234 FIELD ZOOLOGY. 



Acarina — Mites and Ticks. 



These Arthropods have the abdomen unsegmented 

 and fused with the thorax. They include the mites and 

 the ticks. The majority of them are very small, though 

 some of the ticks reach considerable size. All mites, 

 except one family, hatch from eggs. In the case of this 

 exceptional mite family, the eggs remain in the adult 

 body after cell division in the egg begins, and until the 

 segmentation of the young mite into head and abdomeno- 

 thoracic regions with rudimentary legs. These young 

 mites — or larvae, properly speaking — are then discharged 

 to begin their separate, individual existence. 



Young mites usually have three pairs of legs, but 

 develop a fourth pair while maturing. Some mites 

 produce galls similar to those produced by the gallflies, 

 but there is always an opening through which the young 

 mite escapes. The itch mite infests the human tribe and 

 burrows beneath the skin. With the exception of the 

 mite which infests pear trees, all mites have four pairs 

 of legs. The cattle tick is a true Acarina, but the sheep 

 tick is a dipterous insect. 



Mites are sometimes found on plants. The best- 

 known plant mite is the so-called red spider which so 

 often injures house plants. In a dry summer it will 

 sometimes attack fruit trees. It thrives only in a hot, 

 dry atmosphere; hence the effective treatment of the 

 pest is water and plenty of it, sprayed onto the under 

 as well as the upper sides of the leaves. The mite seems 

 to work mainly from the lower side, up through the juicy, 

 green portion of the leaf, leaving the remaining upper 

 part to wither and drop off. 



