37 



IV. REPRESENTATIVE ARTHROPODA* 



IMPORTANT REFERENCES f 



In addition to the general references and to special papers cited in the text, 

 see Comstock, '95, '12; Huber, '99-03; Megnin, '80, 'o5; Nuttall, '99; 

 Osbom, '96. 



Class ARACHNIDA 



Order ACARINA 



For characteristics of this order, see p. 13 of this outline and for 

 general discussion of the group see, especially. Banks, '04, Ewing, '12. 



Superfamily TROMBIDOIDEA 



Harvest mites — Last part of palpus forms a thumb to the preced- 

 ing, which ends in a claw. 



Trombidium holosericeum — "Leptus irritans", the "red bug", or 

 so-called "jigger" or "chigger". Minute, exceedingly annoying 

 parasite of man and some animals in our central and southern states, 

 England, South of France, Germany, and tropics, burrowing into 

 the skin and causing intense itching, redness and swelling. Distinct 

 from the true "chigoe", or jigger, which is a flea. 



Description — Red, almost microscopic. 230/* longest diameter, 

 larva of a free living mite. Six legs, with prominent claws on the tips, 

 and with a powerful hypostome which they drive through the skin. 



Habits and life history — Only the larvae parasitic and they on man 

 abnormally so, for they die after entering the skin. Common 

 species on the housefly in autumn and on grasshoppers. Adults 

 predaceous, one species commonly feeds on grasshopper eggs. Adults 

 hibernate and deposit eggs in or on the ground. 



*The question of the relation of Arthropods to disease is the subject of a 

 special course, and hence this important phase will be but incidentally consid- 

 ered here. For special bibliography see Riley, '12a. 



fin addition, the publication of the Bureau of Entomology and the Bureau 

 of Animal Industry should be consulted, whether specifically cited or not. The 

 bulletins of the Public Health and Marine Hospital Service also contain much 

 of importance along this line. 



