TEGENERIA MEDICINALIS. 



THE SECONDARY CHARACTERS. 



TEGENERIA. Never more than two pulmonary sacs placed 

 under the abdomen, and communicating with the exterior air 

 by spiracula. Heart consisting of a large cylindrical vessel, 

 sending the blood through the arteries to the different parts 

 of the body, and receiving by the veins that which has trav- 

 ersed the respiratory organs. Feet always four pairs. 



THE SPECIFIC CHARACTERS. 



TEGENERIA MEDICINALIS. Eyes arranged in a slightly 

 curved line. These construct in the interior of our houses, in 

 angles of walls, &c., an angular web, at the upper part of 

 which is a tube in which they remain motionless. 



NATURAL HISTORY. 



The genus Aranea of Linnaeus has been divided by sub- 

 sequent naturalists into several genera, of which the Tegene- 

 ria of Walckenaer is the one that includes the medicinal 

 species of spider. The Tegeneria domestica of Europe and 

 Teg-eneria medicinalis of this country are the particular species 

 which have attracted most attention. These well-known an- 

 imals, if not among the most admired, are undoubtedly 

 among the most interesting of the annulose world from their 

 habits and mode of life. They differ essentially in their in- 

 ternal structure from insects proper, and their external form 

 is so peculiar that they are easily recognized. The family of 

 spiders is not always arranged among insects, and, strictly 

 speaking, their structure is different in some important par- 

 ticulars. The body is composed of two pieces only, the head 

 being united with the thorax, and the feet are always eight 

 in number. The cephalo-thorax appears as if composed of 

 but a single segment, and is covered with a sort of horny 

 buckler, generally oval, to which the abdomen, consisting of 

 a soft and tumid mass, is appended. Generally they have 

 eight eyes, though sometimes only six, variously disposed in 

 the different genera, but always simple. The mandibles ter- 

 minate in a very short movable hook, having near its ex- 

 tremity a small aperture, which serves as a passage for the 

 poison. The legs are inserted almost in a circular manner 

 around the cephalo-thorax ; they are all nearly of the same 

 form, and each is composed of seven joints, the last being 



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