Are the dragonflies, crickets, longhorn beetles, and seven-spot ladybugs commonly seen in rural areas beneficial insects or pests?
In rural areas, you will often see dragonflies, crickets, longhorn beetles, and ladybugs, but few people have really thought about one question: are they beneficial insects or pests to humans? In the entire insect ecosystem, there is actually no distinction between beneficial insects and pests. These two words are purely definitions produced from the human perspective. Generally speaking, those beneficial to humans are beneficial insects, and the opposite are pests.
1. Dragonfly
The dragonfly is a typical hemimetabolous insect, divided into the two families Libellulidae and Aeshnidae. In the stage of transformation from nymph to adult, it does not need to go through the process of forming a pupa. In its lifetime it experiences only three stages: egg, nymph, and adult. The nymph is aquatic, while the adult is a terrestrial insect with flight capability.
Is the dragonfly a beneficial insect or a pest?
Whether the dragonfly is beneficial or harmful must be viewed by stage. In the larval stage, the dragonfly, that is, the nymph, lives on small fish and tadpoles. It is very fierce and is a pest of farmed fish, especially in the breeding of fry and the farming of tropical fish, where it must be completely removed.
After maturing and emerging, the beautiful dragonfly is a greatly beneficial insect, feeding on pests such as flies, mosquitoes, and moths. They are almost born specifically to catch pests and are of great help to human life. They are not only good for human health, but also play a great role in the abundant production of farmland crops.
The dragonfly's food intake is also very astonishing. It belongs to the carnivorous insects and specifically uses mosquitoes, flies, and other small insects as food. A large green dragonfly commonly known as the “green-headed dragonfly” can carelessly eat around two thousand small flying insects such as aphids in a day. It goes without saying that it eats mosquitoes and flies; in addition, it welcomes any small moth or small insect that can fly or crawl. Eliminating pests for humans in such large numbers, it fully deserves to be called a “beneficial insect.”
How long can a dragonfly live?
The dragonfly's larval stage, the nymph, must spend at least one year in the water. The total time required for the larval stage varies according to different species and seasons, ranging from one month to three or four years, and the longer ones must endure seven or eight years before they can emerge as adults. The lifespan of the adult dragonfly is only one tenth that of the larva, living only about one month to eight months. Even so, among insects the dragonfly still counts as long-lived.
2. Cricket
The scientific name of the cricket is ququ. It is an invertebrate animal of the family Gryllidae in the order Orthoptera of the class Insecta. It does not sing, but the male can produce sound by rubbing its wings. Its distribution range is extremely wide, and it is found almost everywhere across the country. Male crickets are aggressive, so people like to keep them for viewing and cricket fighting.
Is the cricket a beneficial insect or a pest?
The cricket is a pest. Crickets are an important agricultural pest in Northeast China, North China, the lower reaches of the Yangtze River, and South China. They destroy the roots, stems, leaves, fruits, and seeds of various crops, and cause especially serious damage to seedlings. In the south, peanut seedlings damaged by crickets reach 11 to 30%. They also harm corn, jute, tobacco, cotton, soybeans, and cassava, often causing missing plants and affecting the harvest.
What food do crickets eat?
Crickets living in the wild generally feed on tender buds, tender leaves, and roots, while crickets kept by people are given not only various fresh vegetables and fruits, but keepers also choose some foods and mix them in proportion to make a rich, nutritious meal. Feeding them regularly and in fixed amounts every day prompts the crickets to grow healthier and fiercer.
3. Longhorn beetle
The longhorn beetle is the general name for insects of the family Cerambycidae in the suborder Polyphaga of the order Coleoptera. It has chewing mouthparts and very long antennae, often exceeding the length of the body. There are about more than 20,000 species worldwide. Both larvae and adults mostly prefer to be active on trees, such as mulberry, willow, poplar, citrus, and pine, all of which have many kinds of longhorn beetles reproducing on them.
Is the longhorn beetle a beneficial insect or a pest?
The longhorn beetle is a major pest in forestry production, crop cultivation, and building timber. Longhorn beetles are mainly pests of woody plants, and in the larval stage they bore into trunks, branches, and roots. Some harm herbaceous plants, with larvae living in stems or roots, such as the chrysanthemum longhorn beetle and the melon vine longhorn beetle. A few species, such as the cotton boll longhorn beetle, harm cotton bolls. There are also a small number of species whose larvae do not live in plant tissues but instead feed on roots in the soil, such as the large-toothed and curved-toothed sawyer longhorn beetles, grass longhorn beetles, and so on.
What do longhorn beetles eat?
Longhorn beetles are phytophagous insects, and they are known to have different habits of feeding on pollen, tender bark, tender twigs, leaves, roots, tree sap, fruits, fungi, and so on. Flower longhorn beetles often feed on pollen, while grooved-tibia longhorn beetles often feed on and damage tender bark, tender twigs, and leaves. Longhorn beetles are major pests in forestry production, crop cultivation, and building timber, harming most pine, cypress, willow, elm, walnut, citrus, apple, peach, and tea, some cotton, wheat, corn, sorghum, sugarcane, and hemp, and a few timber, buildings, houses, and furniture, and so on.
