342 MR. R. I. POCOCK ON THE [ Apr. 21, 
the belief in the existence of a ‘ gossamer’ spider which is supposed 
to be the cause of the fine threads which fall from the air and 
carpet the fields with silk at certain times of the year. It is now 
known that the ‘gossamer’ spider is a mythical species, and that 
species of the most diverse habits belonging to widely different 
families are responsible for the floatmg threads. The habit is 
practised alike, and, so far as is known, to an equal extent, by 
snare-spinning forms belonging to the Argiopidee and Theridiide, 
by hunting-spiders like the Lycoside and Attide, or by sedentary 
species that lurk in flowers, like the Thomiside. 
That this method of locomotion may considerably influence the 
distribution of spiders may be inferred from the fact that cobwebs 
thrown out in this way, and affording support to little spiders, 
have been found at the tops of our highest buildings, and have 
become entangled in the rigging of ships 200 miles from land. 
There are reasons for thinking, however, that the habit 1s for 
the most part restricted to phanerozoic diurnal species, namely, 
those that hunt their prey or spin their webs in the open; and 
that cryptozoic forms, that live in burrows or under stones or logs 
of wood, and that are for the most part nocturnal, do not indulge 
in it’. 
Clearly, therefore, these eryptozoic groups, in which the restric- 
tions to dispersal are presumably the same as in other terrestrial 
animals which can neither fly nor swim to any distance, have more 
value for the establishment of geographical areas than those species 
with powers of dispersal analogous to flight. 
Owing to the relatively large size and great weight of the newly 
hatched | young of the Mygalomory phee, coupled with the reduction 
in the number of spinning- appendages and the greater simplicity 
of the silk-glands, it seems probable that aer ial sailing is not 
practised to any great extent by the members of this: suborder 2. 
Especially true will this be of the Aviculartide, a family which 
contains the largest spiders known of this or any other epoch, 
with newly-born young rivalling or excelling in size the adults of 
many species of the Arachnomorphe. 
Consideration of these facts, coupled with the impossibility of 
dealing in detail, in one paper, with the distribution of all the 
genera of the Aranez, has led to the selection of the Mygalomorphee 
as the fittest group to illustrate the geographical distribution of 
Spiders in general. 
1 Simon states that the Spider-fauna of the Sandwich Islands is composed wholly 
of species of the former category, with the exception of some few forms which appear 
to owe their presence in that Archipelago to human ageney (‘Fauna Hawaiiensis,’ 
sranee; 1902). 
2 The young of the only known British representative of this group, namely 
Atypus, one of the smallest types of Mygalomorphe, have been seen to scatter over 
small areas by this method of tray elling (EB. BENE Tr. Ent. Soc. 1885). 
In this connection it is instructive to remark that Atypus has a wider distribution 
than any other known genus of the suborder, ranging from Ireland and Algeria to 
Japan and over the Hastern (? the Western) ‘States of North America, that is to say 
ene the Northern hemisphere from the eastern to the western shores of the 
tlantic. 
