Chilo suppressalis insect source detection equipment

Abstract

The invention provides a chilo suppressalis insect source detection device which comprises an X-light ray source array, a light sensing plate, an objective table and a driving device, a horizontal detection chamber is defined by the light sensing plate, the X-light ray source array is horizontally arranged in the horizontal detection chamber, a detection space is formed by the objective table, and the X-light ray source array is arranged in the detection space. The objective table is arranged to be capable of keeping the rice straw horizontally contained in the detection space, and the X-ray source array is arranged to be capable of being driven to rotate around the detection space formed by the objective table.

Description

Technical Field

[0001] The present invention relates to crop pest control, and in particular to a striped stem borer source detection device capable of automatically and quickly detecting the number of striped stem borers in rice stalks. More specifically, the present invention relates to a striped stem borer source detector. Background Art

[0002] The Chilo suppressalis belongs to the order Lepidoptera, the family Pyralidae. It is one of the most serious common pests on rice in my country. During the tillering stage, it will cause rice sheath and heart dryness, and during the heading stage, it will cause rice insect damage and white ears. In general, it will reduce the yield by 3% to 5%, and in severe cases, it will reduce the yield by more than 30%. The Chilo suppressalis is distributed in all rice-growing areas in China, but it is mainly in the Yangtze River Basin and the rice-growing areas to the south. The degree of occurrence has shown a clear upward trend in recent years.

[0003] Accurate monitoring and forecasting of the source of the stem borer before and after overwintering in rice piles is of great significance for later prevention and control. It helps plant protection agencies guide farmers to take targeted prevention and control measures to improve the prevention and control effect, such as deciding whether to use winter stubble treatment based on the overwintering base number, and deciding the time and density of hanging traps based on the amount of residual insects and development progress after winter.

[0004] However, the current means of monitoring the source base of the Chilo suppressalis are relatively simple. Plant protection agencies often adopt random sampling in the fields, and conduct monitoring and statistics by manually peeling rice stalks and manually counting. Manual peeling requires completely peeling the rice stalks and completely breaking up the insect clusters in order to accurately count them. This is not only slow, but also easy to miss, consuming a lot of material, manpower and time, with low work efficiency and low accuracy. In addition, the monitoring and statistics by manually peeling rice stalks and manually counting also require the separate counting of live and dead insects, and the calculation of the proportion of dead or live insects to the total number of insects after entering the data, which is rather cumbersome. Summary of the invention

[0005] The main advantage of the present invention is to provide a rice stem borer source detector, which can automatically and quickly detect the number of rice stem borers in rice straw in a non-contact manner.

[0006] Other objects and features of the present invention will be fully apparent from the following detailed description.

[0007] According to one aspect of the present invention, a device for detecting a source of Chilo suppressalis of the present invention that can achieve the aforementioned objects and other objects and advantages comprises:

[0008] X-ray source array;

[0009] Photographic plates; and

[0010] The stage is provided with a photosensitive plate, wherein the photosensitive plate is arranged to form a horizontal detection chamber, the X-ray source array is arranged horizontally in the horizontal detection chamber, the stage forms a detection space, and the stage is arranged to keep the rice straw horizontally contained in the detection space, wherein the X-ray source array is arranged to be driven to rotate around the detection space formed by the stage.

[0011] Further objects and advantages of the present invention will be fully apparent from an understanding of the following description and the accompanying drawings.

[0012] These and other objects, features and advantages of the present invention will be more fully understood from the following detailed description and accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 Shown is a three-dimensional schematic diagram of a Chilo suppressalis source detector according to an embodiment of the present invention.

[0014] Figure 2 Shown is a three-dimensional schematic diagram of an insect source detection device of a Chilo suppressalis insect source detector according to an embodiment of the present invention.

[0015] Figure 3 Shown is another three-dimensional schematic diagram of the insect source detection device of the Chilo suppressalis insect source detector according to an embodiment of the present invention.

[0016] Figure 4 Shown is another three-dimensional schematic diagram of the insect source detection device of the Chilo suppressalis insect source detector according to an embodiment of the present invention.

[0017] Figure 5 Shown is a side view schematic diagram of an insect source detection device of a Chilo suppressalis insect source detector according to an embodiment of the present invention.

