A SYNOPSIS OF AUSTRALIAN ACARINA — RAINBOW. H7 



. Upon the question of natural enemies, Banks points out that 

 most mites have few enemies beyond their predatory relativ'es^ 

 but, " there are, however, various cases of protective resemblance, 

 especially among the immature forms. No examples of mimicry, 

 I think, are known." 



The Acarina is a very extensive order of the class Arachnida, 

 and many of the species comprising it are remarkable for their 

 minuteness and diversity of form, as well as their marvellous life- 

 liistories. A great number of the parasitic species have become, 

 as some writers have shown, distinctly modified in organisation ; 

 and owing to this, and the fact that their affinities with the^ 

 typical Arachnida are so masked by degeneration, it has been 

 urged that it would be more convenient and natural to assign 

 them to an order by themselves. Against this, it is contended 

 that most of the free-living (non-parasitic) species have departed 

 least from the typical Arachnid form, and that they display many 

 affinities to the .Solpugids and Phalangitis. The majority of 

 Aracologists, therefore, regard this group as a branch of the tru;^ 

 Arachnida. 



It is difficult to draw up a table of characters sufficiently 

 comprehensive to include the whole group, but the following 

 summary inay be of service : 



(Jephalothorax and J.6r/o»ie?i. -These segments are united, the 

 fusion being so complete that in many species they are welded into 

 one mass ; in some forms however, they are distinct. The body 

 is often provided with hairs and bristles. 



Eyes. — -Often wanting. When present the}' are simple ; there 

 are usually two pairs, each of which are placed close to the outer 

 angle ; more rarely there is only a median pair. 



Mouth. — Adapted for sucking ; mandibles partially united, and 

 form with a plate (epistonip) and the labium a beak, known as 

 the rostrum or capitulum, the latter often separated from the 

 cephalothorax by a membranous joint ; mandibles formed for 

 piercing, sometimes provided with a pair of " nippers " at the tip, 

 and sometimes simply pointed. 



/^f_(/.s.— Commonly eight in the adult form, and six in the 

 larval. The Eriophyidie, however, are uiiique in that, there are 

 never more than four in either adult or larva. In Pteroptus, 

 Dufour (Gamassidte), there are eight, both in larva and adult. 

 The legs aVe arranged in pairs, two of which are seated well 

 forward, and two behind ; the latter apparently arise from the 

 abdomen, but as Banks remarks, this is probably not the case ; 

 it is " rather that the coalescence of the abdomen and cephalo- 



