Author: Allen (Page 1 of 4)

Allen Carson Cohen has been a researcher and teacher in insect rearing and related disciplines for more than 40 years. He has published books and more than 100 papers on insect rearing and related topics. He is dedicated to helping change insect rearing into a more scientifically-based practice and to help rearing specialists become more properly valued.

Insect rearing education: basic vs. applied research in relation to rearing systems (Allen Carson Cohen)

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.

Critical thinking in our insect rearing courses (Allen Carson Cohen)

Figure 1. Complexities and interactions in insect rearing systems. This diagram is my effort to show some of the complexities that underlie insect rearing systems, including the image in the lower left showing the “Fly Room” used by T. H. Morgan and his now famous assistants. I have also included a gut of a lacewing adult, and the microbes from the gut of a termite (centre left)

In all my courses, I try to emphasise how we can use critical thinking and basic science to better understand all the components in our rearing systems and how these components interact to make the systems function. I designed the diagram to be complex-looking to emphasise the many, many intricacies of rearing systems, especially the many kinds of interactions between the numerous “moving parts.”

In this diagram, I tried to represent how we can zoom-in on facets of the rearing system so that we can understand them in a piecemeal fashion, which leads to an overall understanding. Philosophers of science might call this going from the specific to the general, which is characteristic of inductive reasoning. My approach to rearing systems is to explore relationships inductively to arrive at generalisations, and then use the generalisations to help us better understand and predict the specifics (= deductive thinking). This kind of thinking is not new to me; it was approached by such famous scientists as Claude Bernard (1813-1878) and the person who suggested the concept milieu interieur, which is the basis of our concept of homeostasis.

In the diagram in Figure 1, a relationship between metabolic rate–oxygen–tracheal diameter is shown. This concept is discussed in reference to a paper that I cited from VandenBrooks et al. 2018 who showed that in response to lower than normal atmospheric oxygen levels, Drosophila melanogaster developed larger, more complex tracheal systems (tracheole branching, diameter, number) and more mitochondria while in higher than normal O2 atmospheres, the insects showed the opposite trends. In the post where I first raised this issue, I suggested that this phenomenon could be taking place in other insects, and I further suggested that under rearing conditions where the O2 levels were not as low as the experimental values used by VandenBrooks et al., the same types of changes in respiratory organs and organelles may follow the same trend, but possibly to a lesser extent. I further provided data from some of my rearing observations where I showed that indeed, under commonly found rearing conditions, insects displayed lowered O2 and elevated CO2, though my observations did not find such low levels as those imposed by the VandenBrooks team.

This is where my point about critical thinking comes in. A published study demonstrated that a series of very dramatic changes took place in one insect species’ respiratory system morphology and ultrastructure. Does this mean that such changes take place in other insects (such as my wax worms or somewhat crowded painted lady butterflies)? The finding with D. melanogaster does not establish that the types of changes discussed here take place in my subjects or in the other insects that are routinely reared. Also, the extent of the hypoxia (low oxygen tension) does not necessarily extend to lesser hypoxic conditions. An important part of the critical thinking that I am encouraging in my courses is that rearing personnel are well-served to take what we know about insect physiology, biochemistry, genetics, ecology, microbial relations, etc. and consider how such basic science knowledge MAY apply to their insects in their rearing systems.

This approach encourages inquiry into the possibility that our wax worm larvae, Medfly larvae, naval orange worm larvae, or black soldier fly larvae are crowded enough that 1) the O2 in their rearing container is chronically and substantially under the 21% (closer to 20.85%) of outside air? 2) the response of the respiratory structures is an increase in tracheole structures and mitochondria is to increase significantly over that found in “normal atmospheres”)? 3) if there are changes in the tracheoles and mitochondria, does this affect the fitness or quality of the insects that we are rearing? and 4) does the change in fitness or quality adversely affect the purpose of our rearing these insects? Other accessory questions could be 1) does the diversion of biomass to tracheoles and mitochondria come at the expense of other structures or fitness characteristics (wing size, cuticle resistance to microbial penetration, muscle activity potential)? 2) If the oxygen (and CO2) levels are abnormal due to the crowding and/or the gas exchange between the rearing containers and the rearing room air, is it possible that other density-related factors are askew (excess nitrogenous waste, enhanced microbial growth, deteriorated diet components)?

