How long do moths live?
How long moths will live varies by species and when their eggs are laid. The common brown house moth’s life cycle on average takes 11-13 months depending on conditions but they will only spend 2 – 4 months of that as an adult moth.
The answer to how long do moths live can vary quite drastically from species to species. It also depends on whether you are including their entire lifecycle. The common brown house moth’s life cycle on average takes 11-13 months depending on conditions but they will only spend 2 – 4 months of that as a moth. In contrast, the sphinx moth will live for 2 – 3 months, whereas the silkworm moth once emerged will live for around a week. One of the shortest living moths is the yucca moth who will typically only survive for about 2 days after metamorphosis.
According to the Lepidopterists’ Society one of the reasons that some moths have a much shorter lifespan than others, predominantly stems from them actually having no way to ingest food. Some moths emerge from their cocoons without mouths. They live out their entire moth existence on stored nutrients, with their sole mission of reproduction to ensure the next generation of moth.
Before they become moths they are larvae or moth caterpillars. That is when these shorter living moths store up their energy. The length of time that the moth lives in these earlier stages of development will depend on habitat, climate and weather conditions according to the Lepidopterists’ Society.
The Arctic woolly bear caterpillar can live for 14 years, feeding during the summer and freezing in the winter, finally thawing out in spring. Once they pupate and emerge as a moth they have only a few days to mate before they die.
Adult Moth’s Total Life Span
As we touched on previously the total lifespan really should include the time that they spend in the larval and pupal stages, as well as in their final adult moth stage. Ultimately their lifespan is based around the number of flights that they will have. A flight is a new generation of adults. So for instance, if a particular species has “two flights from May through September it typically means that one generation will move out of the pupal stage in spring and a second batch will emerge in the summer. The time of the moth’s emergence will typically depend on latitude. The total lifespan of these two separate generations will vary quite differently depending on their chosen strategy for the winter.
So if the spring flight resulted from the eggs that had been laid in the fall by last summer’s flight, then the total lifespan for the spring flight would be 10-11 months. Whereas eggs laid in May by those adults will develop much quicker because of the higher temperatures. This new flight will emerge after about 2-3 months which means their total life span will only be 3-4 months. The exception to this rule is when adult moths over winter, this means the spring flight will emerge from eggs laid in spring and as such the summer flight will be the longest living moths.
Not all species of moth will have two flights a year. Some will have only one flight, or a total life span of around a year. There are even some arctic butterflies that supposedly have a two-year cycle as a result of the growing conditions and the scarcity of food whilst in the larval stage. There are even dessert species that have a life cycle of a year but can hibernate up to 7 years in the larval or pupal stage just waiting for enough rainfall to grow the host plant.
Life Cycle Of The Moth
We’re sure that at this point you know that moths do not start out as moths. Their lifecycle involves various stages that they must go through. From egg to larva (also known as a moth caterpillar), next into the pupa stage, and lastly emerging as an adult moth. Each of the stages is highly critical for the growth and development of what will become a fully grown adult moth. Each stage differs from the next, so let’s take a look at these stages now.
Stage 1: Embryonic Stage – The Egg
This embryonic stage is the first stage of the moth’s life cycle. This is the stage when the embryo will develop inside the egg. This is not too dissimilar to how a bird or fish embryo develops inside their eggs. All of this begins once a male and female moth pair mate. There is a highly complicated and pretty intense mating ritual that they will go through, ending with the fertilising of the eggs inside the female moth.
The female moth will then find a suitable spot to lay her eggs. The best spots tend to have a large amount of plant matter. The plants will provide a quality food source for the larvae or moth caterpillars upon hatching,
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On a side note this is why you will find moths in wardrobes or closets with your clothes. Their moth larvae or caterpillars are known to enjoy eating particular clothes fibres. You can find out more about moths eating clothes here.
Freshly laid moth eggs can take around 4 to 10 days to gestate. Any eggs that are going to hatch should have hatched within 10 days. It does take certain conditions for the moth eggs to gestate and for the embryos to mature so the time can vary up to that 10 day mark. They do require a fair amount of humidity and warmer temperature but ultimately the length of time that the eggs gestate for will also vary depending on the particular moth species.
Fun Fact: A female moth can lay 40-50 eggs in about 2 weeks. Once her eggs have been laid, the female moth dies shortly after. That being said there are a number of moth species that can lay 200-300 eggs in their lifetime. They embryos then take around 10 days to absorb nutrients, grow and finally emerge as a larva, which is often referred to as a caterpillar.
Stage 2: The Larval Stage
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First just to clarify things here. “larva” is the singular, whilst “larvae” is used for plural. For the remainder of this article let’s just call any moth larvae caterpillars, as it just sounds a bit nicer.
Upon hatching the first thing the caterpillar eats is its shell. This shell is packed with a lot of valuable nutrients such as proteins, vitamins and other good stuff that the caterpillars need to survive and thrive. There is not too much point getting to much into how these caterpillars look, as there are so many different moth species out there and many of the all look quite different.
When the caterpillars initially hatch, they are said to be in their first instar. These instars are essentially the different stages of development for moth caterpillars. They go through different processes, such as milting and shedding, the same way the snakes, spiders and all sorts of animals do. As these guys have an exoskeleton, this skin or shell protecting them does not grow like their bodies. Therefore, they need to shed their old ones, growing new ones that fit the size of their new bodies. If we’re getting technical, which let’s face it, we are; the shell or their skin, whatever it is being shed, is actually called a cuticle. Before its first shed, the caterpillar is in its first instar.
