The pH of the insect gut is variable, and has significant influence on the actions of enzymes secreted in the midgut, and solubility of the food. Different enzymes function optimally at different pH levels. Though the gut tends to be slightly acidic in most species (about pH 4–6), the gut pH is related to host plant chemistry. Insects that feed on trees, which typically possess high levels of tannins, have higher pH levels, around 8.6, apparently because this reduces the effects of ingested tannins. The hindgut regions of insects ingesting cellulose, such as termites and crickets, tend to be acidic due to anaerobic fermentation of glucose derived from cellulose digestion.