Trombidiformes 169 



Genera: 



1. Tarsonemus Canestrini and Fanzago, 1876 



Type. Chironemus miniisculiis Canestrini and Fanzago, 1876 



2. Avrosia Oudemans, 1928 



Type. Acariis translucens Nietner, 1861 



3. Hemitarsonemus Ewing, 1939 



Type. Tarsonemus tepidariorum Warburton, 1904 



4. Pseiidotarsonemoides Vitzthum, 1921 



Type. Pseudotarsonemoides eccoptogasteris Vitzthum, 1921 



5. Tarsonemella Hirst, 1923 



Type. Tarsonemella africana Hirst, 1923 



Discussion: The tarsonemids illustrate a highly simplified type of 

 life cycle. There are only four stages: egg, larva, quiescent nymphal 

 stage in which the larva transforms into a mature adult (there being 

 no active nymph) , and the adult. The males are heter- 

 omorphic and the fourth pair of legs is used for clasp- 

 ing the female during copulation. This pair of legs is 

 extremely important in the identification of the species. 

 The females lay one egg at a time, the hysterosoma 

 being adapted with a series of overlapping segments to 

 allow for the expansion of the body. The mites appear 

 to prefer humid, sheltered conditions and disappear 

 in many cases after the onset of high temperatures. '§^"^^ 



„ . , . Tarsonemus 



This is a widely distributed group of mites, being phyllopherus 

 found throughout the warmer parts of the world. Al- Ewing. Leg iv 

 though some of the species appear to be scavengers p -^^^Vq/^^ 

 and predators, many are of economic importance 

 because they cause serious injury to plants. The following species 

 which have proved to be injurious to their hosts indicate the wide 

 range of host plants and the importance of this family. 



Tarsonemus pallidus Banks is a serious pest of cyclamens in the 

 United States and of strawberries in Europe; T. waitei Banks injures 

 the peach tree in various parts of the United States; T. spirijex Marchal 

 damages oats in Europe and has been reported from Arizona and 

 Kansas in the United States; T. laticeps Halbert, the bulb scale mite, 

 is a pest of narcissus bulbs in Europe and the United States, causing 

 reduction in the number of flowers produced; T. ananas Tryon is an 

 agent in the transmission of a pineapple rot in Australia. Hemitarso- 

 nemus latus (Banks) is listed as being a pest of a wide assortment of 

 plants throughout the world, such as tea in Ceylon, Cinchona sp. in 



