The present invention relates to a flight mill. More specifically, the present invention relates to a flight mill with a self-twisted or twisted pair wire flight arm.

Flight mills are well-known devices used to measure the flight speed, range, and frequency of an insect. Early designs for flight mills are described in several publications, for example, Michel, R., Colin, Y., Rodriguez, M., and Richard, J. P. 1977, Automatic measurement and recording of insect flight activity., Entomologia Experimentalis et Applicata, 21, 199-206, Royley, W.A., Graham, C.L., and Williams R.E. 1967, Laboratory studies of mosquito flight I: A flight mill system, Technical Manuscripy 407, Defence Technical Information Center, and Chambers D.L., Sharp, J.L. and Ashley T.R. 1976, Tethered insect flight: A system for automated data processing of behavioural events., Behaviour Research Methods & Instrumentation, 8(4), 352-356.

Flight mills generally comprise a flight arm that is located perpendicular to a vertical axle and this flight arm is rotatable around the vertical axle. An insect is attached to the flight arm and, as the insect flies, the flight arm is rotated around the flight mill. A sensor is attached to the flight mill in order to monitor rotation of the flight arm.

The attachment of an insect to prior art flight mills has typically involved placing the insect in a cold environment or on a cold surface, such that the insect becomes quiescent. The insect is then prepared and glued onto the tip of the flight arm.

One of the disadvantages associated with the above-mentioned flight mills is that prior art flight arms have been comprised of a material which is not rigid enough to maintain its position during rotation, leading to "drooping" of the flight arm during rotation and inaccurate data being collected. In addition, insects of different sizes will require a flight arm of different lengths. For example, a mosquito will require a shorter flight arm than any of the common bee species. A lack of versatility in the length of the flight arm can lead to sub- optimal flight arms being used and the consequent introduction of inaccuracies and artefacts in the data collected.

Furthermore, if the material of the flight arm is too heavy, this can create drag, slowing the flight arm and exhausting the insect. Lighter flight arms can mitigate the problems associated with using heavier materials. However, in this case, the wires are typically thinner and can bend under the weight of the insect or over a period of time during an experiment. In addition, the variation in the weight of the flight arm would alter the circumference around which the insect has to fly and may therefore lead to inaccuracies in the data collected. Also, the prior art does not provide for a system whereby the insect is given a sufficient amount of time to return to a normal physiological condition following attachment to a flight mill. Attachment of the insect to the flight mill is often performed with glue having a high temperature which may cause stress to an insect and lead to inaccurate measurements of the insect's flight speed, frequency, and range.

The present application seeks to mitigate the above-mentioned shortcomings of prior art flight mill designs and methods of their use. In a first aspect, the present invention provides a flight mill comprising at least one twisted wire as the flight arm. When compared to conventional flight arms, twisted wire flight arms have the advantages of being light, flexible, have a high tensile strength, are durable, have low kinetic friction and are cost effective to manufacture. This allows for more accurate data to be obtained from a flight mill with twisted wire as the insect can fly in a state more closely comparable to that in nature. Where a single strand is used, the wire is rotated around itself to form what is termed a self-twisted wire. This type of wire provides the advantageous properties previously described. Two strands can be used to form the flight arm. For example, two finer wires can be rotated together to form what is termed a twisted pair wire. This type of wire provides the above-mentioned advantages but can be used to produce flight arms at a fraction of the weight of single strand self- twisted wires.

Preferably, the flight mill further comprises in use a vertical axle removably secured between two magnets. Typically, the vertical axle is secured to the upper magnet by magnetism. As the entire assembly, including the vertical axle and attached flight arm, can be removed, the insect attachment and detachment can be performed quickly and efficiently. The attachment and detachment of an insect can be a delicate procedure and it is beneficial to perform the attachment or detachment as efficiently as possible to reduce the handling time of the insect. Handling of the insects can lead to stress of the insect and/or accidental damage to the insect. Also, having a small contact area with the magnet reduces friction. In a conventional flight arm, as described above, the insect must overcome the friction generated by the flight arm turning around the vertical axle. In the present invention, the flight arm and vertical axle are secure by a small contact are to the upper magnet thereby reducing friction.

In one embodiment, the flight arm is secured directly to the vertical axle. Typically, the flight arm is secured to the vertical axle by welding. Having the flight arm attached to the vertical axle by welding provides a strong connection that cannot be broken by the force of the flight arm being rotated.

Preferably, the length of the flight arm correlates to the body mass of the insect to be attached to the flight arm. As the body mass of an insect increases, the optimum length of a flight arm also increases. This is a critical feature of a flight arm as the circumference in which an insect flies can alter the speed of the flight arm. In order to provide accurate data, a flight arm of an appropriate length should be used. As conventional flight arms often come in set lengths, sub-optimal flight arms are often used in experiments. However, a twisted wire flight arm of the exact optimal length for a given insect can be created quickly and cost effectively.

