NEW OR, LITTLE-KNOWN ACARl. 37o 



and general appearance, it seems probable that the genera 

 Fsorergates and Demodex are related to one another. 



Speleorchestes ventriosus, sp. n. 



2 . This new saltatorial mite differs from 8. pochoroides, mihi 

 in being much stouter in appeai'ance ; the abdomen is especially 

 wide (hence the specific name ventriosus), being much stouter 

 than in >S. jyoduroides. Ovipositor when protruded provided with 

 a basal collar-like structure or sheath as in S. poduroides, but it 

 is longer than in that species, its length exceeding the distal part 

 of the ovipositor that projects beyond it (whereas in S. poduroides 

 the collar is much shorter than the part of the ovipositor that 

 projects beyond it). Shape of hairs and their distribution much 

 as in S. poduroides. 



Owing to its rather squat appearance, this new species of 

 Speleorchestes somewhat resembles JVanorckestes, but the anterior 

 part of the cephalothorax is quite separa,te and distinct from the 

 posterior portion, not being enclosed by it laterally ; posterior 

 part of cephalothorax much narrower than the abdomen and 

 divided from it by a distinct constriction (whilst in Nanorchestes 

 the posterior part of the cej)halothorax is almost as wide as the 

 abdomen and only separated from it by a slight groove). 



Length (including chelicerje) 317 /x ; width of anterior (cephalic) 

 part of cephalothorax 62-67 //. ; width of posterior (thoracic) part 

 of cephalothorax 107-110 /x ; width of abdomen 155-160 /x. 



Habitat. Hindhead, Surrey ; a number of specimens collected 

 by the author under stones near the path running above the 

 natural hollow known as " the Devil's Punch Bowl " (just 

 below Hindhead Beacon), May 1918. 



Speleorchestes poduroides Hirst. 



I have added a few moi'e measurements for comparison with 

 those of S. ventriosus, sp. n. 



Length (including chelicer?e) 278-290 /a ; width of anterior 

 (cephalic) part of cephalothorax 58-60 /i ; width of posterior 

 (thoracic) part of cephalothorax 82-85 j.l ; width of abdomen 106- 

 115ju. 



Key to British Species of Saltatorial Mites (Genera Nanorchestes 

 and Speleorchestes). 



Body short and wide ; anterior part of cephalothorax on- 

 closed laterally by the posterior part Nanorchestes Tops. 



& Trouess. 

 Dorsal hair on chelicera slender and divided into two 



plumose branches N. coUiims Hirst 



(Mendip Hills). 

 Dorsal hair on chelicera rather short, stiff, rod-like, and 



not divided JSf. ampli ibins Tops. 



& Trouess. 

 (Littoral species.) 

 l3ody more elongated ; anterior part of cephalothorax 



fi'ee (not enclosed laterally by posterior part) Speleorchestes Trgdh. 



