Spiders of the Genus Latrodectus 
i7 
Robert concludes that in its chemical nature the poison is neither 
an alkaloid, nor a glycoside, nor an acid, but a toxalbumen, or poison¬ 
ous enzyme which is very similar to certain other animal poisons, 
notably that of the scorpion. 
9 . Latrodectus mactans; (a) female, x 3; ( b ) venter of female; (e) dorsum of male. 
After Comstock. 
The genus Latrodectus is represented in the United States by at 
least two species, L. mactans and L. geometricus. Concerning L. 
mactans there are very circumstantial accounts of serious injury and 
even death in man*. Latrodectus mactans is coal black, marked with 
red or yellow or both. It has eight eyes, which arc dissimilar in 
*Dr. E. H. Coleman (Kellogg, 1915) has demonstrated its virulence by a series 
of experiments comparable with those of Kobert. 
