Metisa plana facts for kids
Quick facts for kids Metisa plana |
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| eggs, larva, pupa and adult of Metisa plana | |
| Scientific classification | |
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Psychidae
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| Genus: |
Metisa
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M. plana
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| Metisa plana Walker, 1883
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The Metisa plana moth is often called a "bagworm" because of the special case its young (larvae) build. It belongs to the Psychidae family, which are all bagworm moths. A scientist named Francis Walker first described this moth in 1883. You can find Metisa plana in places like Sumatra, Malaysia, and Sri Lanka. It's a big problem for oil palm trees, especially the African oil palm.
Contents
The Bagworm Moth's Life Cycle
The Metisa plana moth usually lives for about 90 days from egg to adult. The female moth lays many yellowish eggs, usually between 200 and 300. From one group of eggs, about 140 to 210 tiny baby bagworms (called neonates) can hatch.
Larva Stage and Case Building
When a bagworm larva hatches, it's very small, about 1 millimeter long. About an hour after hatching, the larva starts to build a small case. It uses pieces of oil palm leaves to make this case. The case is shaped like a cone and the larva carries it everywhere.
As the larva grows, it sheds its skin several times. Each time it grows bigger, its case also gets larger. When the larva is in its fourth growth stage (called an instar), its case is covered with loose, round or rectangular leaf pieces. By the sixth instar, the case becomes smooth, without any loose leaf bits. The larva itself turns a whitish-gray color. It takes about 71.5 days for the larva to reach this sixth stage.
When they are very young, the larvae are brownish. They have dark spots on their head and the part of their body behind the head (thorax). Their bodies are covered in tiny sensory hairs. They have well-developed eyes on the sides of their head. The thorax has three pairs of legs with hooks. The abdomen, which is the main part of their body, has five pairs of soft, leg-like parts called prolegs.
Pupa Stage
After the larva is fully grown, it turns into a pupa. This is a resting stage where the moth changes into an adult. A fully grown pupa is about 6.1 millimeters long. Male and female pupae look different. Male pupae have a large blackish head, while female pupae have a creamy yellowish head. Female pupae often move away from the oil palm tree before they change into adults.
Adult Stage and Reproduction
Adult Metisa plana moths look very different depending on if they are male or female. This is called strong sexual dimorphism.
The adult female moth has no wings or legs. Her head is dark brown, and her body is yellowish-brown. She is about 5.5 millimeters long. The male moth, however, has wings. His wingspan is about 10 to 12 millimeters. His wings are smoky brown, and his body is covered in black hairs. He has a chubby head and feathery antennae that look like combs on both sides.
During mating, the male moth cuts open the bottom end of the female's case. After mating, the female lays a large group of eggs inside her case. She then leaves the case and dies a few hours later. The adult male moth usually lives for about 3 to 4 days.
Bagworm Moths and Oil Palms
Metisa plana is a serious problem for oil palm trees. Large numbers of these larvae have been seen in Malaysian oil palm farms since the late 1950s and early 1960s. When there are too many bagworms, they can damage the oil palm leaves, which affects how much oil the trees can produce.
Controlling Bagworm Moths
Farmers use different ways to control these pests.
Chemical Control
Using special chemicals called insecticides is a fast way to get rid of the moths. Farmers spray these chemicals from the ground using a sprayer. Some chemicals like trichlorfon, chlorpyrifos, cypermethrin, and lambda-cyhalothrin can be put into the soil around the trees. Other chemicals like chlorantraniliprole and indoxacarb are also very good at controlling the moths. However, using too many chemicals can sometimes cause problems for the environment.
Natural Control Methods
Nature has its own ways to control pests. Many other insects are natural enemies of the bagworm moth. These include tiny wasps like Brachymeria carinata, Buysmania oxymora, Goryphus bunoh, Eupelmus cotoxanthae, Dolichogenidea metesae, Pediobius anomalus, Pediobius imbreus, and Apanteles metesae. A type of bug called Cosmelestes picticeps also helps.
Farmers can also use a special type of bacteria called Bacillus thuringiensis (often called Bt). This bacteria makes the bagworms sick. Some types of fungi like Paecilomyces fumosoroseus and Metarhizium anisopliae can also infect and kill the moths. Scientists have seen good results with these fungi in labs, and they are studying how well they work on farms.
Humidity and Outbreaks
Scientists have found that when there are many M. plana outbreaks in Malaysian oil palm farms, it is often linked to the amount of moisture in the air, called relative humidity. They can even use information from satellites to guess the humidity levels. By putting this humidity data into computer models, they can predict when and where bagworm outbreaks might happen. This helps farmers prepare and protect their oil palm trees.
