The Lamp Still Looks Fine: Ultraviolet Decay, Placement Errors, and Reading an Insect Light Trap as Data

1. Introduction: the instrument nobody reads

Every food premises has them. They are serviced, the boards are changed, the catch goes in the bin, and a line appears on a report saying the units were checked.

Almost none of that treats the device as what it is, which is a monitoring instrument with a sensitivity that declines invisibly and a placement that determines what it measures.

1.1 Why this article follows the last one

The previous article found that audits examine documentation rather than outcome. This is the device that generates most of the documentation, and its output can be entirely compliant while the instrument behind it has quietly stopped working.

2. What the lamp actually is

A detail that explains the whole decay problem.

Fluorescent tubes produce light through a reaction involving gases and mercury vapor interacting to produce ultraviolet light. For general lighting the inside of the tube is coated with a phosphor coating which emits a white fluorescent light. That coating is either less densely applied or eliminated altogether in the ultraviolet fluorescent tubes used in flying insect traps.⁴

2.1 The wavelengths involved

Experimental work on diode traps tested combinations at 365, 385 and 405 nanometres at constant total power.⁶ The lower end of that range is well outside human vision and the upper end is at its violet edge.

Which is why a unit looks dim and blue while doing most of its work in a band nobody in the room can perceive.

2.2 What that means

An ordinary fluorescent tube makes ultraviolet and converts it to visible light. A trap lamp is the same device with the conversion layer removed or thinned, so the ultraviolet escapes.

The blue glow people associate with these units is incidental. The working output is the part nobody can see, which is §4.

3. The decay problem

The measured decline.

Over a period of about twelve months, light output from a fluorescent tube may reduce by 25 per cent or more. The output reduces significantly over time, which reduces the attractive power of the attraction section over time.²

3.1 A quarter in a year

That is not a marginal decline. A unit two years into service on its original lamp may be operating at roughly half its original attractant output, if the decline continues at a similar rate.

The extrapolation is ours; the source reports a figure at twelve months and does not give a curve.²

4. Why the failure is invisible

The property that makes this different from ordinary equipment degradation.

The wavelength doing the attracting is outside human vision. A technician looking at a unit sees whether it is lit, which is a different question from whether it is working.

4.1 The comparison this journal keeps making

A rodent station with a spent bait block looks the same as one with a fresh one from a distance. A monitor left too long saturates without announcing it. A detection dog's accuracy drifts with no signal to the handler.

In each case the instrument degrades and the record does not change, which is the general failure this journal has now documented across four monitoring technologies.

5. What that does to the record

The consequence that should worry anybody reading a trend report.

Catch falls as output falls. A declining catch is the pattern everyone wants to see, and it is produced both by successful control and by a failing lamp.

5.1 The two readings are indistinguishable on the data

Nothing in a monthly count separates fewer insects present from fewer insects attracted. Both produce the same graph pointing the same direction.

That is the confounding this journal described for pheromone trap catches, where the number was a joint product of population and trap attractiveness. Here the attractiveness declines on a schedule nobody records.

5.2 The one thing that would separate them

A lamp change. If catch rises sharply after a new lamp goes in, the decline before it was the instrument rather than the population.

That makes the annual replacement in §6 a measurement as well as a maintenance task, provided somebody records the catch either side of it. Nobody we are aware of does, and it would cost nothing.

5.3 Why this favours the wrong conclusion

A rising catch prompts investigation. A falling catch prompts nothing, because it reads as success.

So the failure mode of this instrument produces exactly the signal least likely to be questioned, and that observation is ours.

6. The replacement rule

What guidance recommends, and its reasoning.

Change UV lamps at least annually, before spring, because output falls off long before the lamp dies. Replacement should be timed for early spring, before the fly season.¹

6.1 A rule rather than a measurement

Notice the form of the guidance. It does not say to test output and replace when it falls below a threshold; it says replace annually regardless.

That is the correct design for a failure nobody can observe. Where degradation is invisible and measurement is impractical, a calendar is the only instrument available, which is the same reasoning this journal applied to the second flea treatment and the second lice application.

6.2 The two parts of that instruction

Annually, which addresses the decay. And before the season, which addresses when the instrument most needs to be working.

Replacing lamps in autumn satisfies the first and wastes most of the benefit, since the unit spends its best months in the period with fewest flies.

