Lacewings are familiar to many hobby gardeners because the insects are used in natural pest control. However, the animals have many secrets. Their life cycle is just as exciting as their food spectrum. Lacewings are by no means boring, as they have even developed special communication techniques.
Beneficial or harmful?
Lacewings are considered beneficial insects in both agriculture and forestry. They are bred in large numbers because of their importance in biological pest control. The larvae of lacewings help against aphids because they feed mainly on plant pests and are therefore called aphid lions. However, they are not picky and hunt for spider mites, mealybugs, thrips, whiteflies or other small insects.
Are lacewings dangerous?
Larvae have pincer-like mouthparts with which they grasp their prey. There are observations that the larvae also bite humans. Itching and inflammation may occur at the bite site. It is still unclear why the animals hunt humans. Researchers suspect that the larvae suffer from a lack of food during long dry periods and expand their prey pattern. Bites are also possible as a result of defensive reactions.
Most lacewing species no longer display a predatory lifestyle in the adult stage. There is no evidence that humans have been stung by adult lacewings in the past. Their mouthparts are used to pierce plant tissue and suck out the juice. It is of no use to them to pierce human skin. Lacewings are not poisonous and are therefore classified as harmless.
Distribution and habitat
lacewings occur worldwide. The common lacewing occurs both in lowlands and at higher altitudes. From spring to autumn it lives in the low vegetation of open fields and meadows. It prefers habitats with species-rich plant growth. Old deciduous trees serve as wintering grounds.
In house and apartment
When winter is just around the corner, lacewings seek out suitable crevices to overwinter. This means they get into apartments and houses. During the cold season the animals may be disturbed by light sources. After short flights around the apartment, the animals quickly crawl back into their hiding place.
Food
The majority of all lacewings feed on nectar, pollen and honeydew in the adult stage. Almost all larvae are predatory, as are the species of the genus Chrysopa. They hunt for smaller insects such as aphids or mites. If there is a lack of food, the larvae hunt larger organisms such as ladybird larvae. Even conspecifics are not spared.
Larvae eat large quantities of insects, although there is varying information about the exact number. These range from 150 insects within one development to 100 prey per day.
Profile
Lacewings are a family within the netwings, also known as goldeneyes. The species received this nickname because of the metallic-bronze shine of the compound eyes of some species. There are a total of around 2,000 different species, 70 of which occur in Europe. 35 species are considered native to Central Europe. The common lacewing (Chrysoperla carnea) is the best-known species. The family was named after the net-like wing pattern, which is also known as flor.
Excursus
A look into the taxonomy
Strictly speaking, Chrysoperla carnea is not a single species but a complete aggregate of several small species. Researchers came to this conclusion based on the advertising songs that the insects produce with their abdomens during mating season. However, the exact identification of the species is extremely difficult because the advertising songs sometimes seem to differ between individuals that look the same.
Features
The most striking feature of lacewings, which distinguishes all netwings, are the downwardly curved wings. They do not have a widened pronotum. In lacewings, this front body segment bends laterally up to the front legs. Lacewings differ from other netwings in the pattern of their transparent wings. The wings are rarely spotted or have markings. Central European species are predominantly green or brownish in color. They differ in their head markings.
wingspan of lacewings:
- Central European species: six to 35 millimeters
- tropical species: more than 65 millimeters
The lacewing is a very beautiful, delicate insect
Larvae
Lacewing larvae have an elongated body, the sides of which are covered with weakly developed tubercles. There are some species whose larvae have a squat body and are equipped with hook-shaped bristles. This hair serves as camouflage by allowing various materials or prey remains to stick to it.
Lifestyle and development
Lacewings are active during dusk or at night. They can communicate with other animals by vibrating their abdomen. This touches a surface, which in most cases is a leaf. Species in the genus Chrysopa respond to ultrasound by folding their wings to their bodies and falling to the ground. This behavior is a protection against natural enemies such as bats, which detect their prey using ultrasound.
Egg laying
Females lay their eggs individually on stalks that are up to ten millimeters long. In this way, a female can attach between 100 and 900 eggs to suitable locations. They choose places where the larvae are well cared for. Females therefore prefer aphid colonies as a place to lay their eggs.