[0018] Figure 6 Shown is a cross-sectional schematic diagram of an insect source detection device of a Chilo suppressalis insect source detector according to an embodiment of the present invention.

[0019] Fig. 7A The figure shows a schematic diagram of the detection results of the insect source detection device of the Chilo suppressalis source detector according to an embodiment of the present invention, wherein the shadow outline shown in the figure is the Chilo suppressalis.

[0020] Figure 7B What is shown is a schematic diagram of the detection results of the insect source detection device of the Chilo suppressalis source detector according to an embodiment of the present invention, wherein the shadow outline shown in the figure is the Chilo suppressalis, and the edge of the shadow outline formed by the Chilo suppressalis forms a closed line.

[0021] Figure 8 Shown is a flow chart of a method for detecting a source of Chilo suppressalis according to an embodiment of the present invention. DETAILED DESCRIPTION

[0022] The following description is used to disclose the present invention so that those skilled in the art can implement the present invention. The preferred embodiments described below are only examples, and those skilled in the art can think of other obvious variations. The basic principles of the present invention defined in the following description can be applied to other embodiments, variations, improvements, equivalents, and other technical solutions that do not deviate from the spirit and scope of the present invention.

[0023] Those skilled in the art should understand that, in the disclosure of the present invention, the terms "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicating the orientation or position relationship are based on the orientation or position relationship shown in the drawings, which are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation. Therefore, the above terms should not be understood as limiting the present invention.

[0024] It is to be understood that the term "one" should be understood as "at least one" or "one or more", that is, in one embodiment, the number of an element may be one, while in another embodiment, the number of the element may be multiple, and the term "one" should not be understood as a limitation on the quantity.

[0025] Refer to the specification of the present invention Figure 1 , a striped stem borer source detector according to an embodiment of the present invention is illustrated, wherein the striped stem borer source detector of the present invention comprises a plurality of striped stem borer source detection devices 1, a housing 2 and a control panel 3, wherein the control panel 3 is arranged at an angle at the top of the housing 2 to facilitate a user to observe the control panel 3, and the plurality of striped stem borer source detection devices 1 are arranged in a space formed by the housing 2.

[0026] As shown in the attached picture Figures 2 to 6As shown, each of the striped stem borer source detection devices 1 of the striped stem borer source detector according to the embodiment of the present invention comprises an X-ray source array 10, a photosensitive plate 20 and a stage 30, wherein the photosensitive plate 20 is arranged to form a horizontal detection chamber 201, the X-ray source array 10 is horizontally arranged in the horizontal detection chamber 201, the stage 30 forms a detection space 301, and the stage 30 is arranged to keep the rice straw horizontally contained in the detection space 301, wherein the X-ray source array 10 is arranged to be driven to rotate around the detection space 301 formed by the stage, wherein the X-ray source array 10 is arranged to emit X-rays. Preferably, the photosensitive plate 20 is cylindrical, so that the horizontal detection chamber 201 is columnar. It can be understood that the photosensitive plate 20 of the Chilo suppressalis source detector according to the embodiment of the present invention is connected to the data processing module, and the data processing module is configured to image the rice stalks to be detected according to the data generated by the photosensitive plate 20 sensing X-rays, and detect and count the number of detected Chilo suppressalis according to the imaging.

[0027] It is worth noting that the stage 30 of the striped stem borer source detection device 1 of the striped stem borer source detector of the present invention can keep the rice straw horizontally contained in the detection space 301, and the X-ray source array 10 is horizontally arranged and rotated around the rice straw to avoid placing the rice straw vertically during detection. The vertical placement of the rice straw is not conducive to accurately detecting the number of striped stem borers in the rice straw. When the rice straw is placed vertically, the striped stem borers in the rice straw are likely to pile up together and are difficult to count. In addition, the stage 30 of the striped stem borer source detection device 1 of the striped stem borer source detector of the present invention can keep the rice straw horizontally contained in the detection space 301, and the X-ray source array 10 is horizontally arranged and rotated around the rice straw, rather than fixing the X-ray source array 10 and rotating the stage 30, in order to prevent the stage 30 from continuously rotating, causing the striped stem borers in the rice straw to move, so that their positions are constantly changing, which is not conducive to accurate imaging and counting.