Preferably, the flight arm is formed from self-twisted wire and has a weight of 1 to 10 grams. In one embodiment, the self-twisted wire has a weight of 2 grams. In another embodiment, the self-twisted wire has a weight of 5 grams. The light weight of the self-twisted wires allows an insect to fly in a more natural manner as it does not have to pull a heavy conventional flight arm around the flight mill apparatus.

Alternatively, the flight arm is formed from twisted pair wire and has a weight of 0.1 to 0.6g. In one embodiment, the twisted pair wire has a weight of 0.2 grams. In another embodiment, the twisted pair wire has a weight of 0.5 grams. Twisted pair wires exhibit the same properties as self-twisted wire but are much lighter and, using twisted pair wire, very light weight flight arms can be made that can be used with very small insects such as mosquitoes.

Preferably, the flight mill includes a rotation sensor. Typically, the rotation sensor is a photosensor. A photosensor provides for an easy to use apparatus for the recordation of data from the rotation of the flight arm.

Preferably, the flight arm further comprises a detachable insect attachment means. Typically, the detachable insect attachment means comprises a pin for attachment to the insect, and a sleeve for securing the pin and insect to the flight arm. A detachable attachment means allows for an insect to be attached and data recorded and then detached such that the insect can rest prior to further attachment to the flight mill. Prior art flight arms have not provided for a means of attaching a pin to an insect, allowing the insect to rest so that it returns a physiological state more closely resembling that found in nature, attaching the insect to the flight arm, performing an experiment, then detaching the insect, and allowing it to rest. Therefore, using this apparatus, multiple experiments can be performed using the same insect. This would be greatly beneficial as, unlike prior art flight mills, experiments can be performed that measure the optimum resting time between flights of an insect.

In a preferred embodiment, the sleeve comprises rubber. Rubber has the necessary elastic properties that can be used to reversibly secure the pin to the flight arm. This provides a quick and efficient means for attaching the insect and is an easily replaceable part of the apparatus if it becomes damaged.

Preferably, the flight mill further comprises at least one controller module. Typically, the at least one controller module is a system on a chip microcontroller. In one embodiment, the at least one controller module is adapted to be connected to additional controller modules. Preferably, the or each controller modules operates using a synchronised clock. Using controller modules of the type described, allows for data from each flight mill to be recorded separately for each flight mill used but in combination the controller modules can be synchronised to record data from multiple flight mills using identical parameters.

Preferably, the flight mill further comprises an environmental simulator. In order to provide data that is as realistic as possible, various adaptations to the flight mill may be employed to recreate an insect's natural environment.

More preferably, the environmental simulator comprises a cylinder adapted to fit around the flight mill, the cylinder having black and white vertical stripes, may be used to provide a visual cue of actual movement. This adaptation to the flight mill is particularly important when studying bumblebees and honeybees. As the bees move around the flight mill the alternating white and black vertical lines provide a sensation of movement and travel rather than the completion of another loop around the flight mill. This helps provide more accurate data on the flight of an insect.

More preferably, the environmental simulator comprises a light source to simulate different light conditions. For example, the light source might be adapted to mimic dawn and dusk. The light source may be adapted to perform this function by having about 256 steps of light intensity and a range of light spectra from 411nm to 749nm. A preferable form of light source may be an LED light source. In a second aspect, the present invention provides a method for investigating flight characteristics of an insect using the flight mill as described above. The improved flight mill provides more accurate data due to the construction of the flight mill and allows for analysis of insects at more normal physiological condition. Preferably, the flight mill is used in conjunction with an environmental simulator. An environmental simulator increases the accuracy of the data collected and may allow for necessary stimuli to encourage insects to perform certain types of behaviour when attached to the flight mill. Preferably, the method above includes the step of assessing an appropriate length of flight arm, forming a flight arm by forming at least one twisted wire, and investigating the flight characteristics of an insect using a flight mill. As is known, it is important to use the correct length of flight arm for the insect used. The present invention allows for the creation quickly and cost efficiently of a flight arm of optimum length.

In a third aspect, the invention provides a method of manufacturing a flight mill with a flight arm comprising a self twisted or twisted pair wire The invention will now be described by way of example with reference to the accompanying drawings in which the same reference numerals are used to indicate the same or similar parts of the invention, wherein:

Figure la shows a side view of a prior art flight mill;

Figure lb shows a schematic diagram of the flight arm and vertical axle of a prior art conventional flight mill; Figure 2 shows a side view of a first embodiment of a flight mill according to the invention with a flight arm made from self-twisted wire; Figure 3 shows a perspective view of a part of the flight mill of Figure 2;

Figure 4 shows a graph of a tensile strength experiment using a self-twisted wire 0.5mm in diameter and an untwisted wire 0.5mm in diameter at 100mm, 150mm, 200mm, 250mm, and 30mm in length;

Figure 5 shows a side view of a part of the apparatus of Figure 2;

Figure 6 shows a side view of a second embodiment of a flight mill with a twisted pair wire flight arm;

Figure 7 shows a schematic diagram of multiple flight mills according to the invention linked to controller modules;

Figure 8 shows a block diagram of the flight mills electronics system; and

Figure 9 shows a flow chart of the operations performed by the controller.

