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THE AMERICAN NATURALIST [Vol. XLII 



the female. But in certain other genera, as. for example, Argiope and 

 probably Nephila, the snares of the male are rudimentary, and do 

 not compare in perfection with those of the female. 



The immature males of the two species studied by 

 me construct perfect snares of the types of those of 

 their respective females. But the adult males of mar- 

 morea (no adult males of sclopetaria were examined) do 

 not spin snares at all but build nests near those of adult 

 females and 1 ive on the outskirts of the snares of the 

 latter; this was the case with all of the 23 mature males 

 found in the latter half of the month of August. 



Data on the snares of immature males are condensed 

 in the table already presented. The snares of orbs of 

 16 males of marm'orea in the penultimate instar show 

 the same average number of radii, a somewhat smaller 

 average number of spiral loops (41.3 to 48), and a 

 smaller average diameter (20.6 cm. in comparison with 

 23.4 cm. and 28. cm., as compared with snares of females 

 of this species in the penultimate instar and at maturity. 

 Data for the snares of 3 males in the antepenultimate 

 instar show somewhat lower averages. Those of 2 males 

 of sclopetaria in the penultimate instar, show, on com- 

 parison with adult females of this species, a slightly 

 greater average number of radii (20.5 to 19), a smaller 

 average of spiral turns (27 to 35.4), and a smaller average 

 diameter (25.4 cm. to 35.6 cm.). That is to say, males in 

 their penultimate instar construct fully as many radii as 

 do females in their penultimate or even ultimate instar, 

 but a smaller number of spiral turns and they make 

 smaller snares. But a male in his penultimate instar is 

 considerably smaller than a female of the same age, there- 

 fore in proportion to his size and weight his snare is quite 

 as complicated as that of the female and is in no sense 

 rudimentary. It would appear, accordingly, that the spin- 

 ning instinct, so far as the snare is concerned, is as perfect 

 m the male as in the female. He makes no web when ma- 

 ture because the sexual impulse completely overcomes the 

 desire for food, hence the instinct for snaring it, though 



