212 VENOMOUS ANIMALS: PROTOZOA TO ARTHROPODA 



Historical. — ^The study of spider-stings may be said to be modern, 

 and to begin with Blackwell in 1855, but it was Robert in 1893 who 

 gave the fundamental data concerning these poisons. He main- 

 tains that, in addition to the secretion of the poison gland, there 

 is a toxalbumin which permeates every portion of the body of the 

 animal, and in some species of animals is mixed with the venom. 

 He considers that the secretion of the poison gland only gives 

 rise to local symptoms, and that the general symptoms are due to 

 this toxalbumin, and that it is because of this admixture in Latro- 

 dectus that the bite may cause severe symptoms and even death 

 in human beings. The common European garden spider {Epeira 

 diadema) only causes local irritation, because the toxalbumin, 

 though present in the body, is not mixed with the poison of the 

 poison gland. He also describes a haemolytic action in both Epeira 

 and Latrodectus. 



Sachs has contributed a paper in which he carefully studies this 

 haemolysin, which he calls arachnolysin, and Wilson has recently 

 written an excellent monograph on the spider-bites. 



Classification. — Spiders are divided into two suborders as 

 follows 



I. Spinning organs situate far anterior to the anus. Eleven 

 tergal plates on the dorsal surface. (Mesothelae.) 

 n. Spinning organs situate just in front of the anus. No 

 tergal plates visible. (Opisthothelse.) 



The Opisthothelse are the only forms which concern us, and they 

 are divided into tribes as follows:— 



A. Only anterior pair of spinning organs present. (Megalo- 



morphse.) 



B. Two pairs of viramous spinning organs present. (Arachno- 



morphse.) 



The Megalomorphse include — ■ 



I. Without large maxillary process on the base of the palp — 



1. Feet furnished with apical tufts or pads of hair. 



(Aviculariidae.) 



2. Feet not so furnished. (Ctenizidae.) 



n. With large maxillary process on the base of the palp. 

 (Atypidse.) 



The bird-eating spiders ' Mygale ' come under the Aviculariidae. 

 The Arachnomorphse include : — 



The Epeiridae with Epeira diadema, the Theridiidae with 

 Latrodectus, the Lycosidae with the Tarantula spider. 



Geographical. — All genera of spiders appear to be poisonous, but 

 the most important are: Latrodectus mactans. Chili; L. scelio, 

 the katipo of New Zealand; Theraphosa avicularia L., South 

 America ; T. hlondi Latr. ; T. javanensis Walck. ; Chiracanthum 

 mitrix Walck.; Theridium tredecim guttatum F., France and Italy; 



