Imperial hairstreak facts for kids
Quick facts for kids Imperial hairstreak |
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Jalmenus
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J. evagoras
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| Jalmenus evagoras (Donovan, 1805)
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The Jalmenus evagoras, also known as the imperial hairstreak, imperial blue, or common imperial blue, is a small, shiny blue butterfly. It belongs to the Lycaenidae family. You can often find this butterfly in the eastern coastal areas of Australia.
This butterfly is special because it has a unique partnership, called mutualism, with ants from the Iridomyrmex group. The ants protect the young butterflies (larvae and pupae). In return, the butterfly larvae give the ants a sugary food. This partnership helps the butterflies survive and have more babies. J. evagoras butterflies live and eat on Acacia plants. So, you'll only find them where their favorite plants and ants live together.
Contents
Description
The wings of the Jalmenus evagoras butterfly are a shiny metallic blue with black edges. Their back wings have small tails and orange spots near the bottom. The underside of their wings is a light brown color with black stripes and orange spots, similar to the top side. This butterfly can have a wingspan of up to 4 centimeters.
It's hard to tell male and female adult butterflies apart just by looking at them. However, when they are in the pupa stage (like a cocoon), female pupae can be up to 60% larger than males.
Where They Live
The Jalmenus evagoras butterfly lives along the east coast of Australia. This includes Queensland, New South Wales, Victoria, and the Australian Capital Territory. You won't find them everywhere in this area; their groups are spread out. This is partly because they need special Acacia plants that are rich in nitrogen, and specific kinds of Iridomyrmex ants.
Even though their food plants are common, not all of them have the right nutrients for the butterflies to support their ant friends. Also, not all areas have the right ant colonies. These butterflies live in small breeding groups, sometimes around just one tree. They tend to stay in the same place almost every day of their adult lives. J. evagoras has many breeding cycles in a year. They usually have two cycles in the southern parts of their range and three or four in the northern parts.
Food Resources
Larvae
Young Jalmenus evagoras (larvae) eat more than twenty-five different types of Acacia plants. They have special glands that make a sugary liquid for the ants. This liquid is a reward for the ants protecting them from other bugs that want to eat them or lay eggs inside them. This liquid is made of sugars and amino acids.
Because they depend on ants, the butterflies choose plants that help them make enough of this food. For example, they often pick plants that are good at collecting nitrogen or are rich in protein. Eating these protein-rich plants helps the larvae produce enough amino acids to keep their ant friends happy.
Adults
Adult female J. evagoras butterflies can lay more eggs and live longer if they drink nectar from flowers that have a lot of sugar. More sugar can make a female butterfly live from four days up to twenty-eight days. It can also help her lay up to three times more eggs! Both sugar and amino acids make females eat more often. However, only sugar affects how many eggs they lay or how long they live.
Parental Care
Laying Eggs (Oviposition)
Female J. evagoras butterflies usually lay their eggs in holes in the bark of Acacia trees. The tree trunk is the most common spot, but some also lay eggs on leaves. Scientists have seen female butterflies change where they lay eggs during the season, moving from the outside of plants to inside cracks in the trunk.
Their choice of where to lay eggs depends on several things. This includes the type of plant, how healthy it is, and if ants or other J. evagoras larvae are nearby.
Choosing a Host Plant
A big reason for choosing a plant is whether friendly ants are there. Female butterflies are more likely to lay eggs on plants that have ants. They can even tell the difference between different ant species and pick the ones that are best at protecting their young. If other larvae are present, it can also influence where eggs are laid. This is because more larvae usually attract more ants to the plant.
Females can also sense how good the plant is for their babies. They check things like the amount of nitrogen and water in the leaves. They might use clues like the color of the leaf (darker green often means more nutrients) and even taste the plant once they land on it. The female butterfly uses all these clues before and after landing to make sure her eggs have the best chance to survive.
In Queensland, females often chose younger Acacia trees to lay eggs. In other places, young butterflies were found more often on older trees. Larvae, no matter the tree size, prefer to eat the new growth at the ends of branches.
Social Behavior
Young Butterflies Staying Together
Young J. evagoras butterflies (larvae and pupae) like to stay in groups. Eggs are laid in clusters, and then the larvae and pupae stay close together even after hatching. Young larvae especially tend to group up more when their ant friends are around. Older larvae are usually not as influenced by the ants. However, if there are not many ants on the host plant, older larvae might decide to turn into pupae near other individuals. Larvae can follow ant trails to find other young butterflies of their own kind. Other clues like making sounds (stridulation) and silk trails might also help them stay together.
