Initial responses to substrates by naïve spiderlings: single and simultaneous choices

Whether foragers encounter resources sequentially (one at a time) or simultaneously has received relatively little explicit attention, given its potential importance for success. Here I evaluate the efficiency of naïve spiderlings Misumena vatia (Thomisidae) in exploiting hunting sites presented in these two ways. The spiderlings significantly preferred goldenrod (Solidago canadensis) inflorescences over aster (Aster umbellatus) inflorescences, both when these blooms were presented to them one at a time and simultaneously, if they were in physical contact with these blooms, a result that matched the numbers of prey these flowers attract. However, they accepted goldenrod significantly more frequently one at a time than in simultaneous presentations. Even when their substrates were then switched in a reciprocal cross, spiderlings favoured goldenrod over aster, although those moved from goldenrod to aster responded significantly more strongly (negatively) than did the reciprocal crosses. However, spiderlings did not distinguish between goldenrod and aster inflorescences simultaneously presented 10 cm away, and only two-thirds of them managed to recruit via lines to either of the flowers. They responded similarly to two-goldenrod inflorescences or two-aster inflorescences as to mixed goldenrod-aster pairs, and they recruited roughly half as often to a single inflorescence of either species as to pairs. At 50 cm, less than one-fifth recruited to the mixed substrate. Thus, the spiderlings first recruit to a site and then accept or reject it, a time-consuming activity. Costs in time for making simultaneous choices exceed those for one-at-a-time choices, due to their lower success rates in recruiting to the more profitable species.