II4 Origin of the Araneidal Fauna of. Yorkshire. 
moisture and varying temperature, the threads descend, 
and reinforced by fragments of webs blown from their moorings 
by gusts of wind form the familiar ‘ gossamer showers.’ 
Among those specially addicted to the practice are adults of 
the smaller and less weighty kinds, species of the genera 
Erigone, Savignia, Dicymbium and Cdothorax, and in spring 
and autumn the young of many others. Darwin in the‘ Voyage 
of the Beagle,’ Chapter VII. mentions that on several occasions 
thousands of a small spider of the same species but of both 
sexes and all ages settled on board the ship when 60 miles from 
land and could therefore have only done so after a lengthy 
aerial flight. In Chapter I. of the same work he states that 
spiders are among the earliest inhabitants on newly formed 
oceanic land, a striking testimony to their powers of dissemina- 
tion. Mr. W. H. Hudson, in his ‘ Naturalist in La Plata,’ 
also relates a remarkable instance of aerial dispersal on a 
gigantic scale which he witnessed near Buenos Ayres. In this 
case the filaments of a countless number of spiders, represent- 
atives of four different species awaiting more favourable 
meteorological conditions to continue their journey, were in 
such abundance as almost to hide the grass and thistles beneath 
them and formed a continuous band twenty yards wide which 
was followed for two miles without finding the end. 
The interchange of natural vegetable productions obviously 
furnishes an easy and simple means for the accidental trans- 
ference from place to place on the earth’s surface of even soft 
bodied creatures like spiders which are, moreover, tenacious of 
life and able to endure long fasts. Their eggs may also thus be 
carried, or if the trees. in the cracks and beneath the bark of 
which many kinds conceal their egg sacs, should become derelict, 
they are often drifted a considerable distance before again 
reaching land. Instances of living spiders of various species 
being brought to this country from foreign lands in consign- 
ments of bananas, oranges, logwood, etc., are now frequent and 
familiar. Examples of the kind may be frequently found in 
museums, and at any seaport with foreign trade, collections of 
exotics, some of them new to science, may now be made. 
Circumstances do not favour these aliens, and as a rule they 
either get no chance to establish themselves or fail to find a 
suitable habitat. Some few which are natives of a warmer 
climate are known to have done so, having found congenial 
shelter in greenhouses, hothouses and nurseries and are believed 
not only to have been introduced but also disseminated in such 
places with exotic plants. Two of these have been met with in 
Yorkshire—one, Theridion tepidariorum C. L. Koch is now 
very common in most British greenhouses, and the other, 
Hasarius adansonii Say., very much rarer in hothouses. 
(To be continued). 
Naturalist, 
