A problem that I have found in the insect rearing community is that we rearing specialists tend to view our domain as a strictly applied discipline. I try to counter this trend in my rearing courses. The problem is that as rearing specialists, we have a very narrow purpose in our job description: producing the target insect. The complexities of this job are so great that it’s easy to see why a busy rearing scientist would not find time to scan the literature looking for research findings that MAY be applicable to our target insect.

What I try to do in my courses is to make constant efforts to expand my own base of understanding and knowledge, and I further try to provide a base of information on the issues that give the students an appreciation for how seemingly disparate information may be of great value in understanding their insects in a rearing context.

One example of this is the recent discussions that I have posted on oxygen and carbon dioxide in our rearing systems. My experience of working with wax worms (larval Galleria mellonella) called my attention to the issue about whether or not the larvae were able to get sufficient O2 (and to void the CO2) that was produced by these crowded larvae (see Figure 1). Early in my waxworm rearing experiences, I learned that the larvae tend to aggregate and display high levels of activity, sometimes just pulsing back and forth in their silk tunnels. I saw this phenomenon in many different containers that I tested to optimise the rearing cages for my rearing system. From my observations, I became convinced that the larvae spend a great deal of their time and their silk-making resources in a quest for gas exchange.

Figure 1. Waxworm chimney. Note the silk structure constructed by the waxworms, giving them access to the gas-exchange opening in the rearing container.

This very applied question led me to investigate the gas exchange issues with G. mellonella larvae, and one of my current research topics is the determination of respiratory dynamics with various diets (low vs. high fat/ low vs. high carbohydrate diet mixtures). These studies have further led me to measure the O2 and CO2 in rearing containers where the waxworms crowd themselves in tight aggregations with high density populations. Naturally, the discovery that the waxworms were chronically under low O2 and high CO2 conditions led me to ask the questions about O2 and CO2 dynamics of other reared insects, especially the gregarious ones that we keep at high densities. This line of thinking led me to search the literature for various publications on the effects of O2 and CO2 stress (low oxygen and high carbon dioxide conditions). It was during this line of inquiry that I found the paper that I have been discussing from VandenBrooks et al. 2018 where the authors demonstrated the effects of hypoxia manifesting itself with enrichment of tracheoles and mitochondria. This very basic science discovery may have far-reaching implications for insect rearing where the practical (applied) issue of quality control of our insects can be directly related to availability of O2 and dispensing of CO2.

More about these relationships in further posts, but let me re-emphasize the importance of being flexible minded about what is “mere basic science” vs. what has very practical implications in our rearing systems.