Larval development
The first molt of the larvae occurs immediately after hatching. They then move around the plant to find food. Your mode of movement appears aimless. The larvae tilt their heads in all directions until their jaws come into contact with a prey animal. The contact triggers a stimulus that causes the larvae to grab hold.
They lift the prey with their mouthparts and inject a digestive secretion. This decomposes an aphid from the inside within 90 seconds and the larva can suck out the prey.
Lacewing larvae suck out aphids
Life expectancy
Depending on the environmental conditions, the development of the larva takes between eight and 22 days. Temperatures between 20 and 26 degrees Celsius favor larval development. Normally, the life expectancy of a lacewing is two to three months. The common lacewing is able to overwinter. She can reach an age of eight months.
Wintering
Central European species overwinter in a prepupal stage, which they spend in a double-walled cocoon. Only the common lacewing overwinters as an adult insect. To prepare for winter, it changes color from green to brown between September and October. Your metabolism is severely reduced. It does not survive the winter in heated rooms. Natural enemies and temperatures that are too low increase the mortality rate, which is between 60 and 90 percent in winter.
Wintering quarters:
- under the tree bark
- cool roof trusses and apartments
- Niches in gazebos and barns
Species
Lacewings are difficult to tell apart. Most species have a greenish shimmering body and strikingly veined wings with green nerves. There are also brownish or black species.
Some lacewings are able to change their color throughout the year. Shades of green turn into light brown shortly before winter so that the animals are better camouflaged in nature. After overwintering next spring, the animals turn green again. The habitat can also provide an indication of the species.
| Coloring | habitat | |
|---|---|---|
| Common lacewing | green and brown | warm mixed deciduous forests |
| Mediterranean lacewing | green all year round | Pine or pine forests |
| Red-headed lacewing | dark brown with red head | warm mixed deciduous forests |
The red-headed lacewing is characterized by its red head
Do lacewings need to be controlled?
Lacewings are extremely useful insects and should not be controlled. Reports of biting larvae are rare and do not reflect the animals' typical lifestyle. Lacewings do not normally become a nuisance because their populations are contained by natural weather conditions and predators.
Tip
If you spot an overwintering lacewing, it is best not to disturb the animal. In spring you can give the insect free flight by opening windows and doors.
Promoting lacewings
In the 1980s, intensive studies were carried out at the University of Bonn that examined the suitability of different winter quarters for lacewings. The experiments showed that lacewings are attracted to red and brown colors. The insects preferred models with a side length of 30 x 30 x 30 centimeters that were filled with straw. In such quarters, the mortality rate could be reduced to five to eight percent during the winter. The nesting boxes are also populated by ladybird larvae.
Buy insect hotel
It turns out that the majority of models on the market are not used by lacewings. If you decide to buy an insect hotel, you should pay attention to the minimum dimensions, structure, paint and interior design. Don't let the price alone entice you to order. High-quality models that are actually suitable as winter quarters for lacewings are not cheap. There are some variants made of wood concrete, the front of which has slats. These nesting boxes are well suited.
Build nesting aid
If you want to encourage lacewings in your garden, you can build your own insect hotel using the following building instructions. If you paint the wood in dark red tones, you increase the chance of successful use. When choosing colors, make sure that they are harmless to people, animals and the environment.
Construction instructions
Saw three panels measuring 30 x 30 centimeters. These act as back and side walls. The roof panel should protrude slightly so that no rainwater can run into the front opening. Plan about 32 x 30 centimeters for the roof. So that the box offers optimal protection from the cold, it should be made of solid wood.
Both the front and bottom of the box have slats that point downwards at an angle, reducing air circulation. You can saw the slats out of wood yourself. These should be about one centimeter wide and are attached to the two edges of the side walls. Use small spacers so that the slats lie at an angle. Wooden dowels are suitable for this and can be pushed between the slats and the edge of the side wall.
Filling
So that the hibernating insects are optimally protected from the cold, the insect hotel should be filled with natural materials. It turns out that lacewings like to overwinter in straw. In nature they also seek out piles of leaves or hide under the bark. To prevent the filling material from falling out of the box, you should cover the front and bottom with a fine-mesh wire mesh before attaching the slats.