Of course, no rearing facility has the capacity to do all the inquiries that would be needed to answer all these (and MANY MORE) questions, but doing some critical thinking and data based inquiry can be derived from this type of thinking and respecting the complexity of the insects in our rearing systems!

More about this in posts and pages to come!

More rearing systems as ecological niches (introducing ‘fitness,’ ‘quality,’ and ‘homeostasis’ as rearing concepts) (Allen Carson Cohen)

Figure 1. Drosophila melanogaster larva and three adults feeding on a yeast-based artificial diet. Note the red material in the gut of the larva, which is diet dyed with Congo Red to help us visualize the pH of the gut.

In a recent post, I discussed the components of rearing systems that comprise the ecological niche setting. In that post, I provided a table from my book on rearing systems, and this table included 22 parameters which are present in the insects’ natural ecological niche and which must be provided in the artificial niche. For example, the table includes what I have called the “starter insects’ genetic characteristics” as well as food, waste product accommodations, gas exchange, moisture exchange, light relations, and so on.

In my experience with scores of rearing systems, small and large scale, many of these “niche components” are often neglected or underestimated by rearing personnel. Because most of us who require insects for research or other purposes are concerned only with the practical matter of having the insects available for our purposes, we do not bother to scrutinise the various features of how well our rearing system satisfies the fulfilment of the niche requirements. This is to say, we do not examine the character of the light relations (optimal photo-period, optimal intensity, and optimal light qualities or wavelengths). Likewise, we do not pay much (or any) attention to the microbial profile of our insects; and with few exceptions, we take at face value the microbial relations that are taking place in our insects. If we produce successive generations of Drosophila, for example, to meet our genetics investigations, we do not ask about the microbial profile of the insects’ guts or their environmental microbial associations. If the flies reproduce in their rearing containers, we do not ask if the gas exchange is optimal or if there is a stress imposed on our flies by excessive buildup of CO2 or by O2 deficits. Despite the fact that some researchers such as the VandenBrooks team have shown that O2 deficits can lead to dramatic changes in the respiratory system’s ultrastructure (increased tracheal branching and diameters as well as increased mitochondria associated with hypoxic conditions).

We rearing specialists and users of reared insects too often make the mistake of taking at face value the health and well-being (FITNESS) of our insects. Another way of regarding this fitness is as the QUALITY of our insects, and this is directly associated with the physiological concept of HOMEOSTASIS.

Insect rearing systems are engineered ecological niches

Figure 1. Cells in a 32-cell tray being used to rear Heliothis virescens larvae.

The above image (Figure 1) shows pre-pupal larvae being reared on a wheat germ diet derived from the Yamamoto 1969 tobacco hornworm diet. In this figure, a few of the “moving parts” of the rearing system are depicted, the insect, the diet, frass, and slits in lidding for gas exchange. There is also an indication that microbes are ever-present in rearing systems, within the insects, in the frass, and other parts of the rearing system. Still more features are present in this rearing sub-system, including the environmental conditions such as temperature, humidity, light qualities (including photo-phases, light intensity, and light quality). Sounds and odors also help comprise the insects’ environment as are container configuration and population density (number of individuals per unit of container volume). Many examples of the potential complexity and intricacy are prominent features of rearing systems that are helpful to understand; take microbes, for example.

Various microbial interactions are possible in the rearing system.

Figure 2. Some kinds of microbial interactions in insect rearing systems.

In Figure 2, the greenish background is a colony of fungi that grew on an insect diet where the moisture content was too high. In the upper foreground, the black and white image shows the partially-dissected gut of a lacewing adult with the gut contents shown to include yeast which are part of the rearing diet of the lacewings and which also reside in the insect’s specialised, diverticulum-based gut where the yeast thrive as symbionts with the host adult. The lower left picture shows whitefly larvae with their characteristic mycetomes (paired reddish structures), and the image on the lower right shows microbial inhabitants of the gut of termites. Besides these relationships of insects with symbionts (which are mutualists with the insects) and contaminants, there are also possible relationships with pathogenic microbes. ALL of these relationships must be understood to help keep our insects thriving (unstressed and displaying homeostasis) in the colonies that we house in our rearing systems. More on this in the next post. Please note the table (taken from Cohen 2021: Design, Operation, and Control of Insect Rearing Systems, CRC Press). I will comment further on this table in the next post.