6.3 The Manitoba timing

The guidance quoted is written for a southern hemisphere season. Translated to this province the equivalent is replacement in late winter or early spring, before the seasonal fly population develops.

That is our adaptation of the principle rather than a sourced local recommendation.

7. The diode comparison

The alternative lamp technology and what it changes.

Light emitting diodes are described as advantageous because there is no fade in light output over time compared to fluorescent tubes, with the comparison showing that over twelve months a fluorescent tube may lose a quarter or more of its output while no reduction is experienced with diodes.²

7.1 What that would change operationally

If output does not decline, the annual replacement in §6 is addressing a problem that no longer exists, and the unit's sensitivity stops being a hidden variable.

That is a larger benefit than energy consumption or lamp life, because it removes the confounding in §5 rather than reducing a cost.

7.2 The source and its interest

This comparison comes from a patent specification for a diode-based trap, which is a document written to establish the advantages of the invention.² We would treat the direction as well established and the specific figures as the applicant's.

8. The geometry problem

Why diodes are not simply a drop-in replacement.

Fluorescent tubes sit in front of the glueboard, ensuring as much of the glueboard as possible is useful for catching flies. If diodes are used, due to their wiring requirements, they cannot sit in front of the glueboard, because the typical point source of an LED cannot replicate the 360 degree illumination of a fluorescent tube, so they are positioned around a perimeter of the glueboard instead.²

8.1 The consequence of even illumination

Evenly spread diodes provide an even spread of ultraviolet light, so that the glueboard then has a longer life, because the space on the glueboard is used more evenly and there is a reduced likelihood of sections becoming overloaded with trapped pests.²

That is a second-order benefit worth noticing: a board that fills evenly reaches saturation later than one that fills in a hot spot, which affects §17.

9. Distance from lamp to board

A design constraint that also governs whether a unit works.

Effective traps position the light sources as close as possible to the immobilisation section, especially the glueboard, because if parts of the glueboard are too far away from the light sources, they will not catch insects, or the effectiveness will be substantially reduced.²

And if the light source is any distance from the glue board, insects attracted to the light source may never meet the glue board and, thus, may fly away without being captured.⁷

9.1 Why this constrains everything else

The lamp has to be close to the board, and the board has to be behind or below the lamp, and the opening has to face the room. Those requirements largely determine what a unit can look like, which is why so many of them look alike.

It also explains why the design literature is full of patents: the geometry is genuinely constrained, and the improvements available are small rearrangements of the same three components.⁷

9.2 Attraction and capture are separate problems

Bringing an insect to a unit is not catching it. A trap that draws flies to a bright opening and then lets them leave has increased fly traffic in that part of the room without capturing anything.

Experimental work found that placing lights within a few inches of the boards and directing them at the boards produced a concentration of flies in the most intensely lit area and an improved catch.⁶

10. Why shape matters

A design factor with an interesting proposed explanation.

A unit that is wide is considered more effective at catching flies than ones that are circular or tall and narrow, because of the shape and orientation of the lamps in the unit and the shape of the light emitted. When lamps are orientated horizontally, wide, discrete bands of light are emitted that flies are attracted towards, and it is thought this is because it mimics natural shapes of light, such as a horizon.³

10.1 The status of that explanation

Offered as a thought rather than a finding, by a commercial source.³ We record it because the horizon hypothesis is plausible and testable, and because the practical observation about wide units stands independently of whether the explanation is right.

11. The commonest placement error

The conceptual mistake that determines whether a unit helps or harms.

The single most common placement error is treating the trap as an attractant to hang in the middle of the room. A well-placed unit intercepts insects on the routes they already take, mainly as they come in through doors.¹

11.1 Why the error is so natural

The device is marketed as an attractant and works by attraction, so hanging it centrally where it can reach the whole room is the obvious inference. It also looks like coverage on a site map.

The inference fails because attraction is not the objective. Catching an insect after it has crossed a production area has already allowed everything you were trying to prevent.

11.2 The distinction being drawn

An attractant pulls insects toward itself from wherever they are. An interception sits on a path insects are already using and catches them in transit.

A unit in the middle of a production room is being asked to pull flies across the room, through the space you least want them in, in order to catch them.

