546 OPILIONES. 
Order OPILIONES. 
The members of this order, known also as the “ Phalangidea,” or by the trivial 
name of “Harvestmen,” must have taken their origin ages ago, even before the 
Carboniferous period, together with the ancestors of the Scorpiones, Pedipalpi, Acaridea, 
Chernetidea, &c., springing from a vast congeries of more or less problematic forms 
to which the name AZropneustea has been applied. It is probable that all the present 
existing Land-Arachnids diverged from the still earlier congeries of water-breathing 
forms, Hydropneustea, represented by the fossil Gigantostraca and Limuloids, and in 
recent and present times by the only surviving forms, Limulus and the Pantopods. 
The period of their origination must, at any rate, have preceded the appearance 
during the Carboniferous epoch of the air-breathing scorpion, Anthracoscorpius. It 
is probable that the specialization began during the still earlier Silurian times, 
since in this period there existed an Arachnid which is a true scorpion in every 
sense, except that it has apparently no trace of air-breathing lung-sacs. It cannot at 
present be definitely decided whether these Silurian scorpions were “ air-breathers ” or 
‘“‘ water-breathers,” but itis probable that about this period of geological history modern 
Land-Arachnids, and with them the Opiliones, became specialized from water-breathing 
ancestors, since undeniable Opilionids, represented by Hophrynus and various other 
genera, existed in Carboniferous times. 
The habits of the Opiliones are much simpler than those of the Araneidea, for 
although, like them, they are carnivorous, they make no web for the ensnaring of their 
prey, and the production and care of their offspring resolves itself into laying their 
eggs in convenient chinks and crevices, where the female leaves them, taking no 
further interest in their welfare. 
The various species differ remarkably in structural character from the true spiders, 
although they approach more closely the Rhynchostomi or Acaridea in this respect. 
The “ prosoma ” and “‘opisthosoma,” which are distinctly separated by a narrow pedicle 
in all the Araneidea into two main portions,—the carapace and abdomen—are in the 
Opiliones and Acaridea fused together. The traces of the original segmentation of the 
opisthosoma are still in strong evidence, the terminal four segments being even now 
free and unfused amongst the former, but in the Acaridea they have become entirely 
obsolete. The ‘“ Harvestmen,’ as well as the “Mites” and “Ticks,” breathe by 
means of stigmata communicating with a system of tracheal tubes, the openings in 
the case of the Opiliones being two in number, situated on the third opisthosomatic 
segment, behind the coxe of the fourth pair of legs, there being also spiracles on the 
tibiee of the legs. 
The method of the fertilization by the male of the ova of the female differs entirely 
from that which obtains amongst the true spiders. Whereas in the latter case no 
