Persons unfamiliar with spiders find it difficult to distinguish the young from the old, and male from female. This is caused, in part, by the great differences between different ages and sexes of the same spider, on account of which they are supposed to belong to distinct species. The adult males and females, however, are easily distinguished from each other, and from the young, by the complete development of organs peculiar to each sex, the palpal organs on the ends of the palpi in the males, and the epigynum, a hard swollen place just in front of the opening of the ovaries in the females. Usually the males are smaller than their partners, and have, in proportion to their size, smaller abdomens and longer legs. They are generally darker colored, especially on the head and front part of the body, and markings which are distinct in the female coalesce and become darker in the male. In most species these differences are not very great, but in some, Argiope and Nephila for examples, where the males are about one-tenth as large as the females, one would hardly suppose, without other evidence, that the males and females had any relationship to each other. The palpal organs and the epigynum are sexual characters which do not attain their functional value until after the last moult has been effected. Spiders are naturally very selfish creatures. Their chief concern in life seems to be the gratification of their desires for food. They are eminently unsocial, the sexes preferring to live solitary lives. It is only when actuated by amatory influences that the females will tolerate their weaker lords, and in some instances it is only by stratagem and agility that the latter are able to accomplish the fulfilment of the law of their being, the females by their ugly, vicious tempers resisting to the utmost. In the case of Agalena the male is the stronger of the two. He, at the proper time, when the reproductive cells are matured, takes the female in his powerful mandibles, lays her gently on one side, and inserts one of his palpi, whose little sacs had previously been filled with the fecundating discharge, into the epigynum underneath. After a time, necessarily brief, he rises on tiptoe, turns her around and over, so that she comfortably lies on the other side, her head being in the opposite direction, and inserts the other palpus. All through the operation the female lies as though she was dead. The ends of nature being served, the sexes separate, the male returning to the solitary life he previously led, while the female busies herself in providing for the duties of maternity.