12. The dusk test

The best free diagnostic we have encountered in this trade.

Stand outside each external door at dusk. If you can see the blue glow of an insect light trap from the yard, that unit is drawing insects in. Move it out of the sightline.¹

12.1 Why dusk specifically

Because the comparison in §13.1 is with ambient light. In daylight the unit is invisible against the sky and in full darkness everything glows; at dusk the interior light is brighter than outside and the sightline is visible.

It is also when many flying insects are most active and orienting to light, so the test is performed under the conditions it is meant to predict.

12.2 Why it works

Light travels in both directions. A unit that can be seen from outside is visible to everything outside, and a device designed to attract flying insects is doing so across the threshold.

The test converts an invisible design question into a thing a person can check in two minutes without equipment.

12.3 The failure mode it catches

A unit placed correctly for interception, on the inside of a door, positioned so the doorway frames it. That is a near miss rather than an obvious error, and it turns a control device into a recruitment device.

12.4 Why we like this test

Because it requires nothing, can be done by the client, and produces an unambiguous answer. Most of what this journal recommends requires expertise or equipment; this requires standing in a car park at the right time of day.

13. Competing light

A placement factor that is easy to assess and often ignored.

Bright windows, skylights and other lit fixtures compete with the trap. A unit fighting daylight from a rooflight catches a fraction of what it should.¹

13.1 What competing means physically

An insect orienting to light is choosing among sources. A unit is not attractive in absolute terms; it is attractive relative to everything else visible from where the insect is.

That reframes placement as a question about the whole lighting environment rather than about the unit, and it is why §12 and §13 are the same problem seen from inside and outside.

13.2 The implication for daytime

Under a rooflight in daylight the unit is a minor source competing with the sky. Whatever it catches, it is catching in spite of its position, and its useful hours are the ones after the light outside has gone.

In a premises operating a day shift only, that may mean the unit does most of its work when nobody is present and the doors are shut, which is the opposite of the interception role §11 describes.

Combined with §3, a unit under a skylight on a two-year-old lamp is operating at a small fraction of its potential on both counts simultaneously, and its declining catch will read as success.

14. Clearance from product

The safety rule, which is also why unit type matters in §15.

Never mount a unit directly above or facing open lines, filling heads, exposed product or open packaging. A shattering lamp or a dislodged insect fragment over product is a contamination event. Units should be kept at least 1.5 to 2 metres clear of exposed product zones.¹

14.1 Why this rule constrains placement more than it appears

Combined with §11, a unit must be near a door, away from competing light, out of sightline from outside, and one and a half to two metres clear of any open product.

In a small or congested premises those four conditions may have no intersection, at which point the honest answer is that the unit does not go there and the fly problem is addressed by the door rather than the device. That conclusion is ours.

14.2 Two different hazards in one rule

Glass, from a lamp failure. And insect material, from the catch itself.

The second is the one people forget. A trap full of flies mounted over a line is a reservoir of foreign material held directly above the product, and its contents are what the device exists to accumulate.

15. Grids against glue boards

The choice that follows from §14.1.

Units used in food-handling businesses should have a glueboard or roll rather than an electric grid, so that flies are contained hygienically in the units and insect fragments aren't scattered around the area by an electric shock.³

Wall-mounted encapsulating glue board units are preferred in production because they contain the insect and the fragments.¹

15.1 Why grids persisted anyway

They need no consumable. A glue board is bought, changed and disposed of every month, and a grid is not, which makes the grid cheaper to run and easier to neglect.

That is the same economics this journal found behind monitoring generally: the option with the recurring cost is the one that works, and the one with no recurring cost is the one that gets installed and forgotten.

15.2 What an electrocuting grid does to an insect

It kills it with a discharge, and the insect is not neatly retained. Fragments are projected from the unit, which in a food production environment is a dispersal mechanism rather than a control one.

Historic designs used an exposed bulb with high voltage electrocuting systems,⁸ and some intermediate designs used a low voltage pulse that causes the insect to fly down onto a nontoxic adhesive trapping board,⁸ which is a hybrid addressing the same problem.

15.3 The wider consequence

An insect carries whatever it landed on last, which for a filth fly may be material this journal's drain and small fly articles described. Distributing it as fragments through a production area is worse than the fly being there.

