fly

fly

This data is reviewed by the project of data compilation and application of Science Encyclopedia of science popularization in China.

The life history of flies can be divided into three stages: egg, larva, prepupa, pupa and adult. Although the life span of flies is only about one month, they have strong fecundity. The feeding habits of flies are very complex, belonging to omnivorous flies, which can feed on various substances.

Biological characteristics

Flies are small to medium-sized, with short antennae and only three nodes. There is a flagellum at the end of the terminal node or a feather on the back of the terminal node, which is called arista. There were 2 compound eyes and 3 monocular eyes. The mouthparts are licking sucking. Forewing membranous, used for flight. The hind wing degenerates into a halter, hidden under the wing flap at the base of the forewing.

The lower lip degenerates into a long beak, and the end of the beak expands into a pair of lip petals with ring grooves. There is a sword shaped upper lip at the base of the back of the beak, which is close to a long flat tongue and forms a food passage.

Characteristics of the foot

First of all, flies have a set of skills to walk on six feet. The left and right sides of the fly's body, the front and back feet of each side and the middle foot of the opposite side form a "triangle", a total of two "triangles". When the first "triangle" is lifted and stepped forward, the other "triangle" supports the body and maintains the balance of the body. In this way, flies can not only walk on uneven objects, but also create conditions for crawling on swinging objects.

Secondly, the fly has a pair of claws and pads at the end of each foot. The claw like pincers, coupled with the cooperation of the steel and hard foot hair, can easily clamp the object and support the body, and when the foot is lifted, it can automatically release the object; the fat claw pad has glands and fine hairs like a brush, and the lipid liquid secreted by the glands can not only keep the fine hairs on the claw pad moist and not brittle, but also increase the contact area and adhesion between the foot and the attachment Strong. The area of hind paw pad is larger than that of forefoot, and the adhesion is stronger.

Thirdly, the adhesive force is not only related to the contact area, but also to the number of feet. The results showed that the fly with an average weight of 0.07g consumed 0.00103n for vertical takeoff and 0.0024n for six legs.

Because of the above reasons, flies can not only walk on the plane, but also walk freely on the swinging objects and smooth windows, and even crawl upside down on the ceiling without falling down due to gravity.

Ecological habits

mating

A female fly can lay eggs 5-6 times in a lifetime, with about 100-150 eggs per time, and about 300 eggs at most. It can reproduce 10-12 generations in one year. Under suitable temperature, male housefly can mature and mate 18-24 hours after eclosion and female housefly can mate 30 hours after eclosion. Mating time is usually between 5:00 and 7:00 in the morning. Sensitive sense of smell, sex hormone and vision are important factors to promote the mating of male and female flies. A pair of mating houseflies can stay in one place for a long time, crawl together and fly together. The effective mating time is up to 1 hour. Most houseflies mate only once in their lives. The semen of the male fly can be stored in the seminal vesicle of the female fly for a long time to stimulate the oviposition of the female fly, and it can continue to fertilize the eggs for 2-3 weeks without mating with another male fly. This is rare among other insects. This is an important reason why flies have high fecundity.

lay eggs

The peak time of oviposition is from 17:00 to 19:00 every day. The duration of pre oviposition (that is, the time from eclosion to the first oviposition) of female flies is closely related to the environmental temperature: the average time is 9 days at 15 ℃, only 1.8 days at 35 ℃, and no oviposition below 15 ℃. After mating, the female flies often crawl into the breeding gap of human and animal feces, extend the oviposition tube and lay eggs in the breeding depth, so as to fully protect the eggs.

Flies have amazing fecundity. According to the observation, each batch of houseflies in the laboratory laid about 100 eggs, and one female finally laid eggs

living

It can lay 10 ~ 20 batches of eggs, and the total number of eggs is 600 ~ 1000. In nature, each female fly can lay 4-6 batches of eggs in its lifetime, with an interval of 3-4 days. The number of eggs laid in each batch is about 100, and the final number of eggs produced is 400-600. Even in North China, houseflies can reproduce 10-12 generations a year. According to the most conservative estimate, each female can produce 200 offspring, so the total number of houseflies will reach 2 trillion after 10 generations of 100 females!

