::::::::::Hi Pilcha...I didn't understand that you wanted to include this into the illustration. I don't think it is really necessary to get the basic point across. That illustration is a remake of a simpler illustration that was in  Kormondy's textbook Kormondy, E. J. (1996). Concepts of ecology (4th ed.). New Jersey: Prentice-Hall. pp. 559. ISBN 0134781163. and the leakage wasn't illustrated in that image either. You can see an energy flow diagram in the free online nature scitables article on secondary production  - they used a snail - I redrafted this image using a frog in the energy flow section. This is a replica of a stylized energy flow image that Eugene P. Odum used in his publications (e.g., ). Odum placed an E just below the outflow that he considered to be part of a production - even though it is waste, it is productive waste: "E refers to assimilated organic matter which is excreted or secreted (e.g., simple sugars, amino acides, urea, mucus, etc.). This "leakage" of organic matter, often in dissolved or gasseous form, may be appreciable but is often ignored because it is hard to measure." If you look at page 227 in the following article  - you can see how Howard T. Odum (Eugene's brother) - illustrated heat sinks, which is the energy dispersed into heat at each transformation. You could illustrate a heat sink stemming off each trophic species (node) - but it might clutter the image. I'll leave it up to you.