Biological observation of the silk wool wood Venus ruler moth
Abstract: The silk cotton wood Venus ruler moth is a major pest on the white du wei spear, which can eat all the leaves and young branches when seriously endangered, resulting in the death of the whole plant [1-6]. The silk wool wood Venus ruler moth was collected from the BaiduWei spear tree in the West Peak District, and after rearing observation, its eggs were block-laid, ranging from 34-186 per piece, and the single egg was oval. The larvae are 2–32 mm long, black, and have seven blue-and-white longitudinal lines on their backs. Pupae overwinter in masonry tiles or soil under the canopy and are dark red in color. Adults are 11–14 mm long , with grey and yellowish-brown markings on the wings , and are sunrise-like. The effective accumulated temperature required for the larval stage is 306.47 days. Three generations occur a year in the Xifeng District, and the third generation is the most harmful.
Keywords: observation; white du wei spear; silk wool wood Venus ruler moth; morphological characteristics; occurrence law;
The silk woolly Venus ruler moth belongs to the order Lepidoptera, in the family Ulmus. Distributed in North China, Central South China, East China, North China, Northwest China, Northeast China and other places. It is hosted in silk cottonwood, large-leaved boxwood, and fufang vine. Leaf-eating pests, often outbreaks, will eat all the leaves in a short period of time [1]. In the autumn of 2012, after observation, the harm rate of the silk wool wood Venus ruler moth on the Weimao tree in Xifeng District reached more than 90%, the degree of harm was serious, and the leaves of each tree were seriously damaged, resulting in shrinking of the canopy and drying up branches in winter, see Figure 1. If it is not protected and controlled by insect pests, it will not only affect ornamentation, lose economic value, but also cause a lack of biodiversity. Observe and study the biological characteristics and laws of the silk wool wood Venus ruler moth, explore the key links, and provide basic materials for experimental teaching and control work.
1 material method
1.1 Materials
Insect source: Longdong University Botanical Garden, three White Du Wei spear tree excavation of soil blocks, its length of 30 cm wide 30 cm depth of 10 cm, the collection of overwintering insect pupae, placed in a carton, covered with soil sprinklers, simulated natural conditions for breeding. In the garden, the white duwei spear tree collects eggs and leaves to hatch and raise.
Feed: White Du Wei spear blades
1.2 Feeding and methods
After feathering, it was placed in a carton with a length of 25 cm and a width of 25 cm and a height of 10 cm for pairing observation, and at the bottom of the carton, the white duwei spear belt leaf branches were placed for it to lay eggs. Replace the eggless leaves regularly after spawning to keep the feeding leaves fresh, observe the records, and wait for natural hatching. After incubation, the leaves are changed regularly, reared in a carton, and the records are observed.
2 Observation of biological characteristics
2.1 Biological characteristics of eggs
The silk wool wood Venus ruler moth is a mass-laying, arranged in strips on the leaves, ranging from dozens to hundreds of grains. It is more prolific on the back of the leaf, and the individual eggs are oval in shape, about 0.8 mm long and 0.6 mm wide, and have a longitudinal pattern on the surface of the egg shell. It is lighter in color at first birth, fading bluish-gray and dark brown near hatching. The same egg can hatch within a day. The eggs laid on the back of the leaves of the silk wool wood Venus ruler moth were photographed, as shown in Figure 2.
2.2 Biological characteristics of larvae
2.2.1 Observational studies of larvae at various ages
The first-instar larvae move quickly after hatching and can crawl quickly to the young leaves for feeding. In hatching, the middle of the egg blocks first hatches, then gradually spreads around, disperses and feeds on the leaves. The state of the silk wool wood Venus ruler moth when hatching is shown in Figure 3.
The newly hatched larvae, 2-3 mm long, have a black-brown head, a reddish front half of the body, a translucent back half, and a faster movement, see Figure 4. After feeding on the leaves, the head is black, the body color gradually turns green, and the first-instar larvae only feed on the back of the leaf when feeding, leaving the front epidermis of the leaf after feeding. Take images of newly hatched larvae after feeding, see Figure 5.
