May one move a bowl of fruit fly poison on Shabbos from one corner of the counter to another to be closer to the flies?

That would be similar to placing a trap on Shabbos which is forbidden.

Additionally, the trap itself is Muktza and can not be moved for this purpose.

ראה שו”ע אדה”ז שטז, ו. והוי ככלי שמלאכתו לאיסור.