314 AMERICAN SPIDERS AND THEIR SPINNINGWORK. 



development of these Tactile hairs. Immediately after hatching from the 

 eggs, Attus terebratus has none of these organs upon its tarsus or metatar- 

 sus, and only one upon the tibia. Lycosa saccata when first hatched has 

 not a single Tactile hair. After the second moult, however, both these 

 species acquire one hair upon the tarsus, two upon the metatarsus, and 

 two upon the tibia. Lycosa saccata when adult has four hairs upon the 

 tarsus, nine of such hairs on the metatarsus, and seven on the tibia. This 

 would seem to indicate that with the development of the spider, and thus 

 with the approach of need for sensation organs, Nature causes those organs 

 to appear. The young spider has no need of food, as it subsists upon the 

 nourishment provided by the mother in the egg. It is not until after its 

 first moult or two that Nature requires it to set up housekeeping for itself, 

 and capture its own prey. This is true of the Sedentaries. The Wander- 

 ers, at least some of them, live with the mother until the first moult has 

 been made. 



X. 



Are spiders mute ? The question is one of much interest, whether con- 

 sidered from the standpoint of the relation between the sexes, or 

 the number and nature of the senses. The amount of informa- 

 ^ on P ossesse< l u pon this subject is scarcely sufficient to warrant 

 a decided opinion, but such as I have will be presented. 

 At the outset, it may be suggested that, reasoning from analogy, we 

 would expect to find in spiders some mode of stridulation. The subking- 

 dom of Arthropoda, to which they belong, has at its head the Insecta, 

 among which are many genera whose species are characterized by their 

 power to stridulate. In illustration of this, any frequenter of our fields 

 and forests will recall the rolling drumming of the harvest fly or cicada, 

 which may be heard in vast and confusing notes when the seventeen year 

 locust, as it is popularly called (Cicada septendecim), makes one of its 

 periodical appearances, and covers the trees with hosts of insects. The 

 cheerful creaking of " the cricket on the hearth," which has passed into 

 our proverbs and poetry, is an example of stridulation. The shrilling of 

 the grasshopper, locust, and field cricket are other well known examples. 

 Professor Wood-Mason has discovered stridulating organs in the Phasmidax 1 

 These were seen in a species of Pterinoxylus, the stridulating organs being 

 fixed partly on the wings and partly on the tegmina, like the Orthopterous 

 vEdipoda described by Scudder. 2 



In these cases it has commonly been regarded, and is probably true, 

 that the stridulating instruments are exclusively possessed by the males, 

 and that the sound is in some way intended as a call to his mate. This 



1 Proceedings London Entomological Society, 1877, page xxix. 



2 American Naturalist, Vol. II., page 113. 