Figure la shows a conventional prior art flight mill 100. A vertical axle 200 is fixed to the base of the flight mill 100 and runs through the centre of a fixed lower ring shaped magnet 400. The vertical axle 200 also runs through the centre of an upper ring shaped magnet 300 which is rotatable around the vertical axle 200. The opposing poles of the upper ring shaped magnet 300 and lower ring shaped magnet 400 are orientated to face one another. As the vertical axle 200 runs through the centre of magnets 300 and 400, it secures them and the opposing magnetic poles causes the upper magnet 300 to "float" above the lower ring shaped magnet 400. The flight arm 500 is secured to the surface of the upper ring shaped magnet 300 and, therefore, can rotate around the vertical axle 200 due to the "magnetic levitation" generated by magnets 300 and 400. A sensor disc 600 monitors the rotation of the flight arm 500 and can be used in conjunction with a photosensor. The flight arm 500 has a section for attaching an insect 700 at one end and a counter balance 800 at the other. Flight mills known in the art typically have a flight arm comprised of stainless steel hypodermic tubing. However, the flight arm may also be made of a plastic or rigid metal wire. As an insect flies it will pull the flight arm 500 around the vertical axle 200 and the characteristics of the flight of an insect can be measured using the sensor disc 600. The flight arm can be seen in more detail in Figure lb. As can be seen from Figure la and lb, the movable section of the flight arm is quite large and the insect would have to overcome the weight of this flight arm to begin its rotation. Additionally, during flight when attached to the flight mill, the insect would have to overcome the friction generated by the flight arm turning around the vertical axle.

Figure 2 shows a first embodiment of the flight mill 1 comprising a self-twisted wire flight arm 2. The self-twisted wire flight arm 2 is coupled to a vertical axle 3 and a detachable insect attachment means 4 is attached to one end of the self- twisted wire 2. The vertical axle 3 is coupled to the upper magnet 5 by magnetism. The magnetic field generated by the lower magnet 6 provides a stabilising force that retains the vertical axle 3 in position during rotation, while at the same time providing a means of near frictionless rotation. The upper magnet 5 and lower magnet 6 are fixed to upper magnet support 7 and lower magnet support 8. Supports 7 and 8 are positioned such that the magnets are provided at an optimal distance to exert the required magnetic field upon vertical axle 3. A rotation sensor 9 is attached to the lower magnet support 8. A sensor disk 10 is attached to the vertical axle 3 below the flight arm 2. As an insect turns the flight arm 2, the sensor disk 10 will rotate through the rotation sensor 9 and data, such as rotation speed and rotation time, collected for analysis.

Figure 3 shows the removable vertical axle 3 and attached flight arm 2. A detachable insect attachment means 4 is located at one end of the flight arm 2 and a sensor disk 10 is attached to the vertical axle 3 below the flight arm 2. Figure 3 shows the fine upper tip of the removable vertical axis 3 above the flight arm 2. This tip contacts upper magnet 5 and provides as little surface area in contact with the magnet as possible, which helps to reduce friction as the vertical axle 3 turns.

The self-twisted wire used to form the flight arm shown in Figures 2 and 3 is superior to prior art flight arms because it is light, flexible, has a high tensile strength, is durable, and has low kinetic friction. A conventional flight arm as used in the prior art typically weighs between 25 and 35 grams. This is in contrast to the present invention, wherein the flight arms are made using self-twisted wires which are approximately 5 grams in weight. However, the present invention may also use extremely lightweight flight arms which may be between 1 and 2 grams in weight.

The self-twisted wire and the pair twisted pair wire of the present invention can be manufactured by rotating a wire around itself or two fine wires around each other at high speed. This advantageously produces a stronger wire having a higher tensile strength, whilst keeping the weight of the twisted wire to a minimum.

This method of producing wires ideally suited for use as flight arms is also an extremely cost-effective and can be done at a fraction of the cost of using other suitable materials. The preferred material of the wires in the present invention is galvanised steel. Galvanised steel wires of 0.2mm, 0.5mm, 0.7mm and 1.5mm in are preferably used to produce the self-twisted and twisted pair wires.

