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Insecta. Arachnida. 



Body clearly divided into three Three divisions never clear in 



regions — head, thorax and adult. Head and thorax 



abdomen. often fused, c.^., spiders. 



Three pairs of walking legs. Four pairs of walking legs. 



Breathing by tracheae. Modes of breathing various — 



Tracheae, lungbooks, skin. 



Examples: — Examples: — 



Cockroaches. Spiders. 



Beetles. Scorpions. 



Bees. Mitesi e.g., Tarsonemus woodi. 



Flies. Ticks. 



Moths. 



I have endeavoured by the foregoing comparison and 

 contrast to set out the relationship between the bee 

 and its parasite, the mite Tarsonemus woodi. It is 

 desirable that this should be understood when we are 

 considering the features of the disease resulting from the 

 invasion of the bee by the latter. It will be understood 

 from the foregoing that as far as increase is concerned, 

 there is no parallel with a bacterial or a protozoal 

 invasion. Only one other point need be emphasised. 

 The female Tarsonemus breathes by means of a set of 

 tracheae, which derives its air supply from that within 

 the trachea of the bee. The male mite and larva breathe 

 through the delicate covering of the body, 



Acarina or Mites. 



In the simple scheme of Classification outlined above 

 I have shown the general structural resemblances and 

 differences between Insects and Mites. In these 

 "Notes" I do not propose to digress from the main theme 

 more than is immediately necessary, consequently it 

 is not my intention to write at length or with any at- 

 tempt at fulness on the subject of mites in general. 

 They constitute a group of animals which have been 

 studied seriously by only a limited number of workers 

 in the past, and to-day there are surprisingly few acaro- 

 logists of reliable repute in the whole world. Mites 



