1899] 



ENTOMOLOGICAL SOCIETY. 



89 



Spiders differ from insects in the under-mentioned, as well as in some other, respects. 



(a) In the spiders the head and thorax are nnited in what is called a cephalo-thorax. 

 In the insects the head and thorax are distinct. (Fig. 43, upper surface of a spider ; 

 fig. 44, lower surface — both much enlarged). 



(o) Spiders have no wings. 



(c) They breathe by means of lung-sacs, through tracheae which open under the 

 abdomen. 



(d) Their eyes are simple, not compound as in the insects. 



(e) They have eight legs. Insects proper, in their perfect state, have only six. 



(f) Their abdomens have no segments. 



(g) After leaving the egg they grow, but undergo no metamorphoses. The insect 

 passes from larva to pupa, and from pupa to imago. 



Spiders have been divided into three tribes, according to the number of their eyes :* 



I. Octonoculina — Eight-eyed spiders. 



II. Senoculina — Six-eyed spiders. 



III. Binoculina — Two-eyed spiders. 



The families are named in most cases from the habits of the species they severally 

 include. 



Thus in the first tribe among others are found : — 



The Salticidse or Leapers (Fig. 45). 



The Thomisidse, or Binders (Fig. 46. The arrangement of the eyes is shown below). 



The Drassidse, or Seizors (Fig. 47). 



The Linyphiidse, or Weavers (Fig. 48), etc., etc. 



The form, colour and arrangement of the eyes assist the 

 \<*turalist in determining the genera of spiders, thus : 



The genus Sphasus has two large and six small eyes. 



The genus Salticus (Fig. 45) ha3 the eyes in three rows. 



The genus Philodromus has them in two crescents. 



The genus Pholcus has the eyes on prominent black 

 spots, etc., etc. 



The species are determined from peculiarities of form, 

 colour and markings. 



The spider has eight 

 seven-jointed legs, termin- 

 ated in every instance with 

 three toothed-claws (Fig. 

 49), or with two such claws 

 and a brush (Fig. 50). 

 This may fitly be called a 

 hand-brush, for the creature 

 uses it for dusting its web. 



Projecting from the 

 spider's head are two six- 

 jointed palpi, which are so 

 large that they might al 

 most be mistaken for an- 

 other pair of legs ; and 

 between these are the for- 



Fis. 48. 



Fig. 49. 



^Blackwall's " Spiders of Great Britain and Ireland. 