[0028] As shown in the attached picture Figures 2 to 6As shown, the striped stem borer source detection device 1 of the striped stem borer source detector according to the embodiment of the present invention further includes a vibrator 50, wherein the vibrator 50 is configured to vibrate the stage 30. The rice straw to be detected is horizontally fixed on the stage 30, and the striped stem borers piled together can be dispersed by vibrating the stage 30 by the vibrator 50. In addition, if the striped stem borers in the rice straw are alive, the vibration of the stage 30 can also stimulate the striped stem borers to crawl, thereby making it possible to detect whether the striped stem borers in the rice straw are dead or alive, and what the proportion of the live striped stem borers to the total striped stem borers is by X-ray imaging technology. Therefore, the striped stem borer source detection device 1 of the striped stem borer source detector of the present invention can not only accurately detect the number of striped stem borers in rice straw by non-contact detection, but also detect the number of live striped stem borers in rice straw and the proportion of live striped stem borers to the total striped stem borers, thereby significantly improving the detection efficiency of the number of striped stem borer sources by plant protection agencies and the killing effect of pesticides on striped stem borers.

[0029] As shown in the attached picture Figures 2 to 6 As shown, the loading platform 30 of each of the striped stem borer source detection devices 1 of the striped stem borer source detector according to the embodiment of the present invention comprises a first loading base 31, a second loading base 32 and a plurality of connecting rods 33, wherein the plurality of connecting rods 32 are respectively horizontally arranged on the first loading base 31 and the second loading base 32, so that the detection space 301 is formed between the first loading base 31 and the second loading base 32. It can be understood that the first loading base 31 and the second loading base 32 can horizontally hold the rice straw to be detected therebetween.

[0030] As shown in the attached picture Figures 2 to 6 As shown, the first loading base 31 of the loading platform 30 of the striped stem borer source detection device 1 of the striped stem borer source detector according to the embodiment of the present invention forms a first fixing hole 310, and the second loading base 32 forms a second fixing hole 320. Further, the first fixing hole 310 of the first loading base 31 and the second fixing hole 320 of the second loading base 32 are configured to be inserted into both ends of the rice straw to be detected, so that the rice straw to be detected is horizontally held therebetween.

[0031] As shown in the attached picture Figures 2 to 6As shown, the X-ray source array 10 of the striped stem borer source detection device 1 of the striped stem borer source detector according to the embodiment of the present invention includes a rotating table 11, a plurality of X-ray sources 12 and a porous tube 13, wherein the porous tube 13 forms a fixed end 131 and a free end 132, wherein the fixed end 131 of the porous tube 13 is fixedly arranged at the outer edge 111 of the rotating table 11, the porous tube 13 forms a plurality of emission holes 130, the plurality of X-ray sources 12 are arranged in the porous tube 13, and the plurality of X-ray sources 12 are arranged to face the plurality of emission holes 130 of the porous tube 13 respectively, wherein the rotating table 11 is arranged around the first loading base 31 of the loading table 30, the plurality of emission holes 130 of the porous tube 13 are arranged between the fixed end 131 and the free end 132 of the porous tube 13 at intervals, and the porous tube 13 is placed horizontally. Accordingly, the porous tube 13 is located outside the stage 30, and when the rotating table 11 rotates, the porous tube 13 rotates with the rotating table 11, so that the porous tube 13 rotates around the detection space 301 formed by the stage 30. It can be understood that the multiple emission holes 130 of the porous tube 13 are arranged to face the detection space 301 formed by the stage 30, so that the X-rays emitted by the multiple X-ray sources 12 can be emitted to the rice straw to be detected which is horizontally arranged in the detection space 301. Preferably, after the vibrator 50 completes the vibration, the X-rays can be emitted to the rice straw to be detected by the multiple X-ray sources arranged in the horizontal direction of the X-ray source array. After the multiple X-ray sources arranged in the horizontal direction of the X-ray source array are controlled to emit X-rays to the rice straw to be detected at least once at a position or angle, the porous tube 13 is rotated around the detection space 301 formed by the stage 30 by a preset angle, and the multiple X-ray sources arranged in the horizontal direction of the X-ray source array emit X-rays to the rice straw to be detected again at least once at a new position or angle. In order to ensure that there is a difference between the images formed by the X-rays emitted by the multiple X-ray sources arranged in the horizontal direction of the X-ray source array at different positions, and the angle between the X-rays emitted by the multiple X-ray sources arranged in the horizontal direction of the X-ray source array at any two adjacent different positions should be not less than 30 degrees, but the angle between the two different positions should be avoided as much as possible. 180 degrees. It can be understood that the rice straw imaging can be obtained by processing the data generated by the photosensitive plate sensing X-rays by the data processing module. The image formed by the X-rays shows that there is a grayscale contrast between the images formed by the parts of the rice straw where the striped stem borer exists and the parts where the striped stem borer does not exist. The present invention uses the streaking method to count the striped stem borers.Exemplarily, first, the rice stalk to be detected is imaged according to the data generated by the photosensitive plate sensing the X-rays, and then, a line is drawn along the contour edge along the grayscale high area contour in the imaging, and the closed curve obtained by the line drawing is counted, so as to obtain the number of the striped stem borer. When the image formed by the X-rays emitted by the multiple X-ray sources arranged in the horizontal direction at different positions of the different X-ray source arrays is drawn and counted, the count with the larger number in the technical result shall prevail. The main reason is that when the striped stem borers are piled up in a ball in the rice stalks, due to the occlusion between the insects, there are differences in the number of closed curves in the graph formed by the X-rays at different positions. Therefore, when finally determining the number of the striped stem borers detected, it is also necessary to compare the number of the striped stem borers in the image formed by the X-rays emitted by the multiple X-ray sources arranged in the horizontal direction at different positions of the X-ray source array, and take the maximum number as the number of the striped stem borers finally detected.