Life Cycle
In Nature
Adult J. evagoras butterflies fly around from late October or November until April. Near Sydney, you can most often see young butterflies in October and early February. The eggs spend the winter dormant. So, eggs laid near the end of the season will wait until spring to hatch. If eggs are laid in the spring, they hatch quickly and the new butterflies reproduce within the next two months.
In the Lab
In a lab, it takes about four weeks for larvae to grow at 28°C. If ants are present, the larvae can grow faster, by up to five days. Once the larvae turn into pupae, ants still tend to them. However, it hasn't been shown that ants make the pupa stage shorter. The pupa stage lasts about seven days.
Enemies
Predators
The main enemies that eat J. evagoras larvae are other arthropods. These include wasps, ponerine ants, assassin bugs, and spiders. When ant guards are present with the larvae, attacks from these insects drop a lot. Adult butterflies are sometimes eaten by birds. However, young butterflies are not affected by these larger predators.
Parasites
J. evagoras butterflies are often attacked by different kinds of wasps at various stages of their life. The trichogrammatid wasp lays its eggs inside the butterfly's eggs. The braconid wasp is a major parasite of the larvae. This wasp attacks young larvae and kills them when it emerges from the fourth stage larva. Chalcid wasps attack the pupae, laying eggs inside them. The young chalcid wasps then emerge from the butterfly pupae.
Having attendant ants has been shown to protect against the braconid wasp and the trichogrammatid wasp in some places. However, ants do not seem to protect against chalcid wasps.
Reproduction
How Males Find Mates
Adult male butterflies look for mates by checking out groups of larvae on Acacia plants. Male Jalmenus evagoras butterflies usually emerge before the females. To find mates, they regularly fly around trees that have pupae. They know that healthy larvae and pupae are found where ants are present. Because healthy young butterflies live with ants, males who learn this trick can find suitable females before they are fully grown. This saves the males time and energy. Males hover around the young butterflies, often using their antennae to "taste" and figure out the age and sex of the larvae.
Males are not very picky when looking for mates. They sometimes try to mate with other males that are just emerging. Female pupae are generally a bit larger than male pupae. So, size could be a way to tell the difference and avoid mistakes. However, male Jalmenus evagoras don't seem to rely on size. There's no proof they land on bigger pupae, only on pupae that have more ants tending to them. This shows how important the presence of ants is for mate selection.
Female and Male Interactions
When a female pupa is about to emerge as an adult, up to thirty males will rush to the spot. This creates a "mating ball." This competitive gathering of males around the pupa is called the "explosive mating strategy." After a female emerges, mating happens right away, usually before her wings have a chance to harden and expand.
Males are not territorial and will easily leave one plant to join another mating ball. Also, males mate many times. If they are successful, they have been seen mating as many as seven times in their lives. A male's success in mating depends on how long he lives, how often he finds females, and how good he is at mating.
Female Jalmenus evagoras butterflies usually mate with only one male in their lifetime. In experiments, females seem to stay at a certain spot for shorter times than males. It's not known if this is because females have a shorter lifespan or if they just move away more. The idea that females have a shorter lifespan makes sense, since they only mate once and don't need to live longer to find multiple mates.
Special Partnership (Mutualism)
With Ants
Jalmenus evagoras butterflies have a special partnership, or mutualism, with worker ants from the Iridomyrmex group. They most often team up with Iridomyrmex anceps and Iridomyrmex rufoniger, but they can also work with other ant species. The ants protect the young J. evagoras (larvae and pupae) from predators and parasites. In return, the ants get food secretions from the butterfly larvae or pupae.
Groups of larvae that have ants protecting them have a much better chance of surviving than those without ants. This partnership with ants is also very important for how J. evagoras butterflies find mates. Female butterflies use the presence of ants to decide where to lay their eggs. Males use ants to find healthy pupae that are about to emerge for mating.
Butterfly Adaptations for Ants
Larvae and pupae of J. evagoras have special body parts that help them with their partnership with ants. Larvae have a thick outer skin (called a cuticle) to protect their insides from ant bites. Both pupae and larvae have two kinds of special organs on their bodies that make food for the ants. These are called perforated cupola organs (PCOs) and dorsal nectary organs (DNOs). Both of these contain glands that produce the sugary substances the ants eat.
Besides these food-making organs, the young butterflies also have organs that make sounds. These are called stridulatory organs. Stridulation (making sounds) by older larvae and pupae helps ants find them more easily.
Gallery
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Egg
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Eggs
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Larva
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Pre-pupa
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Pupae tended by ants
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Dorsal view
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Female
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Male
