Alexander Ivanovitch Petrunkevitch (Russian: Александр Иванович Петрункевич, December 22, 1875 in Plysky near Kyiv, now Ukraine – March 9, 1964 in New Haven) was a Russian arachnologist. From 1910 to 1939 he described over 130 spider species. One of his most famous essays was "The Spider and the Wasp." In it he uses effective word choices and some comic touch.
His aristocratic father, Ivan Illitch Petrunkevitch, was a liberal member of the First Duma and founded the Constitutional Democratic Party. After finishing his studies in Moscow and in Freiburg under August Weismann, Alexander settled in Yale in 1910, becoming a full professor in 1917. Apart from describing present-day species, he was a major figure in the study of fossil arachnids, including those in amber and from the Coal Measures. He also experimented with live specimens and worked on insects.
Petrunkevitch's formulation of the principle of plural effects (every cause is potentially capable of producing several effects) and the principle of the limits of possible oscillations (the number and the nature of the effects which actually take place may vary within definite limitations only) is well known, both in biology and psychology.[1]