[0032] As shown in the attached picture Figures 2 to 6 As shown, the rotating table 11 of the X-ray source array 10 of the striped stem borer source detection device 1 of the striped stem borer source detector according to the embodiment of the present invention has a receiving hole 1101, wherein the first loading base 31 of the loading platform 30 is rotatably received in the receiving hole 1101. Further, the vibrator 50 is disposed on a side of the first loading base 31 away from the second loading base 32 (or on the outer side of the first loading base 31).

[0033] As shown in the attached picture Figures 2 to 6 As shown, the X-ray source array 10 of the Chilo suppressalis source detection device 1 of the Chilo suppressalis source detector according to the embodiment of the present invention further includes a driving motor 14, and the rotating table 11 further includes a driving gear 112, wherein the driving gear 112 is fixedly arranged on the outer side surface 1110 of the outer edge 111 of the rotating table 11, and the output end 141 of the driving motor 14 is meshed with the driving gear 112, so that the driving motor 14 can drive the driving gear 112 to rotate through the output end 141, thereby driving the rotating table 11 to rotate and the porous tube 13 to rotate around the detection space 301 formed by the stage 30.

[0034] As shown in the attached picture Figures 2 to 6As shown, the Chilo suppressalis source detection device 1 of the Chilo suppressalis source detector according to an embodiment of the present invention further includes a baffle 40 and a handle 60, wherein the second loading base 32 of the loading platform 30 is fixedly arranged on the inner side of the baffle 40, and the handle 60 is fixedly arranged on the outer side of the baffle 40, so that the user can insert the rotating table 11 of the Chilo suppressalis source detection device 1 into the horizontal detection chamber 201 formed by the photosensitive plate 20 through the handle 60.

[0035] As shown in the attached picture Figures 2 to 6 As shown, the baffle 40 of the striped stem borer source detection device 1 of the striped stem borer source detector according to the embodiment of the present invention includes a baffle body 41 and an anti-radiation plate 42, wherein the anti-radiation plate 42 is arranged on the inner side of the baffle body 41. In other words, the second loading base 32 of the loading platform 30 is fixedly arranged on the anti-radiation plate 42 of the baffle 40. Preferably, the anti-radiation plate 42 is a lead plate.

