Wattle bagworm

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Wattle bagworm
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Lepidoptera
Family: Psychidae
Genus: Kotochalia
Species:K. junodi
Binomial name
Kotochalia junodi
(Heylaerts, 1890)

Acanthopsyche junodi

The wattle bagworm (Kotochalia junodi, formerly Acanthopsyche junodi) is a species of moth in the family Psychidae. In southern Africa it is a pest of the black wattle ( Acacia mearnsii ) which is grown largely as a source of vegetable tannin. Kotochalia junodi is indigenous to Southern Africa, where it originally fed on indigenous relatives of the wattle.

Moth Group of mostly-nocturnal insects in the order Lepidoptera

Moths comprise a group of insects related to butterflies, belonging to the order Lepidoptera. Most lepidopterans are moths, and there are thought to be approximately 160,000 species of moth, many of which have yet to be described. Most species of moth are nocturnal, but there are also crepuscular and diurnal species.

Africa The second largest and second most-populous continent, mostly in the Northern and Eastern Hemispheres

Africa is the world's second largest and second most-populous continent, being behind Asia in both categories. At about 30.3 million km2 including adjacent islands, it covers 6% of Earth's total surface area and 20% of its land area. With 1.2 billion people as of 2016, it accounts for about 16% of the world's human population. The continent is surrounded by the Mediterranean Sea to the north, the Isthmus of Suez and the Red Sea to the northeast, the Indian Ocean to the southeast and the Atlantic Ocean to the west. The continent includes Madagascar and various archipelagos. It contains 54 fully recognised sovereign states (countries), nine territories and two de facto independent states with limited or no recognition. The majority of the continent and its countries are in the Northern Hemisphere, with a substantial portion and number of countries in the Southern Hemisphere.

<i>Acacia mearnsii</i> species of plant

Acacia mearnsii is a fast-growing, extremely invasive leguminous tree native to Australia. Common names for it include black wattle, Acácia-negra (Portuguese), Australian acacia, Australische Akazie (German), Swartwattel (Afrikaans), Uwatela (Zulu). This plant is now known as one of the worst invasive species in the world.

Like all members of the family Psychidae, the male larva develops into an adult in a mobile silken bag covered with materials such as thorns and twigs. Only once it is mature does it leave the bag to mate. The female never leaves her bag.

Larva juvenile form of distinct animals before metamorphosis

A larva is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle.

Silk fine, lustrous, natural fiber produced by the larvae of various silk moths, especially the species Bombyx mori

Silk is a natural protein fiber, some forms of which can be woven into textiles. The protein fiber of silk is composed mainly of fibroin and is produced by certain insect larvae to form cocoons. The best-known silk is obtained from the cocoons of the larvae of the mulberry silkworm Bombyx mori reared in captivity (sericulture). The shimmering appearance of silk is due to the triangular prism-like structure of the silk fibre, which allows silk cloth to refract incoming light at different angles, thus producing different colors.

In spring the eggs hatch in the bag in which the adult female had grown. Because the female never leaves the tree in which she grew and died, the insects need some other way to move to new trees or in general to disperse, and in fact the newly hatched (first-instar) larva is the dispersive stage of the wattle bagworm life cycle. The larva spins a silken thread on which it may float along on the breeze, much as some species of young spiderlings use gossamer for ballooning in their dispersive phase. Also, birds and probably other agencies may carry some larvae to suitable feeding sites. The young caterpillar does not feed for a day or two after hatching, but eventually, once the dispersive phase is completed, it begins to weave a conical bag of silk, incorporating fragments of plant material such as leaves, twigs and bark. [1]

Biological dispersal movement of individuals from their birth site to their breeding site, as well as the movement from one breeding site to another

Biological dispersal refers to both the movement of individuals from their birth site to their breeding site, as well as the movement from one breeding site to another . Dispersal is also used to describe the movement of propagules such as seeds and spores. Technically, dispersal is defined as any movement that has the potential to lead to gene flow. The act of dispersal involves three phases: departure, transfer, settlement and there are different fitness costs and benefits associated with each of these phases. Through simply moving from one habitat patch to another, the dispersal of an individual has consequences not only for individual fitness, but also for population dynamics, population genetics, and species distribution. Understanding dispersal and the consequences both for evolutionary strategies at a species level, and for processes at an ecosystem level, requires understanding on the type of dispersal, the dispersal range of a given species, and the dispersal mechanisms involved.

