436 



ARACHNIDA 



H. pikei Peckham (Fig. 687). Body 8 mm. long and very slender, 

 with the abdomen twice as long as the cephalothorax and longer than the 

 hind legs; abdomen with a very broad, black stripe having 3 notches on 

 each side; rest of the body whitish; front legs brown, others white: 

 common on sand and grass, on which it often lies with the legs parallel 

 to the body, so that it would be seen with difficulty. 



7. Synemosyna Hentz. Cephalothorax and abdomen each with a 

 deep dorsal depression; middle of the body slender, front middle eyes 

 large, the rest small: 1 species. 



S. formica Hentz. Ant-like spider (Fig. 688). Body 6 mm. long 



and very slender; cephalothorax naiTowed behind and the abdomen in 



front, and each has a deep dorsal depression in the middle ; 



color black with yellowish markings: the spider resembles 



an ant in shape and method of walkmg. 



Order 8. ACARINA * 



The mites. Small arachnids, in which cephalothorax 

 and abdomen are unsegmented and so joined that the short, 

 thick body is more or less ovoid or globose in shape. In 

 some forms a suture separates the f onvard part of the body 

 with two pairs of legs from the hinder part with the two 

 hinder pairs; in a few also the abdomen is elongated and 

 annulated, although not segmented. The six pairs of ap- 

 pendages are well developed and consist of the mandibles 

 and pedipalps and four pairs of legs, except in the Erio- 

 phyidae, which have but two pairs. The mandibles may be 

 chelate or formed for piercing and sucking. The pedipalps are usually 

 more or less leg-like, with five joints or less, and in some forms they 

 are chelate or subchelate; the basal joints may form plates called 

 the maxillae, or they may unite to form a lip or labium. Accessory 

 mouth parts are often present, as a hypostome or under lip and tongue, 

 and an upper lip or epistome; the latter may be united with the 

 lip below to form a tube called the rostrum, from which the man- 

 dibles protrude. The legs are usually 5-jointed and end each with two 

 claws. The external surface of the body is more or less covered with 

 tactile hairs or with scales. Eyes are either present or absent. The 



* See "A Treatise on the A carina or Mites," by Nathan Banks, Proc. U. S. Nat. 

 Mus., Vol. 2.S, p. 1, 1905. "A Catalogue of the Acarina or Mites of the United 

 States," by Nathan Banks, same. Vol. 32, p. 595, 1907. "The Life History and 

 Binomics of Some North American Ticks," by W. A. Hooker and others, Bull. lOG, 

 Bur. Ent, U. S. Dept. Ag., 1912. "New Mites," by H. E. Ewing, Bull. Am. Mus. 

 Nat. Hist., Vol. 32, p. 93, 1913. "The Acarina," by N. Banks, Rep. 108, Bur. Ent., 

 1915. 



Fig. 688 

 Syuemostfna 



formica 

 (Emerton). 