16. Monitoring units against control units

A distinction guidance says should be made first and usually is not.

The first thing to consider is the difference between units that monitor or control a population, because monitoring units and control units look similar, but perform different tasks on premises and areas within premises with varying risks. Monitoring traps are usually glueboard units that allow a technician or field biologist to count the catch.³

16.1 Why the distinction matters

A control unit is placed to reduce a population. A monitoring unit is placed to measure one, which means it should be positioned where the measurement is informative rather than where the catch is highest.

Those two objectives point at different locations, and a programme that does not distinguish them has units doing neither job well. This journal made the same argument about surveillance against delimitation in the detection article.

16.2 Where each type belongs

A control unit belongs where flies concentrate, which is usually near the door they came through or the waste they are using. A monitoring unit belongs where a change in catch would tell you something, which may be a low-traffic area whose numbers should be near zero.

A programme of identical units spaced evenly through a building is treating placement as coverage, which is the same error §11 describes applied at the scale of the whole site. That framing is ours.

16.3 What the units are checking

Guidance frames the monitoring function as verifying that your exclusion equipment and policies, door, fly-screens, door-policy education, are working as they should.³

So the instrument is not primarily measuring flies. It is measuring the building envelope and the behaviour of the people using it, which is the argument this journal has made about exclusion from the first article onward.

17. The glue board schedule

The second consumable and its rule.

Change glueboards on a defined schedule, typically monthly, more often in peak, and never let a board saturate.¹

17.1 Why a schedule rather than an inspection

Same reasoning as §6.1. Judging whether a board is near saturation by looking at it is a judgement call made by somebody with an incentive to defer the change, and a defined interval removes the judgement.

17.2 Why saturation matters for the data

A saturated board stops catching. Its count for that period is a floor rather than a measurement, and it is indistinguishable in a spreadsheet from a real number.

It is also the case where §8.1's even illumination helps, because a board that fills uniformly reaches that ceiling later than one filling in a bright spot.

18. Reading the catch

The use almost nobody makes of what is already being collected.

Identify and trend the catch by species: houseflies, fruit flies and stored-product moths each point to a different failure.¹

18.1 Three different buildings

House flies point outward, at doors, waste storage and external breeding. Small flies point inward and downward, at drains and organic accumulation, which this journal's drain biofilm article dealt with at length. Stored product moths point at a commodity, which means something in the building is infested.

The same count of the same number of insects means three entirely different things depending on what they are. Forty house flies is a door problem. Forty small flies is a drain problem. Forty moths means somebody should open a bag.

18.2 The identification does not need to be to species

Separating a house fly from a small fly from a moth is a coarse distinction any technician can make on a board without magnification, and it is enough to point at three different remedies.

That is worth stating because this journal's article on automated identification concluded that species-level machine identification is not yet reliable for confusable sets. Group-level sorting does not need it, and group level is where most of the diagnostic value sits.

18.3 Why this is the highest value step available

The catch is already there. It has already been collected, paid for and thrown away. Identifying it converts a disposal task into the only continuous species-level surveillance data a food premises generates.

The previous article in this journal argued that our reports record outcomes without effort. Here is a case where the data exists and is discarded, and that is our characterisation.

19. Mapping the units

The documentation point, stated well in the guidance.

Every unit is numbered and marked on the pest control site map in its true position, exactly as the rodent stations are, so the map reconciles to the floor in both directions.¹

19.1 Why the lamp date belongs on the unit

Section 21 recommends it and the reasoning is §4. The only way an invisible failure becomes visible is a written date somebody can read off the housing.

A change logged in an office system is a record. A date on the unit is a check anybody standing in front of it can perform, including the client and the auditor, which converts a private record into something verifiable in the building.

19.2 Reconciling in both directions

Every unit on the map exists on the floor, and every unit on the floor appears on the map. Those are different checks and only doing both catches a unit that was moved, removed or added.

It is also precisely what an auditor can verify in the time available, which the previous article identified as the constraint on what audits examine.

20. The illumination finding

A research result that complicates the assumption that constant operation is optimal.