Instar A developmental stage of arthropods between moults

An instar is a developmental stage of arthropods, such as insects, between each moult (ecdysis), until sexual maturity is reached. Arthropods must shed the exoskeleton in order to grow or assume a new form. Differences between instars can often be seen in altered body proportions, colors, patterns, changes in the number of body segments or head width. After moulting, i.e. shedding their exoskeleton, the juvenile arthropods continue in their life cycle until they either pupate or moult again. The instar period of growth is fixed; however, in some insects, like the salvinia stem-borer moth, the number of instars depends on early larval nutrition. Some arthropods can continue to moult after sexual maturity, but the stages between these subsequent moults are generally not called instars.

Spider silk filament material produced by spiders

Spider silk is a protein fibre spun by spiders. Spiders use their silk to make webs or other structures, which function as sticky nets to catch other animals, or as nests or cocoons to protect their offspring, or to wrap up prey. They can also use their silk to suspend themselves, to float through the air, or to glide away from predators. Most spiders vary the thickness and stickiness of their silk for different uses.

The thorns and twigs covering the cocoon provide protection against enemies such as mantids. They also serve as camouflage that matches the tree from which the larva had stripped them. As it feeds and grows, it extends the size of the bag until it reaches some 55 mm in length and 18 mm in width and its outline becomes oval. The caterpillar hooks its anal prolegs into the silken lining of the bag. As it feeds and grows, the larva drags the bag wherever it goes until it is full grown and pupates. If alarmed, it shuts the opening by pulling in the slack in front.

Camouflage concealment through color or pattern

Camouflage is the use of any combination of materials, coloration, or illumination for concealment, either by making animals or objects hard to see (crypsis), or by disguising them as something else (mimesis). Examples include the leopard's spotted coat, the battledress of a modern soldier, and the leaf-mimic katydid's wings. A third approach, motion dazzle, confuses the observer with a conspicuous pattern, making the object visible but momentarily harder to locate. The majority of camouflage methods aim for crypsis, often through a general resemblance to the background, high contrast disruptive coloration, eliminating shadow, and countershading. In the open ocean, where there is no background, the principal methods of camouflage are transparency, silvering, and countershading, while the ability to produce light is among other things used for counter-illumination on the undersides of cephalopods such as squid. Some animals, such as chameleons and octopuses, are capable of actively changing their skin pattern and colours, whether for camouflage or for signalling. It is possible that some plants use camouflage to evade being eaten by herbivores.

About February or March the larva is fully grown. It stops feeding, fastens its bag to the tree, and spins an inner lining within which it pupates. The males pupate in April or May and the females perhaps a month later. The winged male emerges from its cocoon some time between August and October. The male does not feed after emerging, and lives for only a few days. It has wings almost clear of scales and flies strongly, seeking out a mature female to inseminate. The female in contrast, remains in her bag after emerging from the pupa. She is a highly specialised, worm-like creature: she has no wings at all, and lacks legs and even eyes; she lies helpless in her shelter, only able to turn her posterior towards the opening of her bag for insemination, and away from the opening for oviposition. The male inserts the point of his abdomen through the neck of the bag and inseminates her. Oviposition starts immediately afterwards, sometimes even before insemination, and in mid- or late winter successful females produces on average about 1600 eggs. They remain in the bag together with the shrunken remains of the mother, hatching about two months later.

