257 



This is desirable since it sometimes happens that a 

 part of the tracheal system has been left behind. 



The freshly mounted preparation is now ready for 

 examination. The parts of the tracheal system which 

 are liable to be occupied by the mites will be recognised 

 as transparent tubes with spirally lined interior. In 

 an infested bee the tubes may be more or less bronzed 

 or soiled, and mites will be present within. It must 

 of course be remembered that in each bee there is a 

 pair of such tubes in the thorax. It will be found that 

 as regards details beyond the main trunks, there is a 

 certain amount of individual variation in the branches, 

 but for our purpose we are not concerned with these 

 parts of the tracheal system which on account of their 

 limited dimensions cannot be occupied by the parasite. 

 Attention is also directed to the distinctive structure 

 of the initial part of the system, which must always be 

 observed if initial cases of infestation are to be recog- 

 nised. 



In making preparations by the foregoing method, it 

 will be found, as manipulative skill increases, that it is 

 best to separate out from each other by means of the 

 needles the various tissues which are found in immediate 

 proximity to the thoracic tracheae. Should the tracheae 

 be ruptured in the course of dissection, it is well to 

 examine these tissues also for any mites which, owing 

 to this, may have been liberated from the respiratory 

 tubes. The bulk of such tissues consists of the muscles 

 of flight and of the thoracic glands. 



