Just Jaunting Round

The black widow spider

Page 1 of an article by George F. Knowlton entitled, "The Black Widow spider," issued as Leaflet no. 57 by the Utah Agricultural Experiment Station. Utah State Agricultural College, Logan, Utah, April 1935

splder was caged upon the clipped abdomen oflarge guinea pig By pressing with forceps upon the logs of the spider it was readily induced to bite the gulnea pig four times within about one minute Twelve minutes later the guinea pig was noticeably uneasy it shifted about hunched up and breathed fast After 21 minutes the guinea pis was even more uncasy shifting about constantly and rinding its teeth At the end of 25 minutes breathing seemed more labored and occesionally trembling occurred At the end of 42 minutespurplish area had appeared around each bite but the shifting about had lessened At the end of three andhalf hours the purple areas had almost disapDeared slight temperature of6 was noted as well asspasmodic Focking to the lett andjerking of the head an elevation of the right side of the body and continued fast breathing After six andhalf hours the guinea pig became rather lothargic and its abdomen felt hot to the touch An hour later the abdomen appeared somewhat bloated and felt rather rigld At the expiration of 22 hours the Euinea pig med gaunt somewhat comatose and breathed convulsively havingtemperature increase of about8 degree At the end of 27 hours the guinea pig was dead The black widow spider Latrodectus mactans Fabr issmall jot black spider withconspicuous red or orange-colored hour-glass shaped area on the underside of its abdomen Fig The coal-black adult fomale ranges In size from to nearly inch long it is shiny black above withlarge globular abdomen andmuch smaller head and thorax cephalothorax and long legs The male is only about half the size of the female and is marked With red or orange dorsal and four lateral pale stripes along the abdomen above The maturing young of both sexes aro similar in appearance The pedipalpi are much enlarged in the mature male The round egs cases made by the females are cach about the size of he abdomen of mature fomale or larger wWhitish to graylsh-white In color and silky When the young spiders from one to threo ogg cases were reared In the laboratory only one orof the young reached maturity the remainder being devoured by the others Lite History During late spring and summer the female constructs number of whitish balloon-sbaped egs cases at intervals of fromto 24 days oach case contains from 200 to 900 or more eggs and is hung in the upper parts of the web Often two or even three egg cases will have been constructed before the young spiders begin to emerge from the first These kg cases appear to be most frequently constructed during the night One female was brought into the Utah Station Laboratory with two egg cases three additional cases were constructed befor this individual dled about five wecks lator Anothor fomale constructed two egg cases and lived for several weeks without being fed her abdomen kept decreasing in size Apparently the younger adults survive the winter in sheltered places the older females dying during late summer and fall Lawson records individual fomales constructing as many as nine egg cases under laboratory conditions He states that It is the general rule for individusls becoming adult one season to lay their eggs during the next summer IIlingworth reports that after one mating as many as 15 gg sacks have been made by ono female fn captivity Lawson ks5 7 Soc otesAme on theLife BT Historys of the Hour-glass Spider 5diotine Black Widow Spider In Proc Hawaiian Bnt Digital image 2003 Beckwith Family Al rights reserved