[0036] According to an embodiment of the present invention, the present invention further provides a method for detecting a source of Chilo suppressalis, which comprises the following steps:

[0037] (a) placing the rice straw to be tested horizontally in a testing space, wherein the testing space is formed between a first loading base and a second loading base of a loading platform, and two ends of the rice straw to be tested are respectively fixed to the first loading base and the second loading base;

[0038] (b) vibrating the first loading base of the loading platform to cause the rice straw to be tested to vibrate, and the vibration duration is not less than 15 seconds;

[0039] (c) after the vibration is completed, emitting X-rays to the rice straw to be inspected through a plurality of X-ray sources arranged in a horizontal direction of the X-ray source array;

[0040] (d) receiving the X-rays passing through the rice straw to be detected through a photosensitive plate; and

[0041] (e) imaging the rice stalks to be inspected according to the data generated by the photosensitive plate sensing the X-rays, and counting the number of the detected rice stem borers according to the imaging.

[0042] It can be understood that the rice straw imaging can be obtained by processing the data generated by the photosensitive plate sensing the X-rays through a data processing module.

[0043] According to an embodiment of the present invention, step (c) of the method for detecting the source of Chilo suppressalis of the present invention comprises the following steps:

[0044] X-rays are emitted to the rice straw to be inspected at at least two different positions by a plurality of X-ray sources arranged in a horizontal direction of an X-ray source array, and the plurality of X-ray sources arranged in a horizontal direction of the X-ray source array emits X-rays at least once at each position.

[0045] According to an embodiment of the present invention, step (e) of the method for detecting the source of Chilo suppressalis of the present invention comprises the following steps:

[0046] Imaging the rice stalks to be inspected according to the data generated by the photosensitive plate sensing the X-rays; and

[0047] Draw a line along the edge of the grayscale high area in the image, and count the closed curves obtained by drawing.

[0048] According to an embodiment of the present invention, the method for detecting the source of Chilo suppressalis of the present invention further comprises the following steps:

[0049] (f) determining the closed curves formed by the detected striped stem borers according to the first imaging, numbering the closed curves formed by the detected striped stem borers, and recording the first detection positions of the closed curves formed by the striped stem borers with different numbers on the rice straw to be detected.

[0050] According to an embodiment of the present invention, the method for detecting the source of Chilo suppressalis of the present invention further comprises the following steps:

[0051] (g) after an interval of at least 1 minute, emitting X-rays to the rice straw to be inspected again at the same position through a plurality of X-ray sources arranged in a horizontal direction of the X-ray source array;

[0052] (h) receiving the X-rays re-emitted by the plurality of X-ray sources and passing through the rice straw to be detected through a photosensitive plate, and re-imaging;

[0053] (i) determining a closed curve formed by each detected Chilo suppressalis according to the re-imaging, and calculating the degree of agreement between the closed curve shape formed by each detected Chilo suppressalis in the re-imaging and the closed curve shape formed by each detected Chilo suppressalis in the first imaging, thereby determining the closed curve formed by each detected Chilo suppressalis in the re-imaging corresponding to the closed curve formed by the first imaging and the corresponding initial number, and recording the re-detected position of the Chilo suppressalis with the corresponding number on the rice straw to be detected; and

[0054] (j) comparing the first detection position and the second detection position of the rice stalk to be detected of the corresponding numbered rice stem borer, if the first detection position and the second detection position of the rice stalk to be detected of the corresponding numbered rice stem borer change, then the corresponding numbered rice stem borer is considered to be alive; and

[0055] If the numbered rice stem borer does not change between the first detection position and the second detection position of the rice straw to be detected, the numbered rice stem borer is considered dead, and the ratio of the number of live stem borers to the total number of detected rice stem borers is calculated.

[0056] It is worth noting that in order to reduce errors, when the degree of fit between the closed curve shapes formed by each Chilo suppressalis detected in the second imaging and the closed curve shapes formed by each Chilo suppressalis detected in the first imaging is calculated, the two closed curves with the highest degree of fit are closed curves formed by the same Chilo suppressalis at different positions.

[0057] For example, the closed curve shapes formed by each of the striped stem borers detected in the first imaging are X1, X2 and X3, and the closed curve shapes formed by each of the striped stem borers detected in the second imaging are x1, x2 and x3. If the degree of agreement between the closed curve shape x1 and the closed curve shape X1, the closed curve shape X2 and the closed curve shape X3 is 70%, 50% and 99%, then the closed curve shape x1 and the closed curve shape X3 correspond to the same striped stem borer, and the positions of the closed curve shape x1 and the closed curve shape X3 on the rice straw to be detected are compared. If the positions of the two do not change, then the striped stem borers corresponding to the closed curve shape x1 and the closed curve shape X3 are considered to be dead; if the positions of the two are different, then the striped stem borers corresponding to the closed curve shape x1 and the closed curve shape X3 are alive. The degree of agreement between two closed curves can be calculated using methods such as feature point matching method and ICP algorithm.

