Some months ago I walked into a pet store and saw a glass tank with mealworms eating dry cat food. Since dry cat food comes in nuggets that allows you to easily recover the leftovers this gave me an idea for new activity. The rule of thumb for productivity/energy recovery up each link of the trophic pyramid is around 10%. The biomass recovery I got with with my mealworms was around 20% (based on dry weight). It is higher than the rule of thumb because I was raising them during their period of rapid growth and feeding them a high protein diet (cat food). It would not have been practical for me to feed them grains because it would have been too difficult to recover all the left overs. At any rate, the reason for this high feed conversion is addressed in the questions at the end of the activity. You do not have to kill your worms because I provide a conversion factor for dry weight of worms. The feed to live mass conversion ratio was 2:1. This is comparable to that of farmed fish, which is not surprising because both fish and mealworms are cold-blooded and farmed fish are usually given a high protein diet. In effect, this activity addresses two important topics, the trophic pyramid and livestock feed conversion. It took me only ten days to do the experiment, but since you need to care for the worms every day this might not be practical if you are teaching a class that meets less than 5 days a week. I do not rule out posting a video on this, but it you want the write-up you will have to purchase the upcoming edition of my lab manual.
This blog was originally created in January 2013 to serve as a means for providing updates on science activities from the environmental science lab manual Ecology, Development, and Sustainability. I have now expanded its purpose to include other items of interest to science teachers.
