Garden Tiger Moth (Arctia caja)
Care Guide
The Garden Tiger is a classic moth species for many breeders and naturalists, familiar in both its colourful adult stage and its fuzzy caterpillars, popularly known as 'woolly bears.' Once a common species found in gardens, fields and wild areas, numbers have declined in recent decades in line with increased pesticide use in agriculture and gardens, among other factors. This guide describes the steps to rearing your own Garden Tigers at home!
Egg & Hatchling Care
Arctia caja eggs should be kept in an airtight plastic container to maintain stable conditions - Temperature and humidity are important factors when hatching eggs.
The eggs are a pale green, their colour and shape remain consistent throughout development until close to hatching when they turn grey/black - this indicates the caterpillar is fully developed inside the egg!
Kept at room temperature, eggs hatch in around two weeks, though they can take up to 3 weeks or longer when kept cooler. Ambient humidity is usually sufficient, best maintained by storing eggs in an airtight plastic container. Open the container once per day to prevent stagnation.
Importantly, do not add host plant leaves before hatching, as leaves release moisture and promote mould growth.
When the eggs begin to hatch, you can add a leaf of host plant as a first meal for the caterpillar. Do not add lots of foliage as this will release too much moisture and water droplets may drown young larvae.
Host Plants for Arctia caja
The Garden Tiger moth is an extremely versatile species, accepting dozens of plant species from different families. We have found some of the best to be:
- Willow (Salix)
- Privet (Ligustrum)
- Dandelion (Taraxacum)
- Dock (Rumex)
Multiple others are reported to be accepted but these are have produced the best results for us in the past.
Also note that you can change the host plant when rearing this species, as they are far less selective than others. A varied diet may even produce larger caterpillars at maturity.
The acceptability of so many host plants means that this species can be reared year-round.
Final Instar Larvae
Mature larvae have a rich orange-brown base colour and black on top with long hairs.
Rearing larvae
The larval (caterpillar) stage is very easy and forgiving in this species, however it is worth noting that develpoment can take significantly longer than other species - around two to four months is typical between hatching and pupation. Note also that development rates can vary significantly even within the same brood, and it is not uncommon for some from each batch to slow down and go into a sort of dormancy if conditions are cool, as this is what they would do in the wild.
Once hatchlings have begun feeding, move them to a new container and leave the remaining eggs to hatch. Line the new container with paper towel to absorb condensation as this will prevent mould buildup leading to disease in the caterpillars, although caja is a very tolerant and forgiving species.
Rear larvae in suitably-sized containers for at least the first and second instars, but they will do well in these conditions up until the fourth stage and even the final instar. It is important to open the plastic containers once or twice a day to refresh the air - do not allow condensation to gather.
Although you can continue rearing the caterpillars in plastic containers throughout their development, they do tend to do better in mesh enclosures for the final (fifth stage). Note that caterpillars, particularly in the later stages, possess hairs which may slightly irritate your skin when handled - this is not dangerous and usually goes away quickly!
Use cut stems in jars to provide food for your larvae once transferred to mesh enclosures. If there are gaps where water is exposed, fill these with tissue to prevent larvae falling in and drowning. Larvae may drink water droplets if misted occasionally, which is useful if foliage is dry, particularly in the heat of summer.
The caterpillar may begin to spin a cocoon among the host plant stems and leaves, or it may wander for a while before selecting a location on the enclosure base (usually the corners) for pupation. In nature they would often pupate among leaf litter or undergrowth. The cocoon is soft and loose, with the caterpillar then pupating inside.
Caterpillars
The long hairs seen on mature caterpillars are used to construct the cocoon!
Caring for Pupae
Once the caterpillar has constructed its cocoon, do not attempt to move them before the caterpillar has pupated inside.
You can typically leave the cocoons to emerge in the rearing cage as they do not require any special conditions. Alternatively you can remove the pupae to emerge in a polystyrene box.
If you struggle to maintain temperature and humidity at suitable levels, a polystyrene box is ideal for keeping cocoons for emergence.
Most of the cocoons will have emerged within 2-3 weeks kept at room temperature, though it is normal for some to emerge a bit more randomly.
Caring for Adult Moths
These beautiful moths require minimal care as adults, simply needing enough room to fly. Their adult lifespan is around one to two weeks and the moths do not feed. They will breed easily, and each female lays hundreds of tiny green eggs - you can release this species at any stage, however releasing adults to breed and lay their eggs in the wild is probably most impactful.
