph, their diapause lasting usually for 

 2 years. When the diapause is finished the pronymph pupates and pupa goes 

 through a relatively short post-diapause development. Relative changes 

 in the activity of succinic dehydrogenase in different developmental stages 

 of the sawfly are made evident on Table 1. Each date represents an average 

 of at least 5 determinations. As it can be seen in the Table the pre- and 

 postdiapause development is characterized by an intensive succinodehydro- 

 genase activity, chiefly in muscles, digestive tract, Malpighian tubes and nerve 

 system. On the other hand during diapause the activity of this enzyme 

 appears to be very low and is restricted only to the intersegmental muscula- 

 ture. At the early period of eonymphal diapause after the last larval moulting, 

 reducing activity disappears firstly from the nervous system and then from 

 the other organs. During eonymphal-pronymphal transformation, i. e. during 

 growth of the imaginai discs between eonymphal and pronymphal diapause 

 a slightly renewed succiriodehydrogenase activity could be resistered in places 

 of growing imaginai discs, namely in the brain, in gonads and between the 

 mid-hind part of the digestive tract. When diapause is finished the develop- 

 ing pro nymphs show an increased activity first in the brain, thoracic muscula- 

 ture, accessory genital glands and later also in the mid-part of the gut and in 

 the remaining musculature. During the pupal development, rapid increase of 

 succinodehydrogenase activity can be observed mainly in the wing muscu- 

 lature and in muscles in general, in the nerve system, in the digestive tract, 

 genitals, accessory genital glands and in Malpighian tubes. The method reve- 

 aled a weak activity of the fat body in growing larvae only. Malpighian tubes 

 manifested a distinct activity of succinodehydrogenase in growing larvae, at 

 the end of the pupal stage and in adults. 



The results of our experiments show that the reduction of triphenyltetrazo- 

 lium chloride is really closely connected with the changes in growth of individual 



224 