Figure 6.1. Simplified Niche Parameters Expressed in an N-Dimensional Hypervolume. Figure 6.1 depicts the idea that there are many facets of niches, represented as intersecting or overlapping vectors. The intersections represent the concept that niche parameters are interactive.

Niche ParametersRange of Niche Parameters
Starter Insects’ Genetic CharacteristicsFull genome characteristics, including genetic diversity
Food/dietsType & amount of food eaten
Waste productsNitrogenous wastes, moisture, undigested food
Gas exchangeCO2 output, Ointake
Moisture exchangeWater ingested, evaporatedInsects’ effects on humidity in rearing container through cuticular, respiratory, and fecal water loss, cuticular and respiratory water loss, osmotic values of water in aquatic systems
Light relationsEffects of photoperiod, light intensity, and light quality (including possible other electromagnetic spectrum wavelengths such as UV and IR
Microbial relationsBeneficial microbes, pathogens, commensals, etc.
Population densityHow many individuals/unit of rearing space?
Population dynamicsGregarious vs. solitary, agonistic behavior, competition, group digestion, group thermal regulation, etc.
Effects on substrate (biting, lidding, etc.)Degrade container by biting holes, webbing to “manage” frass, digging and conditioning soil, pH of water for aquatics, etc.
Mating conditionsRatios of ♂/ ♀; number of adults, environmental conditions, space for courtship, pheromone plumes, etc.
Oviposition conditionsMaterials for egg inserters, conduce conditions for egg-laying & egg development/egg hatch
Populations of competitors (e.g. mites and psocids)Often on plants used to rear insects and sometimes on artificial diets (see text discussion for details)
Populations of parasites/predatorsThe large biomass and populations of mass-reared insects offer a target for cryptic parasitoids and predators
Thermal relationsTemperature tolerances and optima influence the success or reared insects and further influence susceptibility to microbial attacks
Silk utilization/dynamicsMultifunctional uses of silk are discussed in the text
Effects of other (than silk) secretions: extra-oral fluidse.g., glandular secretions, oral/salivary secretions, modifying nutritional quality and bioavailability 
Scales (as dust hazards, etc.)Potential for microbial transfers, influencing gas exchange, debris
Waste productsNitrogenous wastes as toxins, substrates for microbial growth, blocking normal food ingestion by clutter, etc.
Gas exchangeRange of O2 uptake and CO2output on cultured insects, dispersal of O2 and CO2 in containers
Insectary soundscape/vibration-scapeFactors that interfere with auditory communication (stray noise) or vibrations that produce stress or induce excessive responses
Factors involved in oxidative stressFactors in diet or environment that generate free radicals or reactive oxidative species in insects

Table 6.1. Niche parameters in rearing systems.

More on design of experiments in insect rearing systems (by Allen Carson Cohen)

I have become comfortable with the JMP (from SAS) tools for using design of experiments (DOE). I share here some compelling statements from the JMP website:


What is design of experiments?

“Design of experiments (DOE) is a systematic, efficient method that enables scientists and engineers to study the relationship between multiple input variables (aka factors) and key output variables (aka responses). It is a structured approach for collecting data and making discoveries.

When to use DOE?

  • To determine whether a factor, or a collection of factors, has an effect on the response.
  • To determine whether factors interact in their effect on the response.
  • To model the behavior of the response as a function of the factors.
  • To Optimize the response.

“Ronald Fisher first introduced four enduring principles of DOE in 1926: the factorial principle, randomisation, replication and blocking. Generating and analysing these designs relied primarily on hand calculation in the past; until recently practitioners started using computer-generated designs for a more effective and efficient DOE.”

The quotation from the stated website (from JMP) gives the basis of the arguments that I am asserting about why DOE is such a valuable tool for insect rearing personnel. First, the idea of studying the relationships between multiple factors should appeal to every rearing specialist. When we put our insects into a rearing system and provide them with artificial diets, we should wonder how the diet components affect the insect and how they affect one-another. For example, how does the pH of the diet relate to solubility of a protein supplement such as casein? Furthermore, how does the pH affect solubility of salt mixtures such as Wesson salts? A little inquiry about casein (which should more properly be called “caseins” because there are several milk proteins that are indicated by the term “casein”) shows that this protein is very hard to dissolve at near neutral pH levels. Therefore, unless we make special efforts to dissolve casein (such as pre-dissolution in basic solutions), this important protein is likely to form pockets within the diet where it is non-homogeneously distributed. The casein-rich vs. casein-poor pockets contribute to the problem of non-uniformity, which leads to serious differences in growth and development rates of larvae that are otherwise similar in age and genetic composition. The same type of non-homogeneity applies to dissolution and distribution of salt mixtures. I have shown (Cohen 2015) that Wesson salts are virtually non-soluble unless they are dissolved in a low pH solution. That helps explain some of the positive effects of using diets that are on the acidic side, rather than neutral. Further analysis helps us understand that the texture of the diet, in terms of firmness or gel strength, is enhanced by the presence of salt mixtures where Wesson and Beck salts have an enhancing effect on the gel strength of agar, carrageenan, or other hydrocolloid gels (Cohen unpublished data).

