Insect capturing leaves are thought to give carnivorous bog plants a supplementary source of what?

1. Carnivorous plants such as the Venus flytrap and the pitcher plant grow in bogs. 2. The soil of those bogs is low in nitrogen. 3. In these plants the leaves are modified to capture insects. 4. Those insect capturing leaves may have evolved to supply a supplementary source of much needed nitrogen. 5. Potassium, phosphorus and magnesium are all essential nutrients, but the bog shortage named here is nitrogen. 6. This is why the adaptation is nutritional rather than a defence against being eaten. _Source: OpenStax Biology (1st ed., CC BY 4.0), Ch 30 "Plant Form and Physiology", section 30.4 Leaves_