The Indian meal moth is one of the world’s most pervasive agricultural pests, since it can survive in a huge variety of conditions and eagerly feeds on grain. It is also one of the most fascinating agricultural pests, with an unusual life cycle and diverse habits.
1- Eggs Can Go Dormant
The moths suffer in extreme weather, especially when they are still in their larval life stage. If the weather is too warm or cold when the eggs hatch, the larvae will simply die. They developed a technique called diapause to deal with that risk, which causes the eggs to go dormant in hot or cold weather. Their life cycle essentially pauses, and starts again when the weather is correct for the insects to thrive.
2- It Eats Almost Any Plant
The moth is a dangerous pest because it can eat many different plants. Grains are the most common targets, including processed grains. It will also eat nuts and fruit when they are available, so very few farms can entirely avoid problems with it.
3- Strategic Cannibalism
The moths normally refuse to eat meat and other animal products, but they will engage in cannibalism from time to time, although they only target larvae instead of eating adults. Unlike most species, which eat their own sick larvae in order to conserve resources to raise the healthy ones, the moths prefer to eat their healthy young instead of the sick ones. That is probably a survival adaptation, since they can get sick from eating their sickly young.
4- Light Preferences
Indian meal moths have a strong preference for blue light, to the point where farmers can use blue lights to attract them to specific areas. This is because they naturally go foraging when the sun is setting, which is a time when most of the available light is blue. They can still function at other times, but they will always be more attracted to sources of blue light than to any other light source.
5- Variable Lifespan
The entire life cycle of these moths can vary from roughly 30 to 300 days, which is far more variable than normal for insects. The average lifespan is approximately 50 days in most areas. Scientists do not fully understand every variable that contributes to their lifespan, but they have noticed that their diet has a large impact on how quickly the moths develop. Temperatures also seem to have an impact, with diapause being responsible for the largest increases in lifespan.
6- Pesticide Resistance
Farmers usually rely on pesticides to deal with these moths, but that tactic may nor work very well in the future. Most treatments rely on a bacteria called Bacillus thuringiensis, which lives in the soil and has the potential to kill them. Unfortunately, the moths are developing a resistance to the bacteria due to natural selection. Some populations are developing similar resistances to a variety of other pesticides. It is likely that farmers will need to come up with new pest control methods in the future, once those resistances become stronger and even more common in the species.
7- Natural Predators
There is some hope that natural predation will be able to keep the population under control. Indian meal moths face a huge number of predators, such as many birds and bats, lizards, cats, dogs, and even bears. None of them live exclusively on the moths, but they are all ager to eat them when they are available. Ensuring that they have the opportunity to feast on the moths before they can destroy crops may turn out to be a good way to deal with the problem if pesticide resistances become too common.
8- Spreading Populations
The moths have spread all over the world. Some of their migration is natural, since the larvae will travel long distances to find food or appropriate pupation sites. On the other hand, they can also spread by laying eggs in sacks of grain or other foods before those sacks get shipped to a new area. Modern farmers usually work to make sure that doesn’t happen, but accidents can still provide the moths with a chance to hitch a ride to a new home.