Figure 1. Diet Factor Interactions

In Figure 1, I have tried to suggest some of the complicated interactions that are present in an insect diet. The lesson here is that using DOE-based investigations, we can begin to dissect the components of our rearing systems to help us understand the ways that rearing factors affect the nature and success of our rearing systems. The whole thrust of this approach is to turn the “black boxes” that describe our rearing systems into more transparent and logical processes.

More about this in future postings!

Design of experiments in rearing systems (by Allen Carson Cohen)

Currently, in all my classes, I use design of experiments (DOE) to help us better understand the factors that are most important in insect rearing systems. I originally became aware of the applications of DOE through a criticism of my statements about using one factor at a time for diet development in my book on insect diets (Cohen 2004). The criticism came from Dr. Steve Lapointe et al. (Lapointe, S. L., T. J. Evens, and R. P. Niedz. 2008. Insect diets as mixtures: Optimization for a polyphagous weevil. Journal of Insect Physiology. 54: 1157-1167.) I was initially dismayed at the criticism of my conventional (and outdated) thinking that we could only use one variable (one factor) at a time in a good scientific experiment. Once I got over the ego-deflation of having a blatantly narrow statement in my book, I set-out to learn how multiple factor experiments could be far more telling about the nature of our diets and other rearing system components.

As a start in my new-found application of DOE, I included this more sophisticated approach in the 2nd edition of my Insect Diets: Science and Technology, but I still had a steep learning curve. After years of effort to learn how to use the JMP approaches to DOE, I have reached a point where I routinely use various DOE tools (response surface designs, full-factorial designs, mixture designs, and Taguchi designs–all of which have their own specific applications). I have included extensive tutorials on using JMP’s system of DOE-based programs in my newest book, Design, Operation, and Control of Insect Rearing Systems (2021, CRC Press).

I want to make a special point about using JMP’s DOE: I am a physiologist, NOT A STATISTICIAN. Despite my trying to learn how to apply DOE, once I learned how powerful it could be in helping me understand the science behind insect rearing system dynamics, it was still a steep learning curve for me. I realize that most of my fellow rearing professionals are NOT statisticians either, and that is why I believe the JMP system’s DOE is so helpful. It allows people like me to ease their way into the very powerful statistical programs that can be so helpful in understanding what is going on in our rearing systems. The following mini-case study helps illustrate this point:

Figure 1. A test diet experiment in JMP DOE applied to optimization of painted lady diets.

In Figure 1, I present a test that I did with painted lady butterflies (Vanessa cardui). In this test, I was asking the questions about the efficacy of sweet potato flour, rice bran extract, citric acid, and three types of protein (casein, soy, and dairy whey). The table in Figure 1 shows that I used two levels of sweet potato flour, two of rice bran extract, and two of citric acid while I provided casein, soy, or whey proteins. This full-factorial design required that I make up and evaluate 24 different diets (all of which had the same proportions of the other diet components not shown here). In the last two columns (on the right), the responses of total biomass per rearing unit and mean weight of individuals are presented. Feeding these data into the JMP system resulted in a complete statistical analysis of the experiment, including this convenient summary of the outcomes:

Figure 2. JMP’s Prediction Profiler of data from table in Figure 1.

In Figure 2, the summary of the experiment is shown in terms of the total biomass that was derived from insects on the 24 different diets. This graphic representation helps us see clearly that the higher amount of sweet potato flour (10 g) gave superior results to the 5 g versions. The rice bran extract did not contribute substantially in either the 3 g or the 6 g versions. The higher level of citric acid (2 g) gave FAR better results than the lower (1 g). And the three proteins were not very different from one-another, with a possible trend towards the whey protein. What is not shown here (for reasons of simplicity) is that another graphic table in the JMP results shows which factors had interactions with other factors (positive or negative interactions). And this is one of the most exciting parts of using design of experiments with multi-factor components. It is, in my estimation, the interactions that really help explain how our rearing systems work.