After the larva hatches, after 4 days of rearing, it begins to molt for the first time, the length before molting is 3-4mm, the head is black, the molting begins from the head, the larva no longer eats when molting, and all molts are completed after 1 day. After molting and feeding, the larvae are dark green, the head is black, and the length is 4-5 mm. After the 3rd age, the body color deepens and turns black, and the 5 white lines of the dorsal midline, sub-dorsal line and valve line are clearly visible. And the amount of food increased rapidly, the larvae ate the leaves into missing holes, leaving only the leaf veins, and biting off the young shoots, and in severe cases, together with the leaf veins, only the bald branches were left. The inner leaf larvae are more distributed, and once shaken, the larvae will spit silk down or float in the air.
The mature larvae are 28–32 mm long and black, the bristles are yellowish brown, the head is black, the crown and share slits are pale yellow, and the dorsal plate of the forebreast is yellow, with three black spots, and the middle is triangular. The dorsal line, subsodoral line, valve line, and sub-abdominal line are blue-white, and there are yellow horizontal stripes on the thorax and sections after the 6th section of the abdomen. The thorax and feet are black and the base is yellowish. The ventral toe hook is a double sequence middle band [2]. A static picture of the old mature larvae is shown in Figure 6.
2.2.2 Effective accumulation of temperature in each age of larvae
The reared silk wool wood Venus ruler moth is observed once a day in the morning, middle and evening, the current insect state is recorded, and the maximum temperature and minimum temperature of the day are recorded, and the table is arranged, the relationship between the changes of each age and the temperature is analyzed, and the effective accumulated temperature corresponding to each age is calculated, and the detailed data are shown in the attached table. The analysis results are counted in the following table.
Table 1 Relationship between ages and temperature of larvae of the Silk Woolly Wood Venus ruler moth
As can be seen from the above table, the larvae of the silk cotton wood Venus ruler moth have a total of 5 years and last for 30 days. The length of age varies depending on the age, and the required effective accumulated temperature also changes. With the increase of age, the effective accumulated temperature required for each age gradually increases, and the length of age also gradually increases. The effective accumulated temperature required for the larval stage of the silk cotton wood Venus ruler moth is 306.47 days. Its developmental temperature (biological zero degrees) is 9 °C. In the calculation process, the daily average temperature is calculated by the extreme value method, and due to the limitation of observation conditions, the developmental temperature is calculated according to its approximate value, that is, the minimum temperature of the larval stage. Detailed data are provided in Schedule 1.
2.3 Pupal morphological observation
The silk woolly Venus ruler moth pupa is a naked pupae, 9–14 mm long and 3.5–5.0 mm wide, dark red, with a forked rump spine at the ventral end. The outline of part of the organs of the adult worm can be observed on the surface of the pupae. 85 pupae were collected, the excavation surface was 2700 square centimeters, and the density of insect pupae under the White DuWei spear tree on the campus was calculated to be 315 /㎡. The density of insect pupae is large and the pupae are concentrated, indicating that the previous year's occurrence period is seriously harmful and easy to accumulate in the same place. Photograph the morphology of the overwintering pupae, as detailed in Figure 7.
2.4 Morphological observation of feathered adults
Adults are 11–14 mm long and spread their wings 32–39 mm. Adult wings are silvery-white on the underside , with pale grey and yellowish-brown markings , and one row of continuous pale gray stripes on the outer margin of the forewings. The abdomen is yellow with black spots, the female has 9 rows of stripes consisting of black spots, and there is no clump hair on the inside of the hindpod embryonic segment. The male has 7 rows of stripes composed of black spots, and there is still a clump of yellow hair in the hind foot festival [3]. There is tenderness and light-seeking is weak. It often inhabits the branches and leaves of the canopy during the day, and on sunny and hot days under large trees or on shaded walls, it is a sunrise insect. Not good at flying. Images of adults after feathering of the silk woolly wood Venus ruler moth were taken, as detailed in Figure 8.