Tip
Attach the roof to a hinge so you can open the box again. Regular cleaning is not necessary. You can replace the old filling material after about four years.
Hanging tips
The location plays a crucial role in ensuring that lacewings accept the winter quarters. Hang the box at a height of 1.5 to two meters. A tree that stands alone is ideal. You can also attach the shelter to a post or wall. Alignment is important. The front should face south so that the sun's rays warm the box. At the same time, the entry opening should not face the main wind direction.
Natural garden
Create a natural biotope in which lacewings automatically feel comfortable. The ideal habitat offers species-rich flower meadows that provide numerous nectar sources. Dead wood creates optimal quarters for overwintering. In large gardens, it is recommended to plant shrubs and deciduous trees.
Wild plants in pots
If you only have little space in the garden, you can fill flower boxes and pots with wild plants. A self-built insect hotel provides the perfect retreat. Leave leaves lying around in autumn and avoid using chemical pesticides. In a structurally rich natural garden, the insects find natural hiding places. You also support numerous specialized insect and bird species that complete the local biotope.
Plant list
Catnip is attractive to lacewings, as studies by American researchers have shown. The flowers of catnip produce nepetalactone. This fragrance is similar in composition to the sexual attractant of adult lacewings. At the same time, nepetalactone has antimicrobial and antiviral properties. Catnip attracts beneficial insects and repels numerous plant pests such as mosquitoes, cockroaches and fleas. The fragrance is also produced by aphids. Purple coneflowers and nectar-rich late summer bloomers are also attractive to lacewings.
Lacewings are magically attracted to catnip. This is impressive because the plant deters many pests.
Breed and use
There are now specialist companies that are also involved in breeding lacewings. There are breeding sets with larvae and food that are intended for private use. However, breeding requires some patience and consistent attention so that the larvae develop into adult insects. If your plants suffer from an aphid infestation, larvae are an effective control method.
Application in the apartment
Lacewing larvae are sent by post in cardboard honeycombs or on buckwheat husks. Both variants prevent the larvae from eating their fellow species. To ensure that they do not freeze, they are only shipped during the frost-free period. You can also order lacewings in the egg stage. These are delivered loose or glued to a cardboard box. Under optimal conditions, it takes around four to six days for the larvae to hatch. If the larvae hatch during shipping, there is a higher risk of cannibalism.
Benefits of Pest Control with Lacewings:
- Larvae are active at temperatures as low as ten degrees Celsius
- good results are achieved even at low humidity
- Activity of the larvae is independent of light intensity and day length
Frequently asked questions
How long does a lacewing live?
Lacewings go through several larval stages, which usually last two to three weeks. They stop eating shortly before pupation. They then spin themselves into an oval cocoon in which they spend the next ten to 30 days, depending on the temperature. The adult lacewing begins laying eggs when it is four to ten days old. She has a life expectancy of about two months. Overwintering insects can live up to eight months.
Why do lacewings lay their eggs on stalks?
This behavior is intended to protect the larvae from cannibalism. A female can lay between 100 and 900 eggs this way. The eggs are initially colored green. They then turn from dark green to brown. Shortly before hatching they are colored grey-brown.
Is a lacewing bite dangerous?
Usually there is no danger for people or pets of being bitten by a lacewing. There are reports that the larvae have bitten into human skin. Such a bite can cause inflammation and itching. The symptoms automatically subside after a few days. This behavior is not typical. Researchers suspect a lack of food as the trigger.
What to do against lacewings in the apartment?
The insects get lost in buildings when they are looking for suitable winter quarters. They like to retreat into unheated rooms and use niches and cracks as a place to retreat.
In winter they can be disturbed by light sources, causing them to fly around the room. After a short time they retreat again. Since these are beneficial insects, you should not fight them. Give them a safe place to overwinter, because around 60 to 90 percent of all overwintering lacewings do not survive the winter.
How can I attract lacewings?
The insects like a natural garden that offers small-scale structures. Flower-rich borders with plants that produce nectar are important. Woody plants and deciduous trees serve as wintering grounds. Plant catnip and coneflowers. Catnip in particular is a popular flowering plant among lacewings because its scents are similar to sexual attractants.
