Latrodectus Geometricus Koch on Luzon

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  1. 1.Latrodectus geometricus Koch is for the first time reported from the Philippine Islands. Specimens were collected at Clark Air Force Base, Camp O'Donnell, and Ft. Wm. McKinley, all on Luzon Island.
  2. 2.This spider is a common house-infesting species at Clark Air Force Base, where its habits are similar to those of L. mactans Fabr. in the United States. Observations on longevity, habits, and egg sack production are based upon study of a colony of spiders maintained in the laboratory.
  3. 3.Effects of venom on mice, guinea pigs, and cats were similar to those reported by other workers using venoms of L. mactans and L. hasseltii, but indicate a lower degree of toxicity for laboratory animals. Pathological findings included necrosis and fatty infiltration of the liver, and hemorrhage in the liver, lungs, and pericardium.
  4. 4.There are no records of humans bitten by geometricus on Luzon. However, demonstrated toxicity of geometricus venom, combined with close resemblance of this spider to mactans and hasseltii, suggests the possibility that some of the bites credited to those species may have been caused by geometricus, which occurs in the ranges of both species.
  5. 5.DDT in spray, aerosol, and powder form is effective in destroying both adult and juvenile spiders. Egg sacks and spiders found in living quarters may be easily swept down and crushed. Natural enemies of Luzon include unidentified predacious wasps, and the egg sack parasite, Eurytoma arachnovora Hesse, never before reported from the Philippine Islands.

Author Notes

Capt., MSC, USA, 18th Medical Group, APO 74, c/o Postmaster, San Francisco, Calif.

Major, MC, USA.

1st Lt., MSC, USA.