Abdomen frontal part of the body between the thorax (chest) and pelvis

The abdomen constitutes the part of the body between the thorax (chest) and pelvis, in humans and in other vertebrates. The abdomen is the frontal part of the abdominal segment of the trunk, the dorsal part of this segment being the back of the abdomen. The region occupied by the abdomen is termed the abdominal cavity. In arthropods it is the posterior tagma of the body; it follows the thorax or cephalothorax. The abdomen stretches from the thorax at the thoracic diaphragm to the pelvis at the pelvic brim. The pelvic brim stretches from the lumbosacral joint to the pubic symphysis and is the edge of the pelvic inlet. The space above this inlet and under the thoracic diaphragm is termed the abdominal cavity. The boundary of the abdominal cavity is the abdominal wall in the front and the peritoneal surface at the rear.

This relatively large clutch size reflects the fact that on average only a few of the larvae survive to reproduce.

Clutch (eggs)

A clutch of eggs is the group of eggs produced by birds, amphibians, or reptiles, often at a single time, particularly those laid in a nest.

The large number of eggs is at least in part an adaptation to the female's inability to fly and the compensatory strategy for dispersion of the newly hatched larvae; wattle bagworm larvae rely on an unusual mode of transport. After hatching as a caterpillar, the insect spins a silk thread and hangs from the end for a few days. The wind or a passing bird sometimes transports the caterpillar to another tree, spreading the species quite effectively, if inefficiently. Given the large number of eggs, there is a reasonable chance that at least some of them will find adventitious transport. The rest either starve, or settle down in the tree where they hatched which is likely to die from defoliation within a few seasons if natural or artificial controls do not prevent it.

The wattle bagworm has many natural enemies. They include parasitic wasps, flies and beetles, and various predators, such as spiders and birds, not to mention fungal diseases such as Entomophthora and Isaria species, bacterial diseases such as Bacillus thuringiensis , and polyhedral virus diseases. Attempts to use such a virus for bagworm control during the 1950s gave results too inconsistent to be satisfactory at the time.

In the wild probably the most important insect enemy of Kotochalia junodi is an interesting parasitoid wasp, a member of the Ichneumonidae, Sericopimpla sericata . In colour the wasp is largely black, yellowish, and red. The female wasp is about 12 mm in length, and like many Ichneumonids she has a protruding ovipositor almost as long as her gaster.

A surprising feature of Sericopimpla sericata habits is that the adult kills bagworms in two ways. In either case it stings them with the ovipositor. The bagworm wriggles and contorts within the bag to avoid attack, but as a rule the female wasp succeeds in stinging it sooner or later. In some cases the female then proceeds to eat the prey herself. The sting paralyses the victim, and the wasp bites a hole in the bag and feeds through it. Such predatory feeding by parasitoids is very unusual. No doubt the female needs the plentiful fat and protein of the victim to produce eggs, much as many blood-sucking female insects need a blood meal before they can lay eggs.

An adequately nourished female will parasitise the bagworm with several stings, perhaps dozens. Paralysed hosts remain fresh for months, long enough for the wasp larvae. [2]

The bagworm routinely infests the large local wattle plantations, which cover more than half a million acres (2,000 km2) in South Africa, primarily in Natal. Natural control of the bagworm is variable, but good enough that the use of the most dangerous insecticides has effectively been discontinued. Nowadays the policy is to spray only heavy infestations, and only at strategic times. In the mid-20th century chlorinated hydrocarbon insecticides such as toxaphene and endrin were the treatments of choice for control of wattle bagworm infestations, [3] but since then the preference has shifted to the bacterial insecticide BTK. For small infestations or localized impact, "manual control"—simply picking bags from the trees—may be satisfactory.

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Codling moth species of insect

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Lackey moth species of insect

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<i>Apterona helicoidella</i> species of insect

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<i>Liothula omnivora</i> species of insect

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  1. Skaife, S. H., "African Insect Life", Pub. Longmans, Green & Co., London, 1953.
  2. Annecke, D. R. (1982). Insects and mites of cultivated plants in South Africa. London: Butterworths. ISBN   0-409-08398-4.
  3. Smit, Bernard, "Insects in South Africa: How to Control them", Pub: Oxford University Press, Cape Town, 1964.