3 Occurrence regularity
3.1 Generation
The silk wool wood Venus ruler moth occurs in Tianjin in three generations a year [4]. In the Anhui region, 4 generations occur a year [5]. In Dalian, 2 generations occur in one year [6]. In Shonan, 4 generations occur in a year [7]. Four generations a year occur in the Shanghai area [7]. Xifeng District occurs 3 to 4 generations a year.
3.2 years of life history
The silk wool wood Venus ruler moth overwinters in the soil under the masonry tiles in the west peak pupa. In mid-April of the following year, the adults feather and lay eggs on the back of the leaves, in a lumpy shape, ranging from a few to dozens of eggs per egg. In early May, the hatching of the first generation of larvae began, the hatching larvae spit silk drooped and migrated to the dorsal shade, dozens of larvae lived in groups on the back of the leaf to eat leaf flesh, leaving the leaf veins in a network, the larvae dispersed the hazard after 3 years, and entered the binge eating period after 5 years, feeding on the leaves and leaving only the main vein. After old maturity, it enters the soil to pupate, and the pupa feathers into adult worms after more than 10 days. Completed a generation of life history, the annual life history of the silk wool wood Venus ruler moth in the West Peak Area is shown in Table 2.
Table 2 Life history of the silk woolly wood Venus ruler moth
Note: ▽indicates egg; ▼ indicates larva; △ indicates pupae; ▲ indicates adult worm
Table 2 of the analysis shows that the silk wool wood Venus ruler moth occurs in 3 to 4 generations per year in the West Peak Area, and there is a phenomenon of generation overlap. The first generation is from late April to late June, the second generation is from late June to early September, the third generation is from late July to mid-October, and the fourth generation is from early September to mid-May of the following year. Moreover, it has been observed that the first and second generations occur less, usually belonging to the accumulation generation of insect sources, with the third generation being the most seriously harmful and the fourth generation occurring sporadically.
4 Conclusions
Through feeding observation and field investigation, the life law of the silk cotton wood Venus ruler moth is clear, and the biological characteristics of the silk cotton wood Venus ruler moth are analyzed and recorded on the basis of the existing results of the predecessors. Roots were found to be most harmful to the spear in the West Peak area, from late June to late September. Adult eggs are concentrated on the host leaf and prominently located. The age of the larvae is significantly affected by temperature, and it is easy to erupt early in years with higher temperatures. After 3 years of age, the amount of food larvae increases greatly, and the harm is aggravated. Old mature larvae have a habit of spitting and drooping. Mature larvae concentrate under the soil around the host tree, and the pupae are dense. Among them, new progress has been made in the study of the larval stage, which clarifies the effective accumulated temperature required for each age of the silk cotton and wood Venus ruler moth, the effective accumulated temperature required for the larval stage is 306.47 days, the developmental temperature is 9 °C (biological zero), and precious picture data are taken, filling the gap in related research. The life history of the silk cotton wood Venus ruler moth in xifeng district is recorded in detail, which can be used as a reference for the prevention and control of silk cotton wood venus ruler moth in xifeng district.
5 discussions
In the writing of this paper, some of the research content is not detailed and thorough, and the involvement is not comprehensive enough. The biological zero degree of its silk cotton wood Venus ruler moth is calculated according to the lowest temperature experienced during its reproductive period, and there is a certain error. The average daily temperature adopts the average temperature of the extremum (the average of the daily maximum and minimum temperature), and the resulting effective accumulated temperature value is incorrect with the actual value. Effective accumulation temperatures for adults and pupae have not been studied, and it is recommended that follow-up studies can address this aspect.
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Figures
Figure 1 Silk wool wood Venus ruler moth harm Baidu Wei spear diagram
Figure 2 Eggs of the leaf dorsal silk wool wood Venus ruler moth
Figure 3 Hatching status diagram of the silk wool wood Venus ruler moth
Fig. 4 Uneaten larvae have just hatched
Figure 5 After feeding of newly hatched larvae
Figure 6 Static diagram of the old mature larvae of the woolly wood Venus ruler moth
Figure 7 Morphological diagram of the overwintering pupae
Figure 8 Morphological pattern of the feathered adult moth of the silk wool wood Venus ruler moth
Schedule: Table of Observation Records