226 



similar nature which have been recorded are briefly 

 summarised in the paper referred to. 



Whilst such examples of insects parasitic in the 

 breathing system of insects are not uncommon, the case 

 of an Acarine truly parasitic within the insect respiratory 

 system, such as is found in Tarsonemus woodi, is the 

 only instance on record. The reported casual occur- 

 rences of other mites in the respiratory system of the 

 hive bee are not examples of parasitism and are of no 

 direct importance in relation to acarine disease. 



The Thorax of the Bee — the region of occupation by 

 Tarsonemus woodi. 



It can be readily seen that in the early stages of 

 development the thorax of a bee is made up of three 

 segments. In the adult body the limits of these 

 divisions are very much obscured, although by careful 

 dissecting, the several parts of the external covering 

 pertaining to each can be distinguished. These three 

 regions are appropriately known as the pro- meso- and 

 meta-thorax. Internally there passes through the 

 thorax on the under-side, the nerve chain upon which 

 occur the ganglia of the thorax, while dorsally the 

 tubular heart passes through the same region. The 

 great mass of tissue within the thorax consists of the 

 muscles for flight and for movements of the wing other 

 than flying. There are three unpaired and two paired 

 air sacs constituting part of the thoracic breathing 

 system, and various tracheal tubes supply those muscles' 

 and nerves as well as the structures within the head and 

 limbs. 



Our immediate concern in acarine disease is with the 

 thoracic segments and the organs they support. Ex- 

 ternally the anterior segment consists ventrally in the 

 adult bee of a number of movable pieces of hard 

 chitin connected by a softer membrane. These ventral 

 portions are readily detachable on removal of the first 

 pair of legs, and if the division is effected by a sharp 

 instrument, it is usual for them to be carried away 

 along with the legs. The dorsal and side pieces are 

 connected to form a slender hoop-like part, not very 

 broad on the back, and tapering ventrally down each 



