200 Acarology 



entire while iv is divided into basi- and telofemur. Three pairs of 

 genital suckers are present. 



Figure 142 Petralycus unicornis 

 Grandjean. Venter of female. (After 

 Grandjean 1943) 



Figure 143 Petralycus unicornis 

 Grandjean. Dorsum of female. (After 

 Grandjean 1943) 



Genera: 

 1 



Pachygnathus Duges, 1834 



Type. Pachygnathus villosus Duges, 1836 



Bimichaelia Thor, 1902 (= Michaelia Berlese, 1884 nom. praeocc.) 



Type. Michaelia augustana Berlese, 1884 



Petralycus Grandjean, 1943 



Type. Petralycus unicornis Grandjean, 1943 



Discussion: These mites are found in humus and 

 vegetable debris and in the soil. They are prob- 

 ably predators but very little is known of them. 

 Bimichaelia diadema Grandjean has a larva, two 

 tgure et)a- ^^^jyg nymphal stages, and an adult stage; Bimi- 



lycNS unicornis j f a •> o ' 



Grandjean. Lateral chaelia arhusculosa Grandjean and Petraycus uni- 

 view of chelicera. cornis Grandjean have three nymphal stages. A 

 1943T "^'^^ ^^'^" Bimichaelia sp. from southern United States was 



studied and found to have the tracheal system. 

 References: 



Grandjean, F. 1942. Quelques genres d'acariens appartenant au groupe 

 des Endeostigmata (2 Ser.) Premiere partie. Ann. des Scr Nat , Zool., 

 Ser. 11, 4:85-135. 



. 1943. Quelques genres d'acariens appartenant au groupe des En- 

 deostigmata (2 ser.) Deuxieme partie. Ann. des Sci. Nat., Zool., Ser. 

 11, 5:1-59. 



