Handbook of Medical Entomology

by William A. Riley; O. A. Johannsen

Of the Old World Lycosidæ there is no doubt that several species were implicated as the supposed cause of the tarantism. In fact, as we have already noted, the blame was sometimes attached to a scorpion. However, there seems to be no doubt that most of the accounts refer to the spider known as Lycosa tarantula.

There is no need to enter into further details here regarding the supposed virulence of these forms, popular and the older medical literature abound in circumstantial accounts of the terrible effects of the bite. Fortunately, there is direct experimental evidence which bears on the question.

Fabre induced a common south European wolf-spider, Lycosa narbonensis, to bite the leg of a young sparrow, ready to leave the nest. The leg seemed paralyzed as a result of the bite, and though the bird seemed lively and clamored for food the next day, on the third day it died. A mole, bitten on the nose, succumbed after thirty-six hours. From these experiments Fabre seemed justified in his conclusion that the bite of this spider is not an accident which man can afford to treat lightly. Unfortunately, there is nothing in the experiments, or in the symptoms detailed, to exclude the probability that the death of the animals was the result of secondary infection.

As far back as 1693, as we learn from the valuable account of Kobert, (1901), the Italian physician, Sanguinetti allowed himself to be bitten on the arm by two tarantulas, in the presence of witnesses. The sensation was equivalent to that from an ant or a mosquito bite and there were no other phenomena the first day. On the second day the wound was inflamed and there was slight ulceration. It is clear that these later symptoms were due to a secondary infection. These experiments have been repeated by various observers, among whom may be mentioned Leon Dufour, Josef Erker and Heinzel, and with the similar conclusion that the bite of the Italian tarantula ordinarily causes no severe symptoms. In this conclusion, Kobert, though firmly convinced of the poisonous nature of some spiders, coincides. He also believes that striking symptoms may be simulated or artificially induced by patients in order to attract interest, or because they have been assured that the bite, under all circumstances, caused tarantism.

The so-called Russian tarantula, Trochosa singoriensis ([fig. 7]), is much larger than the Italian species, and is much feared. Kobert carried out a series of careful experiments with this species and his results have such an important bearing on the question of the venomous nature of the tarantula that we quote his summary. Experimenting first on nearly a hundred living specimens of Trochosa singoriensis from Crimea he says that:

"The tarantulas, no matter how often they were placed on the skin, handled, and irritated, could not be induced to bite either myself, the janitor, or the ordinary experimental animals. The objection that the tarantulas were weak and indifferent cannot stand, for as soon as I placed two of them on the shaved skin of a rabbit, instead of an attack on the animal, there began a furious battle between the two spiders, which did not cease until one of the two was killed."

"Since the spiders would not bite, I carefully ground up the fresh animals in physiological salt solution, preparing an extract which must have contained, in solution, all of the poisonous substance of their bodies. While in the case of Latrodectus, as we shall see, less than one specimen sufficed to yield an active extract, I have injected the filtered extract of six fresh Russian tarantulas, of which each one was much heavier than an average Latrodectus, subcutaneously and into the jugular vein of various cats without the animals dying or showing any special symptoms. On the basis of my experiments I can therefore only say that the quantity of the poison soluble in physiological salt solution, even when the spiders are perfectly fresh and well nourished, is very insignificant. That the poison of the Russian tarantula is not soluble in physiological salt solution, is exceedingly improbable. Moreover, I have prepared alcoholic extracts and was unable to find them active. Since the Russian spider exceeds the Italian in size and in intensity of the bite, it seems very improbable to me that the pharmacological test of the Italian tarantula would yield essentially other results than those from the Russian species."

To the Avicularoidea belong the largest and most formidable appearing of the spiders and it is not strange that in the New World they have fallen heir to the bad reputation, as well as to the name of the tarantula of Europe. In this country they occur only in the South or in the far West, but occasionally living specimens are brought to our northern ports in shipments of bananas and other tropical produce, and are the source of much alarm. It should be mentioned, however, that the large spider most frequently found under such circumstances is not a tarantula at all, but one of the Heteropodidæ, or giant crab-spiders, ([fig. 8]).