[0058] Those skilled in the art should understand that the embodiments of the present invention described above and shown in the accompanying drawings are only for illustrative purposes and are not intended to limit the present invention.

[0059] The purpose of the present invention has been completely and effectively achieved. The functional and structural principles of the present invention have been demonstrated and explained in the embodiments, and the embodiments of the present invention may be deformed or modified in any way without departing from the principles.

Claims

1. A device for detecting a source of Chilo suppressalis, characterized in that: include: An X-ray source array is configured to emit X-rays; Photographic plates; and The stage is provided with a photosensitive plate, wherein the photosensitive plate is arranged to form a horizontal detection chamber, the X-ray source array is arranged horizontally in the horizontal detection chamber, the stage forms a detection space, and the stage is arranged to keep the rice straw horizontally contained in the detection space, wherein the X-ray source array is arranged to be driven to rotate around the detection space formed by the stage.

2. The device for detecting the source of Chilo suppressalis according to claim 1, characterized in that: The stage includes a first carrier base, a second carrier base and a plurality of connecting rods, wherein the plurality of connecting rods are horizontally arranged on the first carrier base and the second carrier base, respectively, so that the detection space is formed between the first carrier base and the second carrier base.

3. The device for detecting the source of Chilo suppressalis according to claim 2, characterized in that: A vibrator is further included, wherein the vibrator is disposed on a side of the first carrier base away from the second carrier base, and the vibrator is configured to vibrate the carrier table.

4. The device for detecting the source of Chilo suppressalis according to claim 2, characterized in that: The X-ray source array includes a rotating table, a plurality of X-ray sources and a porous tube, wherein the porous tube forms a fixed end and a free end, wherein the fixed end of the porous tube is fixedly arranged on the outer edge of the rotating table, the porous tube forms a plurality of emission holes, the plurality of X-ray sources are arranged in the porous tube, and the plurality of X-ray sources are arranged to face the plurality of emission holes of the porous tube respectively, wherein the rotating table is arranged around the first loading base of the loading table, the plurality of emission holes of the porous tube are arranged between the fixed end and the free end of the porous tube at a distance from each other, and the porous tube is placed horizontally.

5. The device for detecting the source of Chilo suppressalis according to claim 4, characterized in that: The multiple emission holes of the porous tube are arranged to face the detection space formed by the stage, so that the X-rays emitted by the multiple X-ray sources can be directed to the rice straw to be detected which is horizontally arranged in the detection space.

6. The device for detecting the source of Chilo suppressalis according to claim 5, characterized in that: The rotating stage has a receiving hole, wherein the first carrier base of the carrier is rotatably received in the receiving hole.

7. The device for detecting the source of Chilo suppressalis according to claim 4, characterized in that: The X-ray source array further includes a driving motor, and the rotating table further includes a driving gear, wherein the driving gear is fixedly arranged on the outer side surface of the outer edge of the rotating table, and the output end of the driving motor is meshed with the driving gear, so that the driving motor can drive the driving gear to rotate through the output end, thereby driving the rotating table to rotate and causing the porous tube to rotate around the detection space formed by the stage.

8. The device for detecting the source of Chilo suppressalis according to claim 7, characterized in that: It further includes a baffle and a handle, wherein the second loading base of the loading platform is fixedly arranged on the inner side of the baffle, and the handle is fixedly arranged on the outer side of the baffle.

9. The device for detecting the source of Chilo suppressalis according to any one of claims 1 to 8, characterized in that: The photosensitive plate is in a cylindrical shape.

10. A Chilo suppressalis source detector, characterized in that: include: A plurality of devices for detecting sources of Chilo suppressalis according to any one of claims 1 to 9; a shell; and A control panel is provided, wherein the control panel is arranged at an angle on the top of the shell so that the user can observe the control panel, and the plurality of striped stem borer source detection devices are arranged in the space formed by the shell.

Images