Yes, superworms (Zophobas morio) readily eat each other, and cannibalism is one of the most well-documented behaviors in this species. It happens most often when larvae are overcrowded, underfed, or when vulnerable individuals like pupae are left exposed to active larvae. In one study, when 50 pupae were placed with a natural population of active larvae, only 4 out of 50 (8%) survived after five days.
Why Superworms Turn Cannibalistic
Cannibalism in superworms is driven by a combination of overlapping stressors, not a single trigger. The two biggest factors are food deprivation and overcrowding, and they tend to compound each other. In insect research, starvation is recognized as one of the strongest triggers for aggression and cannibalism, with aggressive behavior and killing beginning within 24 hours of food removal in dense colonies. When food is unlimited, colonies show almost no aggression.
Overcrowding alone can be enough. One research group studying superworm digestion found that their initial trials with grouped, starving superworms produced so much cannibalism they had to redesign the experiment and house the starving control animals individually. When they later compared results to a similar study that used ten times higher larval densities, that denser experiment saw survival drop to roughly 70% after three weeks, while the lower-density design kept far more animals alive. The takeaway: reducing density meaningfully reduces killing, even when other conditions are identical.
Nutritional quality matters too, not just quantity. Research on closely related darkling beetles found that strains with higher cannibalism rates were compensating for poor nutritional adaptation. Beetles that couldn’t extract enough nutrition from their standard diet survived better when they had access to eggs from their own species. In other words, cannibalism isn’t random violence. It’s a calorie strategy, and larvae in nutritionally poor conditions are more likely to treat each other as food.
Pupae Are the Most Vulnerable Targets
Superworm pupae are soft, immobile, and defenseless, which makes them easy targets. The 92% mortality rate seen when pupae were left with active larvae reflects just how dangerous this life stage is in a colony setting. This vulnerability is so significant that it appears to have shaped the species’ biology over evolutionary time. Superworm larvae actually suppress their own pupation when they’re crowded together: physical contact between larvae sends a signal that delays the transition to the pupal stage. Researchers have confirmed this isn’t caused by pheromones, sound, or visual cues. It’s purely mechanical, triggered by the physical bumping and touching between larvae.
This built-in delay is essentially a survival mechanism. A larva that pupated in a crowded colony would almost certainly be eaten. So instead, larvae in groups continue molting through additional larval stages (up to 18 instars) without ever pupating, sometimes until they die of old age. Only when a larva is isolated does it reliably pupate, typically after 16 or 17 molts. This is why breeders who want to produce beetles must separate individual larvae into their own containers.
Molting Larvae Are Also at Risk
Pupae aren’t the only vulnerable ones. Any larva in the process of molting is temporarily soft and sluggish, making it a target for nearby larvae. Superworms go through many molts before reaching full size, and each molt creates a brief window where the freshly shed larva has a soft exoskeleton and limited ability to defend itself or escape. In a crowded bin with hungry neighbors, that window can be fatal.
How to Minimize Cannibalism in a Colony
You can’t eliminate the instinct, but you can remove nearly all the triggers. The goal is to make cannibalism unnecessary by keeping the colony well-fed, hydrated, and uncrowded.
- Keep food constantly available. A steady supply of dry grain (oats or wheat bran) as a base food, supplemented with fresh vegetables like carrots or potatoes for moisture, removes the two biggest nutritional triggers: calorie shortage and dehydration. If larvae never go hungry, the drive to cannibalize drops dramatically.
- Avoid overcrowding. Research consistently shows that lower densities produce better survival. Give larvae enough space that they aren’t in constant physical contact. A shallow, wide container is better than a deep, narrow one, since it spreads the population across more surface area.
- Isolate larvae for pupation. Any larva you want to pupate must be separated from the colony. Individual containers (small cups or compartmented trays) prevent the colony from eating the defenseless pupae. Without isolation, pupation either won’t happen or the pupa will be consumed.
- Remove dead or injured individuals promptly. Injury is a known independent trigger for cannibalism in insect colonies. A wounded or dead larva attracts feeding behavior from healthy ones, and once that starts, it can escalate.
- Provide adequate substrate depth. A layer of bran or oats several centimeters deep gives larvae places to burrow and reduces the constant physical contact that both triggers aggression and suppresses pupation.
Is Some Cannibalism Normal?
In any large superworm colony, occasional cannibalism is essentially unavoidable. You’ll find partially eaten larvae from time to time even in well-maintained bins. This is normal colony behavior and not a sign of catastrophic husbandry failure. The distinction is between occasional losses and widespread killing. If you’re finding multiple dead or partially consumed larvae every few days, that points to overcrowding, insufficient food, or inadequate moisture. A healthy, well-stocked colony with reasonable density will still lose a few individuals, but the losses should be infrequent enough that the population grows steadily.
For keepers who raise superworms as feeder insects, the practical math is straightforward: the cost of keeping food and moisture constantly available is far less than the cost of replacing larvae lost to cannibalism. A colony that eats itself is an underfed or overcrowded colony.