By using a DOE approach we can better explore what factors are of significance in our rearing systems, the direction of their influence (positive or negative), and the factors which interact in ways that would not be intuitively predictable. Therefore, my teaching approach is to examine our rearing systems through the DOE approach! More about this will be presented in subsequent blogs and web pages.

More about contents of insect rearing online courses

As discussed in the recent example regarding O2 and CO2 in rearing containers, a deficit of O2 or an excess of CO2 are forms of stress often faced by insects in rearing situations. A key point made in Professor Cohen’s classes is that stress factors can lead to reduction of quality or fitness of our target insects. A major topic in my lectures is oxidative stress and how insects deal with this universal factor. But in the context of the O2 and CO2 levels in the rearing containers, our reared insects can be “fitness-challenged” by diet factors as well as such environmental factors such as temperature and density of the insect populations.

In a reliable and meaningful quality control system, we try to find how well our insects are doing with their rearing conditions (their fitness), and a really sensitive and objective way of determining fitness responses to rearing factors is through analysis of the O2 utilisation and CO2 output. One of our current research inquiries is application of a respirometry system (the Q-Box Respiration Analyzer) to measure the O2 consumption and CO2 output under various rearing conditions. In our current inquiry into O2/CO2 metabolism, we are placing insects in the respirometer chamber and measuring their gas exchange under various conditions such as temperature variations, population density, and diet modifications (where proteins, lipids, and carbohydrates are provided in different proportions). This measurement of metabolism is a direct way of evaluating the degree of stress in our target insects. The setup can be seen in the image below:

Q-Box Respiration Measurement System

While the relationships between diet profiles, temperature, population density, etc. are complex, it becomes clear that determination of how the various rearing factors affect rearing outputs and fitness/quality. For some students in these courses, this model of inquiry is a guide to improving their own rearing systems. For other (most) students, the value of this discussion is to expand their awareness of the intricate and interactive factors that prevail in their rearing systems. The lesson that some seemingly simple factor such as changing the relative amount or type of carbohydrate in a diet (or lipid or protein) can drastically change the insects’ fitness and ability to fly or to store nutrient reserves.

The KNOW YOUR INSECT lesson becomes part of the students’ thinking habits as they go about approaching their rearing systems.

Gas Exchange in Rearing Systems

This important topic is too often neglected in dealing with quality, fitness, and stress in insect rearing systems. I discuss this in depth in my rearing courses, and I provide here a sample of what I discuss.

First, it is important to realize that for nearly all metabolic functions, insects utilise oxygen and release carbon dioxide as a waste. the normal atmospheric O2 level is slightly under 21%, and the CO2 content is about 0.04% (often stated as 400 parts per million). In nature, insects generally have access to the normal levels of O2 and CO2, which raises the question of what levels of these gases are present in our rearing containers? Another important question is what are the consequences of abnormal levels of these gases? To begin to answer the first question, I used an O2 and CO2 measuring apparatus (see picture below) to determine the levels of these gases in a container where I was rearing painted lady butterfly larvae (Vanessa cardui).

Figure 1. Measuring O2/CO2 in Painted Lady Containers

Figure 2. Measuring gas exchange in Painted Lady Rearing Units

Figures 1 and 2 show measurements of rearing containers for painted lady larvae. In the containers in Figure 1, we found the O2 content to be 19.4% and the CO2 content to be 0.4% (roughly 10 times normal atmospheric CO2). These readings indicate that even in non-crowded rearing conditions seen here, there is an indication that the insects may be chronically in an oxygen-depleted atmosphere (a hypoxic situation) and also in a chronically elevated CO2 atmosphere. This raises the question about what the possible effects are from this chronic “gas exchange stress.”

One hint as to the effects of this stress is to be derived from a recent paper by VandenBrooks et al. 2018, where the authors show that in Drosophila melanogaster, there are significant changes in the characteristics of the gas exchange system of D. melanogaster, the tracheoles, and the respiratory organelles, the mitochondria.

Figure 3. Tracheole diameter (in microns) at 3 levels of O2 in rearing atmosphere (12, 21, and 31%) redrawn from VanderBrooks et al. 2018. The authors showed that there were significant changes in the diameter, branching, and numbers of tracheoles as well as significant changes to the biomass of mitochondria as a function of chronic hyperoxia and hypooxia conditions.

