Abstract

One hundred and fifty mg/kg of psilocybin per os, 1 g/kg of mescaline per os, or a 30% increase in body weight made spiders build webs the following day with a shorter thread. The weight increase also caused a thicker thread measured as higher nitrogen content per meter thread. This can be explained by assuming that the heavier spider has to build a thicker thread to hold its own weight while it has not enough material to build it of equal length. Removal of weight led only after 3 and more days to a return to thread thickness and length of control webs. However, these heavier spiders repeated their web-building at a normal frequency.

The shorter thread after psilocybin application was not thicker nor were any changes in web proportions observed. Further increase in the dose of psilocybin caused a dose-dependent decrease in web-building frequency, and none out of 33 spiders whlich had received 6 g/kg psilocybin built a web on the following day. This may be comparable to the relaxing effect of psilocybin in higher animals or be attributed to an effect on thread production. The mescaline webs with shorter threads also showed a smaller catching area and more irregular angles. A higher dose diminished web-building too. The ratio between effective doses of mescaline and psiloeybin was about 1:10 measured as changes in thread length or web-building frequency, with psilocybin being the more potent drug.