Comments about salt or mineral mixtures in insect diets (Beck salts, Wesson salts)
Rearing personnel use in their diets components that are specified in the literature, and quite often we use materials that have authors’ names associated with them (such as Wesson salts, Beck salts, Vanderzant vitamins, etc.) I have been working on a diet for spotted lantern fly, which is reported to be a phloem sap feeder, and in keeping with this assumption, I wanted to use a derivation of the aphid diet reported by Mittler and Dadd (1962) with modifications by various authors from Stanley Beck’s laboratory, such as the paper by Retnakaran, A. and S. D. Beck. 1967. Aspects of mineral nutrition of the pea aphid Acyrthosiphon pisum (Harris). J. Nutrition, 92: 43-52. This paper provides a salt mixture that was used in experiments on pea aphid nutrition, and the authors concluded that an imbalance in the ratio of calcium and phosphate caused failure of the aphids to grow and thrive. I wanted to try a salt mixture widely reported on insect diets provided commercially as a salt/mineral mixture called “Beck salts.” However, being aware of the importance of mineral characteristics, including concentrations and molecular species of salts, I was trying to get information from one of the suppliers who shall remain unnamed for this blog article. I asked the supplier for the details about types of minerals and their concentrations, and I got a response that provided this list:
Beck Salt (Mineral) Mixture (I have withheld the supplier’s name for the sake of discretion).
Calcium Phosphate, Tribasic
Calcium Phosphate, Monobasic
Potassium Phosphate, Dibasic
Potassium Phosphate, Monobasic
The list of components told me that the mixture contains sodium, iron, manganese, zinc, copper, calcium, magnesium, and their counter ions such as chloride, sulfate, acetate, and phosphate, but it tells me nothing of the concentrations. I wrote back to the supplier, including my comments on the importance of the relative amounts of these minerals (salts) in the “Beck salts” that they supply, and I included a reprint of the paper by Retnakaran and Beck 1967, but I never got an answer to the question about the concentrations of each component in the list that I copied above. Evidently, the supplier considers the question of proportions of the mixture of insufficient importance to provide the answer to my question. In my inquiry, I conceded that if the mixture was proprietary, then it should not be referenced as a “Beck salts” mixture and that if the mixture was actually made by some other supply source, that supplier should be willing to fully describe their product. I will write more in a future blog article about the nature of salts and their counter-ions and other characteristics, but clearly for the present article let me simply emphasize the importance of diet and rearing professionals knowing and understanding the complete nature of the mixtures that they use in diets.
What I have discussed here is a very specific example of how people who rear insects and often people who supply the rearing personnel with diets, diet components, or other rearing materials do not sufficiently take seriously the importance of what may seem to be minor matters. I have heard many well-meaning rearing professionals express shock and dismay that suppliers may make changes in the rearing components they depend upon for quality. Another assumption commonly held by rearing personnel is that there is an exact set of characteristics of diet or other rearing system components, and it is assumed that when we buy a brand of agar, salt mixture, wheat germ, or other material there is a sameness from one batch to another. This assumption of sameness or “standardness” does not always hold up, and in my nearly 4 decades of rearing experience, I have seen dozens and dozens of instances when an otherwise stable rearing system crashed or manifested problems in the quality and quantity of their insects.
If my posts and other efforts to help us improve rearing raise the consciousness of rearing personnel about the importance of careful adherence to process control standards, I will have done something of value to rearing professionals and their stakeholders.