446 Thos. H. Montgo?nery, Jr. 



infertile, which renders unhkely the occurrence of parthenogen- 

 esis in this species.^ 



4 When we compare the male ratios of individual cocoons 

 given in the most right hand column of Table I no constant relation 

 is found between this ratio and the position of a particular cocoon 

 within a series. The ratio may or may not be markedly different 

 in immediately successive cocoons as well as in cocoons at the 

 extremes of the particular series. The male ratio does not reg- 

 ularly increase from the first to the last cocoon, nor does it reg- 

 ularly decrease. Yet it will be noticed that of the twelve larger 

 series of cocoons of Table I, in seven of them the first made cocoon 

 of the series shows the highest male ratio (series 2000, 2003, 2008, 

 2013, 2014, 2020, 2022). 



2 OBSERVATIONS ON OTHER ARANEADS 



The only observer who has furnished detailed data upon the 

 sexual relations in spiders is Doumerc." In the autumn of 1839 

 he captured a mature female of Theridion triangulifer and liber- 

 ated it in a room where it formed a web in a window frame. On 

 April 23 following it made a first cocoon from which only males 

 emerged and on May 10 a second cocoon from which hatched 

 only males. On June 16 she was impregnated by a male, on 

 June 26 made a third cocoon from which only females emerged 

 and on June 28 a fourth cocoon from which came out only males. 

 Doumerc does not state how he distinguished the sexes of these 

 spiderlings; and for such "unisexuelliparous" species he con- 

 cludes that there are two uteri, one for males and the other for 

 females, and that oviposition does not take place from both at 

 the same time. 



In collections adult females are usually more numerous than 

 adult males, due simply to the fact that males in their mature 

 condition are usually short-Hved. But during the mating season 

 males are more abundant in most species, certainly among the 



5 Compare Montgomery: On parthenogenesis in spiders. Biol. Bull., 1907. 



6 Notice sur les Cocons a pontes unisexuellipares de I'Araneide Theridon triangulifer, Walck. Ann. 

 Soc. Entom., France. 9, 1840. 



