332 Acarology 



17. Valinontia Oudemans, 1923 



Type. Valinontia niira Oudemans, 1923 



18. Viedebanttia Oudemans, 1929 — deutonymph 

 Type. Viedebanttia schniitzi Oudem'dns, 1929 



Pontoppidaniinae Oudemans, 1925 



Genera: 



1. Pontoppidania Oudemans, 1923 



Type. Tyroglyphiis littoralis Halbert, 1920 



2. Ca/vo//a Oudemans, 1911 



Type. Calvolia hagensis Oudemans, 1911 (= Tyroglyphiis heteroco- 

 mils Michael, 1913, hypopus) 



3. Diphtherogly phus l<lesbin, 1950 



Type. Diphtherogly phus maculata Nesbitt, 1950 



Discussion: 



the members of the family Acaridae are notable for the extent of their 

 distribution. They are found in all types of habitat from Arctic tundra to 

 tropical rain forests and wherever man in his wanderings has taken mites in 

 his food and produce. Living on all kinds of organic substances, these crea- 

 tures are commonly found infesting such materials as preserved meats, 

 cured and raw hides, organic powders, seeds, and farinaceous products. In 

 stored grains they cause great economic loss not so much by what they eat 

 (although populations of astronomical figures are found at times) as by the 

 damage that they cause by changing the moisture content of the medium 

 and initiating the growth of moulds. In the state of nature they are usually 

 found on rotting leaves and plant debris, on the bark of trees, on decaying 

 bulbs and tubers, on fresh and putrid mushrooms, and in the nests of mam- 

 mals and birds, where presumably they live on organic wastes and bits of 

 hair and feathers. In speaking of ecological niches it is interesting to note 

 that, even as the family may be divided taxonomically into two quite dis- 

 tinct subfamilies on morphological grounds, it may also be separated into 

 the same two subfamilies on the basis of the type of habitat preferred. 

 Almost without exception the members of the one group prefer to live in 

 substances having a low moisture content (20 to 30 per cent), viz., wheat, 

 seeds, and stored farinaceous products, whereas the members of the other 

 group can exist only in a very humid habitat, many seeming to prefer a 

 place where they are wading in a film of water. As a result of these studies, 

 I am persuaded that the members of the former group can, and do, eat the 

 more solid organic substances such as the germ and endosperm of seeds, 

 whilst those of the latter group live fairly exclusively on the fungi and 

 moulds growing on the excessively damp substratum that they prefer. Fur- 



