HARVEST-SPIDERS 145 



usually white, devoid of sculpturing and adhere loosely together. 

 Their number varies from over 200 in Odiellus spinosus according 

 to Sankey (1949b) and 275 in Platybunus pinetorum (Stipperberger, 

 1928) to 400 to 600 in Phalangium opilio according to Gueutal 

 (1944). Holm (1947) found that Opilio parietinus laid from 20 to 60 

 eggs at 20° C, and that there was no further development after an 

 early blastoderm stage unless the eggs were transferred to a refrig- 

 erator, where they were kept at 6° C for two weeks and then, for a 

 further week, at - 6° C. In Leiobunum blackwalli, however, the 

 percentage of eggs hatching was not significantly higher after cold 

 treatment according to Todd (1949). 



A faint mottling indicates the onset of development; the eyes 

 appear at one pole and just before hatching the body segments and 

 limbs can be seen neatly tucked away inside the egg. Hatching is a 

 quick process, the young breaking the egg membrane by means of 

 a powerful egg-tooth in front of the ocular tubercle. European Pal- 

 patores are about 1 mm in length on emergence. The newly 

 hatched young resemble the adults in general, but are distinguished 

 by the absence of a number of detailed characters which are grad- 

 ually assumed with each moult. The first of these occurs almost 

 immediately after eclosion and is followed by six or seven others at 

 intervals of about ten days extending over a period of six to nine 

 months. The young are at first soft-bodied and sluggish in their 

 movements but there is a progressive hardening of the integument 

 with each ecdysis. In those Laniatores and Palpatores which have 

 numerous tarsal segments in the mature forms, the number is far 

 fewer in the young stages and increases as they grow older. 



Where known, the soft-skinned, delicate eggs of the TroguHdae 

 are laid in the shells of snails in which they are sealed by a pro- 

 tective membrane secreted by the ovipositor of the female. The 

 number varies from one to eight in each batch, but as many as 25 

 eggs may be laid by a single female during the year. Maximum 

 activity takes place in the spring and autumn but eggs are produced 

 during every month except December and January. The duration 

 of ontogeny depends upon the season at which the eggs are laid, 

 and development is slow between October and March, coming 

 almost to a standstill between November and February, but in the 

 summer months it lasts five to eight weeks. Post-embryonic devel- 



K S.S.C.M. 