Food habit

The feeding habits of flies depend on their species. There are those who specially suck nectar and plant juice, and those who specially eat human or animal blood or animal wound blood and eye or nasal secretions. The common housefly, Chrysomyia megacephala, Lucilia sericata, Calliphora and Lepidoptera belong to omnivorous flies, which widely ingest human food, livestock and poultry secretions and excreta, kitchen waste and organic matter in garbage. They have a strong tendency to sugar, vinegar, ammonia and fishy smell. According to the research, if the female flies only supply water, sugar and carbohydrate, they can grow, but their ovaries can't develop and lay eggs; they can lay eggs only if they are fed with protein or multiple amino acids. If royal jelly is used to feed female housefly, the pre oviposition period can be shortened and the oviposition quantity can be increased.

The fly's food habit is very miscellaneous. It likes fragrance, sweetness, sour and stink. When it feeds, it has to spit out crop liquid to dissolve food. Its habit is to eat, spit and pull at the same time. It has been observed that flies defecate 4-5 times per minute when food is abundant.

Flies will eat harmful bacteria while eating, so the method of "spitting while eating" is helpful to eliminate bacteria quickly. In general, it takes only 7-11 seconds for flies to feed, process, absorb nutrients and discharge wastes. When it comes to bacteria with rapid propagation ability, the immune system of flies will emit bf64 and BD2 globulins. Once it comes into contact with bacteria, it will "explode" and "die together" with bacteria. The firing of these two globulins is always one in front of the other in pairs.

It is worth noting that the bactericidal ability of bf64 and BD2 is thousands of times stronger than that of penicillin. If bf64 and BD2 can be extracted from flies and used to treat human diseases, it will bring good news to human beings.

Activity characteristics

Flies are insects that move frequently in the daytime and have obvious phototaxis. At night, it is still. Activity and habitat depend on species, season, temperature and region. In some seasons, the house fly, summer fly and City fly also invade the house. Chrysomyia megacephala, Chrysomyia sericata, Calliphora viridis, Chrysomyia volvacea and Lepidoptera Lepidoptera mainly live outdoors.

The activity of flies is greatly affected by temperature. It can only crawl at 4-7 ℃, fly at 10-15 ℃, feed, mate and lay eggs at above 20 ℃. It is especially active at 30-35 ℃. It stops activity at 35-40 ℃ due to overheating and dies at 45-47 ℃.

Flies are good at flying. The flight speed can reach 6-8km per hour, and the maximum is 8-18km per day and night. However, they usually live within the radius of 100-200m, mostly less than 1-2km.

Flight characteristics of take-off: during the start-up stage of take-off, the fly always jumps through the "pedal" action of midfoot and hindfoot, and leaves the ground and spreads its wings in 0.03 seconds. The angle between the fly's flight path and the ground is often less than 40 degrees. Only in very occasional cases can the fly have a nearly vertical take-off angle, but it will turn to an inclination angle 10 mm above the ground.

The way flies overwinter is quite complicated. It can overwinter as pupa, maggot and adult. In the northern cold and temperate regions, there are no living flies in nature, but there are still adult flies in the artificial heating room. Vegetable greenhouses often become the birthplace of a large number of flies when the next spring is warm. In Jiangnan and part of North China, when the average temperature is below 0 ℃, flies can live through the winter as pupae skillfully. Dormant female flies and maggots covered with livestock manure can also be found in a few areas. In the south subtropical region of China, when the average temperature is above 5 ℃, flies do not exist dormancy and can continue to breed.

Life course

The pupal development of the fly takes only 3 to 6 days from the pupal stage. In a few days to more than ten days, the granular eggs grow into flies.

Adults begin to move and eat 2 to 24 hours after eclosion. Flies can mate and lay eggs only after feeding. Flies are very good at flying and have phototaxis. They fly wherever it is bright, so they like to move in places with lights during the day or at night. In dark places or at night, they stop on the ceiling or the hanging ropes and walls to rest.

Flies can mate 1-2 days after eclosion, and produce small piles of eggs a few days after mating. Flies are different from other animals. Most animals mate only when they are in oestrus, and mate once to produce offspring. Flies are much less likely to mate once in their lives. A single mating is enough for female flies to produce fertilized eggs all their lives. Even if the male flies are dead, it doesn't matter. As long as the mated female flies are alive, it doesn't affect their breeding batch after batch of flies, and it doesn't affect the survival of the next generation

Chinese PinYin : Cang Ying