The mystery seeds from last week that look like insects were indeed from yellow wood sorrel, Oxalis stricta.
There are a couple of other closely-related species of Oxalis that resemble O. stricta, and may be difficult to identify.
Native to North America, yellow wood sorrel can be considered to be a weed in certain nursery or turfgrass situations. Others may enjoy its delicate beauty, and consider it to be a wildflower.
In any case, don't you think it has unusual seeds?