4. Ladybug
The ladybug is the general name for round, convex beetles of the family Coccinellidae in the order Coleoptera. Their body colors are bright, often with red, black, or yellow spots. They are also called pangxiao, hongniang, huadajie, jingui, and so on, and because the secretions of some species have a foul odor, they are even commonly called stink beetles. In their lifetime they go through the four stages of complete development: egg, larva, pupa, and adult.
Is the ladybug a beneficial insect or a pest?
Among ladybugs there are both pests and beneficial insects. There are very many kinds of ladybugs, and by feeding habit they can be divided into carnivorous ladybugs and phytophagous ladybugs. Adult carnivorous ladybugs prey on any soft, tender insect and most like to eat aphids, such as the seven-spot ladybug. Most species of phytophagous ladybugs feed on plants of the Solanaceae, Cucurbitaceae, and Asteraceae families, such as the potato ladybug and the 28-spotted ladybug, which collectively eat the leaves of eggplant and potato and are therefore regarded as pests.
Which ladybugs are pests?
1. 28-spotted ladybug: The host plants of the 28-spotted ladybug are Solanaceae vegetables such as potato, eggplant, tomato, and green pepper, and Cucurbitaceae vegetables such as cucumber, winter melon, and loofah. In addition, it also harms beans, black nightshade, Chinese lantern, datura, tobacco, and so on. Adults and larvae eat the leaf mesophyll, leaving the upper epidermis in a net-like pattern, and in severe cases eat the entire leaf. In addition, they also feed on the surface of melons and fruits, and the damaged parts become hard and carry a bitter taste, affecting yield and quality.
2. Ten-spotted ladybug: Both adults and larvae of the ten-spotted ladybug feed on leaves, making the leaves appear holed or notched, or eating the leaves completely and leaving only the veins. After the larvae mature, they bore into the soil to build a chamber and pupate. After the adults emerge, they move to the host to cause damage, mainly feeding on plants such as grapes, wild grapes, and five-leaved cayratia.
3. Potato ladybug: Adults and larvae of the potato ladybug peel and eat the leaf mesophyll on the underside of leaves, leaving only the epidermis and forming many irregular, translucent, fine grooves, like the bottom of a basket. They can also eat the leaves into holes, or even leave only the veins. In severe cases, the damaged leaves dry up and turn brown, and the whole plant dies. The parts of the fruit that are gnawed often split, and the tissue becomes stiff, rough, and bitter, making it inedible.
Which ladybugs are beneficial insects?
1. Seven-spot ladybug: The seven-spot ladybug is a beneficial insect. Adults can prey on pests such as wheat aphids, cotton aphids, locust aphids, peach aphids, scale insects, and mites, and can greatly reduce the damage suffered by trees, melons and fruits, and various crops from pests. It is called a “living pesticide” by people and is widely distributed across various parts of China.
2. Harmonia axyridis: In addition to preying on cotton aphids, adults and larvae of Harmonia axyridis can also prey on the eggs and young larvae of cotton bollworm. The maximum daily average predation by adults is around 70 cotton bollworm eggs; larvae were not seen preying on cotton bollworm eggs. For newly hatched cotton bollworm larvae, adults prey on 70 and fourth-instar larvae on 69.
3. Six-striped ladybug: The six-striped ladybug is also called the six-spotted ladybird. The larvae are black in body color, with white longitudinal spots in the center of the back, and feed on many kinds of aphids. Adult spot patterns vary in more than 20 forms, but the markings on the pronotum are relatively stable. It is generally distributed from flat ground to low-altitude mountain areas, commonly active on plants with aphids, and can be seen year-round.
4. Propylaea japonica: Propylaea japonica is a beneficial insect and preys on aphids, leafhoppers, planthoppers, and so on. In cotton fields in July and August, it preys on summer aphids, cotton bollworms, and the eggs and young nymphs or larvae of other pests. At the same time, July to September is also an important natural enemy in orchards, feeding on pests such as aphids, leafhoppers, and planthoppers in apple orchards.
5. Synonycha grandis: Adults of Synonycha grandis have a body length of 0.8 to 17 mm, with an oval or long oval outline, a hemispherical dorsal surface, and a flat ventral surface. They are rare in number and prey on scale insects, and both adults and larvae prey on sugarcane woolly aphids. They are distributed in Guangxi, Fujian, Taiwan, China, Guangdong, Guizhou, Yunnan, and other places.
6. Australian ladybug: The Australian ladybug is an agricultural beneficial insect, native to Australia. It prefers shaded environments and has a death-feigning habit. When newly hatched, it often concentrates on feeding on female adult cottony cushion scale, and later gradually disperses. At present, more than 50 countries have introduced the Australian ladybug to control cottony cushion scale. China began introducing it in 1955 for research and use, effectively controlling the occurrence of cottony cushion scale, and it is known to be distributed in the citrus-producing areas of the south.
What food does the seven-spot ladybug eat?
The seven-spot ladybug is a beneficial insect. Adults can prey on pests such as wheat aphids, cotton aphids, locust aphids, peach aphids, scale insects, and mites, and can greatly reduce the damage suffered by trees, melons and fruits, and various crops from pests. It is called a “living pesticide” by people, is non-toxic and harmless to humans, livestock, and natural enemy animals, leaves no residue, and does not pollute the environment.