I want an explanation for the high concentration of Zn in the body of control insects collected from clear environment (control) having Zn fairly allied with the established standard level.
I assume that the insects are confined and could not have migrated into your experiment. I assume that the insects are reared in a clean environment without the possibility of contamination. I assume that there is no possibility that the experiment could be sabotaged by an unhappy worker in your department or another. I assume that the water source does not carry elevated zinc levels that might come from plumbing or another source. I assume that no insecticide or fungicide that was used also contained Zn. I assume that the fertilizer used for growing plants had a normal level of Zn. I assume that human error has been eliminated in all its forms.
With all those options out of the way, what an interesting finding. Does the plant bio-accumulate Zn as a defensive mechanism against herbivory?
There is some research using Sr isotopes to study food webs. The Sr isotope is applied to the soil, taken up by the plant, which is eaten by the herbivore, and ends up in the predators. There is no reason other elements would not follow the same path if given the chance.