Just like their shells, caterpillars will usually eat their shed cuticles, again they tend to be full of useful proteins and other nutrients that aid their growth. After the first shed, they are now in their second instar. Many caterpillars will often significantly change visually at each new instar, whilst others will look the same just bigger. The number of instars that a caterpillar will ultimately go through depends very much on their diet, climate and the species of moth.
Caterpillars are little eating machines. In preparation for the next stage of its life cycle, caterpillars will consume around 2,700 times its body weight. This next stage, the pupal stage is literally where the magic happens, and these caterpillars will transform into a moth. Like all things, the length of time that a caterpillar will remain in its larval stage for will vary depending on the species, the climate, and also the amount and quality of the food.
Once a caterpillar reaches its final instar it is now ready to pupate. Once ready the caterpillar will become a cocoon and transform at last into a moth. To do this the caterpillar will usually wander off from the plant it has been hosting, looking for a space that is safely away from predators, is warm and humid. Upon finding their pupation site, they will shed their last cuticle in order to begin their transformation.
Stage 3: The Pupal Stage
We have now reached the pupal stage. This is truly the most fascinating stage of the moth life cycle. This is the stage where the caterpillar will undergo its transformation into a fully-grown adult moth with wings and everything.
Now the particularly interesting part here is that the moth when it’s in the pupal stage is referred to as being in a cocoon. Whereas for butterflies, when they are in their pupal stage, they are in a chrysalis. This is the last stage before taking flight when the caterpillar or larva transforms into an adult moth.
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Caterpillars have the amazing ability to spin a kind of silk-like material that’s made from proteins it produces. They will spin this silk into a sort of protective sack or shell, this is what is referred to as a cocoon. Inside this cocoon is where all the transformation will occur. The cocoon offers the vulnerable caterpillar some protection from some insects and smaller creatures, but also and probably more importantly keeps everything together during the transformation process. We could imagine things getting a little messy otherwise.
We would forgive you for thinking that this is a resting stage. Whilst it doesn’t actually eat anything or really move at all during this stage, it is most certainly not resting. Every bit of stored energy from its time munching its way through just about everything as a caterpillar, is now being put to use. All of that food energy is now being burnt up for the most energy-intensive process that the moth will ever have to go through. This transformation is more accurately referred to as metamorphosis.
During the metamorphosis, the caterpillar doesn’t actually grow into a moth at all. Rather it goes through a process called histolysis. This is terrifying but we can appreciate the requirement of it if a caterpillar is ever going to fly. There are special transformative cells that stay dormant and are inactive during the pupal stage of the moth’s life cycle. Essentially these cells break the caterpillar down into a pile of cells, literally a sack of questionably conscious goo. Then rebuilding itself back into a moth.
This rebuilding process is known as histogenesis and is both fascinating and creepy A.F. If you have a thing for etymology, the word comes from the Latin words, “Histo” which mean “tissue” and then the word “Genesis” which mean “the beginning”. We can see how this quite effectively describes what is happening during the pupal stage. We’re not going to go too much into the science of it all here as it’s probably a bit unnecessarily complex, but basically, these special cells rearrange the DNA and all the other cells inside the cocoon. This is what creates the adult moth.
Fun fact: It’s interesting to think whether or not the adult moths that emerge have any existing recollection of the other stages it went through. Well, there was a study done in Georgetown, where researchers test this on a range of different aged caterpillars by teaching them to avoid a certain odour. The results showed that caterpillars who were taught to avoid the odour in their last larval stage were able to recall this information as adult moths.
This process usually takes between 5 and 21 days from cocoon to adult moth. However, the process really is impacted by the environment. There are different signals which the pupa/moth will pick up on, and this will let it know that it is the right time to emerge from its cocoon. These are either environmental signals as to the appropriate time of year or else they are chemical based, coming from inside the moth itself, letting it know that its metamorphosis process is complete.
Stage 4: The Imaginal Stage – The Adult Moth
This is the last stage of the moth life cycle. The adult moth has emerged, with a new set of wings and can actually fly around. Technically and adult moth is named an “imago”, and this is why we refer to this as the imaginal stage.
Getting out of the cocoon is no easy feat, they don’t just slip out, it takes them a bit of time. They are soft, fragile and quite weak. Once they have finally emerged fully from their cocoon, they are very bloated and have shriveled wings. It will be a few hours before it is able to take its first flight as an adult moth.
See during the pupal stage when the metamorphosis is taking place, quite a bit of waste is produced. This waste is called meconium and is a slimy orangey red liquid which the moths will defecate out once ready in order to fly. It’s pretty disgusting!
In addition to this, the moths need to get their hemolymph pumping. That’s essentially the equivalent to invertebrate blood. It takes a couple of hours to fully inflate the wings to their full size allowing them to actually fly. Not just that but their wings are also wet from being inside that soupy cocoon. The moths have to allow them to dry. Until they’re dry it will not fly! This is a highly dangerous time for the moth as they are now completely unprotected and very vulnerable.
Adult moths don’t tend to live too long generally but as we’ve already discussed, it depends on the species of the moth as well as its latitude. Some moths live for a week, others for months. Some moths can live up to 10 months.
At the end of the day, most moths out there are not likely to reach old age. The majority will be killed by predators or environmental factors well before they reach the end of their life cycle. Every moths aim is to reproduce. The female moths tend to die after laying their eggs, completing the life cycle of the moth and beginning an entirely new cycle. Male moths will not live much longer after mating either.
So in conclusion, how long do moths live? Well whilst the life expectancy of a moth will vary widely depending on the species, environmental factors and even the latitude. It’s safe to say that their life cycle is fascinating and there is a lot more involved than most people may realise.