One of the first things you learn about mealworm farming is they prefer the dark or dimly lit environments. If you buy a mealworm container for instance, the instructions might say place in a dark location. But why is this so? Does it really make a difference if you expose them to light?
Mealworms prefer the dark because it is their natural habitat. In the wild, mealworms burrow in decaying matter or hide under leaves, so mealworms in farms should be raised in a similar manner. They tend to shy away from light.
How Mealworms Benefit from Darkness
Mealworms (Tenebrio molitor) are highly adaptable and can survive in different environments. But ask anyone who is into mealworm farming and they will tell you that darkness or dimly lit locations is ideal for them. There are good reasons for this.
In their natural habitat, mealworms can be found in decaying organic matter like rotting leaves, dead plant material, or animal waste. Mealworms prefer these dark environments because it offers them protection from predators and harsh elements. Over time, mealworms evolved to feel secure in low light or completely dark places. If you want to know more, here is a guide on where to find mealworms.
Mealworms are photophobic, which means they are very sensitive to light. Exposing them to bright light can cause stress and discomfort. In the wild, light attracts potential predators so mealworms shun it. Even in controlled environments, they will try to avoid bright lights.
A dark environment can also help mealworms retain moisture, which is crucial for their survival. Light and sunlight can accelerate moisture evaporation from their bodies. By staying in the dark, mealworms can reduce water loss and maintain their hydration levels.
Effect on Breeding
Mealworms use pheromones to communicate for mating purposes. These pheromones work more effectively in darkness as they are less likely to get dispersed or diluted. For breeding purposes, it only makes sense to keep your mealworms in the dark. This alone can make a difference in terms of how productive your farm can be.
Mealworms go through a process called metamorphosis, where they transform from larvae to pupae and eventually into adult beetles. During the larval stage, mealworms require a safe and stable environment. The dark provides them with a sense of security as it is less likely to attract predators.
Energy Conservation: Being ectothermic, mealworms rely on external sources of heat to regulate their body temperature. A dim environment helps them conserve energy by minimizing heat loss. Without the need to deal with excessive heat or cold, mealworms can focus their energy on growth and other physiological processes.
While mealworms prefer darkness, they are not completely nocturnal. They are opportunistic feeders and will come out if food is available, regardless of the lighting conditions. I left food in a well-lit environment as an experiment and the mealworms went for it.
How Light Affects Mealworms
Light affects mealworms in different ways. True, they tend to avoid it, but they still need some lighting for development. If you don’t want to keep your mealworms in a completely dark bin, dim lighting will do. Now let’s take a look at the many ways light affects them.
Phototaxis
Mealworms exhibit phototaxis, which refers to the movement or orientation of an organism in response to light. Mealworms are negatively phototactic, meaning they tend to move away from light sources. You can see this behavior when mealworms hide in dark crevices during the daytime to avoid light exposure.
Circadian Rhythm
Like other organisms, mealworms have a circadian rhythm. This internal biological clock regulates their sleep patterns, feeding and other physiological processes. Light serves as a cue that affects their circadian rhythm. Exposure to light awakens and alerts mealworms. Darkness on the other hand, means rest and sleep for them.
Molting and Growth
Light also influences mealworm molting and growth. During the larval stage, mealworms molt numerous times, shedding their exoskeleton and growing new ones. Studies have shown that light intensity and duration can affect the timing and frequency of molting. Insufficient light can delay molting and slow their growth. While mealworms may shun light, it’s actually essential.
Related. Mealworm Molting Guide
Light also affects their reproductive behavior. Female darkling beetles require specific light conditions to lay their eggs. They usually prefer dim or dark areas to lay their eggs. if there’s too much light, the beetles will look for other places for their eggs.
Mealworms also prefer dark locations when they enter the pupal stage. This is understandable as mealworms are vulnerable during this period. After they find a suitable location, the mealworms will go into the pupal stage until they turn into beetles.
Behavioral Effects
Mealworms behave in different ways depending on the lighting. Some are more alert when exposed to light and tend to stay awake, looking for potential predators. But if there are no threats, mealworms may rest and sleep.
Some mealworms are also more active during the night or in dark places. For instance, a lot of mealworms sleep during the day. But if you put them in a dark place during daytime, they might become more active. Their bheaior is not only affected by light but also the environment.
Why Mealworms Prefer Dark Over Light
We have seen that light actually provides some benefits for mealworms. It isn’t a stretch to say they need it to survive, albeit in limited amounts. But why do they generally avoid it? There are many reasons why mealworms prefer the dark over light.
Protection
Mealworms in the wild are typically found in dark and decomposing environments. I am talking of locations like soil, leaf litter or decaying wood. These places provide them with protection and insulation from bright light, predators and extreme temperatures. Even if you keep mealworms safe, they will still prefer dark locations.
Natural Light Sensitivity
Like many insects, mealworms have compound eyes that are specialized for low light conditions. They cannot see well in the daytime and better adapted to conditions when light intensity is low.
Exposure to intense light can overwhelm their visual system and potentially damage their eyes. By instinct, mealworms know that the dark is safer for them.
Nocturnal
Mealworms are nocturnal creatures and are most active during the night. Their biology and internal clock are attuned to function optimally in darkness.
Being exposed to constant brightness can disrupt their natural rhythms and behavior. This is how mealworms evolved so it’s not surprising they always burrow into their bedding.
Need for Moisture
Mealworms need moisture in their bodies, and a dark, lightly damp environment suits them fine. In contrast, light and heat can cause their bodies to dry up and lead to dehydration. This is crucial especially if there is no water or moisture source nearby.
By choosing darker environments, mealworms can better regulate their body temperature and moisture levels. It reduces the risk of desiccation and helps them maintain the conditions necessary for their growth and development.
Related. Do Mealworms Need Water?
Mealworms are highly sensitive to temperature fluctuation. Bright lights often lead to higher temperature, and this affects their metabolism. Mealworms can overheat if it gets too hot and through evolution, they can sense that light and heat correlate. A dark environment provides a relatively stable and cooler temperature range for mealworms.
Understanding these behaviors and preferences can help you set up an ideal farm to raise mealworms. This type of information is useful not just for mealworm farmers but also those in the animal husbandry sector.
Conclusion
To summarize: mealworms prefer darkness because it is their natural habitat. They are also sensitive to light. Darkness also helps them maintain moisture. A dark place is also less likely to catch the attention of predators when beetles lay eggs. For these reasons, it is important that you keep your mealworms in dimly lit areas to make them more comfortable and productive.
