In cases where the males alone stridulate it is always supposed that this “music” serves the purpose of a lure, or acts as an excitant, to the female, even though inaudible to human ears. But there are many people who are unable to hear the shrill squeal of our native bats. Yet no one doubts but that all bats hear it. The argument as to the absence of any sense of hearing in certain Spiders is based on their failure to respond to the vibrations of a tuning-fork, but this evidence is not conclusive. Neither is it safe to infer that the presence of stridulating organs in the adult and immature stages of both sexes, in some species, precludes their recognition as secondary sexual characters. They may serve the double purpose of sexual excitants and terrifying enemies, their motive being expressed by the quality of the sound as certainly as the timbre of the human voice may express rage or pleasure. Neither Spiders nor Scorpions exhibit any very striking secondary sexual characters. As a rule the female is the larger, often strikingly so. Bright colours are rare, and are met with only among the Spiders, wherein sometimes the male, sometimes the female, is the more resplendent; where bright colours—apple-green, red and yellow—do occur, they seem rather to be of the type known as Anti-cryptic, or aggressive resemblance colours. That is to say, they are hues developed to deceive prey by reason of the likeness they afford the wearer to its surroundings. Thus, for example, one of our native Spiders (_Tibellus oblongus_) is straw-coloured, and has an elongated body, which is therefore seen with difficulty amid dry grass and rushes which are the haunts of the species. _Misumena vatia_, one of the Crab-spiders, resembles the flowers on which it is accustomed to lurk for its prey. It is of a variable hue, commonly yellow or pink, and a favoured lurking-place is near the blooms of the great mullein (_Verbascum thapsus_), where it seizes upon bees coming for honey. Exotic relatives of this species afford far more striking illustrations of this kind. One has a pink, three-lobed body which bears a striking likeness to a withered flower, and it exhales a sweet odour of jasmine. Insects attracted by the smell are thus readily pounced upon. Dr. Trimen, of Cape Town, describes a rose-red species which exactly matches an oleander flower, and to complete the deception the abdomen is marked with white. The same observer, approaching a bush of the yellow-flowered _Senecio pubigera_, noticed that two of the numerous butterflies settled upon it did not fly away with their companions. Each of these he found to be in the clutches of a spider whose remarkable resemblance to the flower lay not only in its colour, but in the attitude it assumed. “Holding on to the flower-stalk by the two hinder pairs of legs, it extended the two long front pairs upwards and laterally. In this position it was scarcely possible to