THE INTERNATIONAL 



JOURNAL OF MICROSCOPY & NATURAL SCIENCE^^^^^^i^ 



THE JOURNAL OF THE POSTAL MICROSCOPICAL soCir^ ^^^^^^"^ 



^''Knowledge is not given us to keep, but to impart ; its 

 is lost in concealment y 



[The Editor does not hold himself responsible for the views of 

 the authors of the papers published.] 



preai&ential Hbbresa: '' Mbat i6 a Spiber ? '' 



By Dr. J. S. Walker. Plate I. 



HE scientific characteristics of an insect is a crea- 

 ture whose body is divided into three parts, has 

 two antennas, six legs, and passes through four 

 stages of metamorphosis ; but a spider is not an 

 insect. The spider belongs to the Araneidea, an 

 order of the Arachnida which, in common with 

 insects, is a sub-class of the Arthropoda. The 

 body of a spider is made up of two parts : the 

 cephalothorax and the abdomen. 

 There are nine orders of Arachnida : — 

 I. — Scorpions ( Scorpio dea), in which the respiration is by air- 

 chambers, and there is a post-abdomen ending in a claw. 



2. — Cheliferidea, in which the respiration is by tracheae; the 

 abdomen is not distinctly separated, and the maxillary palpi have 

 two claws. 



3. — Acaridea, with unsegmented abdomen, which is united to 

 the cephalothorax. 



4. — Spiders {Araneidea\ in which the unsegmented abdomen 

 is distinct from the cephalothorax. 



International Journal of Microscopy and Natural Science. 

 Third Series. Vol. VII. b 



