8o 



ECONOMIC ZOOLOGY 



spider, Latrodectus mactans, Fig. 60, really is at times, dangerously 

 poisonous to man. Latrodectus is widely distributed over the earth 

 and is generally feared. In the Americas there are three species of this 

 genus, the best known being the one named above, which is found from 

 the northern part of the United States to the southern end of South 

 America, it is common in our southern and southwestern states. The 

 male has an elliptical abdomen and is about 12 mm. in length. It is 

 a "sooty-black or dark brown color with a conspicuous small blotch 



or blotches of vivid red on the under side 

 of the abdomen. This blotch or pair of 

 fusing blotches has the rough outline of 

 an hour-glass. However it varies much 

 in shape." The position and vivid color 

 of this spot on the dark body are char- 

 acteristic. 



Kellogg discribes a case in California 

 in which most serious results followed 

 the bite of this spider. Enormous swell- 

 ing of the bitten organ, intense pains 

 with cramp, labored respiration, slowed 

 heart-beat, etc., were noted. A cat in- 

 jected with an attenuated dose of the 

 poison died in 10 minutes, other animals 

 reacted strongly. 



FIG. 59. "Tarantula" 

 spider, sp. X^3- 



"A diadem spider of 1.4 gr. (weight), 

 contains sufficient poison to destroy com- 

 pletely all the corpuscles in 2.5 liters of 

 rabbit's blood." 



Doubtless the effects of the bite of these spiders are more marked 

 with some persons than with others and with the same person at dif- 

 ferent times. Kobert says they may "produce by their bite the most 

 serious general results, and are capable of killing even men." The bite 

 of the Tarantula may often be painful without being serious. 



Of poisonous spiders Comstock (93) says: "The so-called Tar- 

 antula (Heteropoda) that is frequently brought to the North in 

 bunches of bananas is often described as the cause of serious injury. 

 This however, though a large spider, is an inoffensive one. Mr. 