The procedures to produce twisted wire and twisted pair wires are as follow:

Example 1 i. Cut the galvanised wire into workable length, preferably within 1.2 to 1.5 meter. ii. Secure one end of the wire using vice and insert the other wire's end into a hand drill. iii. Create tension between the vice and the hand drill to make the galvanised wire into a straight line. iv. Switch ON the hand drill at a manageable speed, approximately 600rpm until the galvanised wire snap at the hand drill's tip. v. Cut the twisted wire to usable/desirable length for flight mill construction.

Example 2 i. Cut 0.2mm wires into a workable length, preferably about 20cm. ii. Selects two wires with the same length and twist both end of the wire together by hand. iii. Secure one end of the twisted pair wire using vice and insert the other wire's end into a hand drill. iv. Create tension between the vice and the hand drill to make the twisted pair wire into a straight line. v. Switch ON the hand drill with a very slow speed, approximately 60rpm until the twisted wire forms 5 twists within 1cm. vi. Cut the twisted pair wire to usable/desirable length for flight mill

construction. To demonstrate the improved properties of the self-twisted wire of the present invention, compared to an untwisted wire of the same diameter, a tensile strength analysis was performed. Figure 4 shows the results of this test and demonstrates that a 0.5mm self-twisted wire has a far higher tensile strength than an 0.5mm untwisted wire (the untwisted wire comprising the same material as the material used to create the self-twisted wire). Both the twisted and untwisted wires were tested at 100mm, 150mm, 200mm, 250mm, and 300mm in length and five replicates were performed for each length of wire. To perform the test, the wires were clamped in a vice and a lOg load was applied to the free end of the wires for a period of three seconds. The deflection from the original position was measured. The results clearly illustrate the great improvement of the tensile strength of the twisted pair wire when compared with the untwisted wire. The 10 g load deflected the self-twisted wire far less than the untwisted wire. The deflection of the untwisted wire becoming more pronounced as the length of the wire tested increases.

Table 1 shows the results of a test of the kinetic friction of a self-twisted pair wire flight arm in comparison with that of a conventional flight arm. The dimensions of a convention flight arm can be seen in Figure lb. The conventional flight arm used in this experiment was identical to those presently used by the Washington State University. As previously described above, the convention flight arm used is formed from stainless steel hypodermic tubing and is attached to a ring-shaped magnet. The ring shaped magnet slots through a vertical axle positioned at the centre of the ring shaped magnet and the magnet is positioned above a second magnet that has an opposing pole facing the first magnet.

The kinetic friction was measured using the standard Galileo's ramp and a 3.5g metal sphere was used to generate the controlled force. The sphere was allowed to roll down the gradient of the ramp and into the flight arm of a self twisted wire flight arm and a conventional flight arm. The distance the flight arm moves after application of the force of the metal sphere demonstrates the kinetic friction properties of the flight arm.

Table 1

Self-twisted wire Conventional

flight arm flight arm

mean 0.0917 0.1212

standard deviation 0.0257 0.0337

standard error 0.0105 0.0137

The above results illustrate that the twisted wire flight arm has greatly reduced kinetic friction when compared to an untwisted prior art flight arm.

Figure 5 shows the components of an embodiment of the detachable insect attachment means 4. The pin 4a can be glued onto the back of an insect. Following attachment to pin 4a, the insect is allowed a period of time to recover from the procedure and return to a physiological state which is closer to that found in nature. In contrast, prior art flight mills often attach the insect directly to the flight arm and begin flight tests immediately after attachment. This may produce inaccurate results as the insect is reacting to the stress of the attachment procedure.

Following attachment to pin 4a and a return of the insect to a more natural physiological state, the pin 4a can be attached to the flight arm by inserting pin 4a into sleeve 4b. Sleeve 4b is in turn attached to hook 4c provided at its other termini. Hook 4c creates the connection to the flight arm. The sleeve 4b could be formed from many materials, however, rubber would be a preferable choice due to its elastic properties. After an experiment has been completed, pin 4a can be removed from sleeve 4b and the insect may be returned to its enclosure. If so desired, the experiment can be repeated using the same insect. Therefore, a single insect can be used in multiple experiments.

Figure 6 shows a second embodiment of the flight mill 1. In this embodiment, two parallel twisted pair wires 2 are secured together. One wire has been bent at both ends to form two vertical stems substantial along the axis of the vertical axle 3. A second twisted pair wire is secured to the first providing added support and strength to the structure. In this embodiment, the other elements of the flight mill are the same as those described in the first embodiment, i.e. the rotation sensor 9, rotation sensor disk 10, lower magnet 6, and lower magnet support 8.

Figure 7 shows a schematic diagram of multiple flight mills which are linked to a controller. The multiple flight mills can be linked to multiple controller modules and the amount of controller modules can be varied depending upon the number of flight mills in operation.

Figure 8 shows a block diagram of the flight mills electronics system and the system on a chip approach to flight mill controllers as shown in the present invention.

Figure 9 shows a flow chart showing the operations of the controller. The controller can store and process data and upon command transfer this data to a computer for analysis.