The implications of these findings are of potential great consequence in shaping the fitness of insects from our rearing systems where the conditions are often crowded and of untested atmospheres inside rearing containers.

This type of discussion is typical of what Professor Cohen covers in the current set of rearing courses. The potential for stress from all these parameters is ever-present: thermal, gas exchange, humidity, lighting, diet, microbes, and countless other conditions.

New Courses Starting in October, 2021

Allen Carson Cohen will be offering the three live online courses in Insect Rearing Systems, starting in October (5) and ending in December (30), 2021. The live, synchronous courses include extensive treatment (lectures, videos, tutorials, and discussions) of the basics of insect rearing. Professor Cohen’s emphasis in the three courses is on treating rearing systems in a scientific way, applying design of experiments extensively. Students with little or no background in statistics will learn how the most up-to-date procedures in insect rearing can be developed and improved through using designs such as response surface, full-factorial, and mixture designs. The courses are based on Professor Cohen’s recent books Insect Diets: Science and Technology (2015) and Design, Operation, and Control of Insect Rearing Systems (2021), both from CRC Press.

The courses treat all aspects of rearing, starting with basic understanding of the biology of the insects that we rear and the basic biological, physical and chemical characteristics of diets, environments, microbial interactions, genetics, and facilities. Once the basics are established Professor Cohen guides students through the implications of the various fundamentals and concepts to fitness and quality of reared insects. Professor Cohen draws from literature that covers the oldest works on insect rearing through publications that are recently published.

In these courses, Professor Cohen takes the approach of understanding the insects through the concepts of homeostasis and stress factors that stem from all levels of rearing system organization. Furthermore, Cohen constantly applies the rearing background to the specific issues of interest to students. Registration costs are $250 per course, or $750 for all three courses (which may be taken out of sequence). The courses each last for 4 weeks (8 lectures), for a total of 12 weeks of learning experiences for the whole sequence. Courses are taught through Zoom and Moodle, and students are provided with course materials (lecture notes, and many PDFs of relevant and current materials). The three courses constitute more than 52 hours of instruction plus the option of post-class discussions of topics of special interest to students. Please see future blog pages for further discussion of the unique nature of these courses.

Just Finished Live, Online Courses in Insect Rearing

We just finished our first year of teaching live, online courses in rearing! The courses consisted of 3-courses, each course lasting for one month, with Course 1 on insect diets, Course 2 on rearing operating systems, and Course 3 focusing on design and control of rearing systems. About 40 students/participants were in the courses, which consisted of eight 2.5 hour lectures, with discussion and plenty of examples of rearing fundamentals. One of the key features of these courses was the LIVE tutorials on applying JMP’s Design of Experiments and statistical process/quality control.

One of the major themes of these courses is the quest to understand the totality of rearing systems in terms of interacting components. Professor Cohen emphasizes that your rearing system is an artificial ecological niche, and just as organisms’ ecology must be understood from the perspective of their NATURAL niches, in rearing systems, we are best served by understanding the artificial niche conditions that we impose on our rearing subjects

The Diet Matrix (from Cohen 2004 and 2015), showing a few of the interactions between diet components and the target insect.

The figure here shows an artificial diet containing soy flour, wheat germ, agar, and other typical diet components. The theme of this picture is the complexity of diet components such as the electropherogram (lower right) showing the effects of cooking soy proteins (lanes 6, 7, and 8) vs. presenting raw soy proteins (lanes 3, 4, and 5). The cooked proteins are denatured, a process which limits the anti-nutritional qualities of soy (removing inhibition of proteases and other “killing’ other enzymes that are potentially damaging to the insects. The lipids (in red) interact with the proteins in a way that makes the lipoprotein complexes more available to the insects’ digestive system. The various proteins interact with the agar (or other gelling agents) to make the texture of the diet more palatable to the insect, and the interactions may help stabilize the various diet components so that the oxidation of lipids and other damaging reactions such as destruction of ascorbic acid is averted or reduced in rate of deterioration. All these (AND MANY MORE) interactions are part of the concept of diet matrix characteristics.

These are a few of the typical topics that we take up in the live, synchronous rearing courses. It’s certainly complex, but it’s what we need to understand to make our rearing systems work the way we want them to work!

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