Researchers assigned pairs of electrocutor-grid ultraviolet light traps to treatments to evaluate the effects of illumination events, for example light traps turned on, on house fly attraction as indicated by numbers of flies captured. One treatment had both traps illuminated constantly, with no illumination event. Another had both traps turned on, illuminated for 1 hour, then turned off for 1 hour, then repeated, giving one illumination event every two hours. The reported conclusion is that turning the traps on and off increases their attraction to house flies.⁵

20.1 What the design isolates

Pairs of traps in the same setting, differing only in whether they were cycled.⁵ Holding location and period constant and varying one factor is what makes a field result about attraction interpretable at all.

20.2 Why this is interesting

It suggests the change in illumination is itself attractive, rather than the steady state, which is not how anybody operates these units.

20.3 What we would not do with it

Recommend cycling units in a food premises. A trap switched off for half of every period is not catching for half the time, and the study measures attraction rather than total capture over a period.

We record it as a finding about fly behaviour rather than an operating instruction, and the authors themselves note that most evaluations are conducted only under laboratory conditions and that fly behavior in relation to the traps has not been fully described in the literature.⁵

21. What we would do

Replace lamps annually before the season. Output falls off long before the lamp dies.¹

Do the dusk test at every external door. Free, fast and unambiguous.¹

Move units off the middle of rooms. Intercept rather than attract.¹

Glue board, not grid, in food areas. Contain the fragments rather than scattering them.³

Keep well clear of open product. One and a half to two metres.¹

Identify the catch to group. Three groups, three different problems.¹

Record the lamp change date on the unit. Nothing else makes the decay visible.

22. Limitations and open questions

Much of this comes from patents and trade guidance. Five of the eight sources are patent specifications written to establish the merits of an invention, and two are pest control company guidance with a commercial interest.¹²³⁶⁷⁸

The decay figure is from an interested party. Stated in §7.2. We located no independent measurement of ultraviolet output decline against catch in a working facility.²

No efficacy data at all. We found no study measuring how much a correctly placed and maintained programme reduces fly presence compared to an incorrectly placed one, which is the question a facility would most want answered.

The illumination study used electrocutor grids. Which §15 says are the wrong unit for food handling, so its applicability to glue board units is unestablished.⁵

The guidance is written for other jurisdictions. The placement source is South African and the season is inverted, addressed in §6.2. Manitoba fly seasonality, and the much longer period during which external doors are kept shut, may change the weighting of several recommendations.¹

Sections 3.1, 4.1, 5, 9.1, 12.3, 15.2, 16.1, 18.2 and 19.1 are our reasoning. The two-year extrapolation, the comparison with other degrading instruments, the confounding argument, the attraction against capture distinction, the assessment of the dusk test, the fragment dispersal point, the monitoring against control argument and the discarded data observation are ours rather than sourced positions.

Our commercial position. Annual lamp replacement and more frequent board changes are consumables a pest control company sells. We have tried to offset that by noting that the dusk test, the placement corrections and identifying the catch cost nothing and are mostly things a client can do or check themselves.

23. Conclusion

The attractant in an insect light trap is invisible, and fluorescent output can fall a quarter or more in a year while the tube keeps lighting normally.¹² So the instrument loses sensitivity on a schedule nobody observes, and because a declining catch reads as successful control, the failure produces the one signal nobody investigates.

Placement decides the rest. The commonest error is hanging the unit in the middle of a room as an attractant rather than placing it on the route insects already take, and a unit visible from the yard at dusk is recruiting rather than intercepting.¹ In a food area the catch should be held on a board rather than thrown off a grid, because the insects in the unit carry whatever they last landed on.³

What stays with us is §18. The catch is collected every month, at cost, in every food premises in the country, and then binned. Identifying it to group takes minutes and tells you whether your problem is the doors, the drains or the stock, which is the difference between three entirely different remedies. The most valuable surveillance data in the building is already being paid for and thrown away.

References

1. Insect Light Trap Placement in Food Facilities. Commercial pest control company guidance. Trade source with a commercial interest, cited as attributed material. Used for the instructions to change ultraviolet lamps at least annually and before spring because output falls off long before the lamp dies; for the statement that ultraviolet output is invisible to the eye and decays steadily, so a lamp that still looks bright can be emitting a fraction of the attractant wavelength it did when new and a working lamp is not necessarily an effective one; for the instruction to change glue boards on a defined schedule, typically monthly and more often in peak, and never let a board saturate; for the instruction to identify and trend the catch by species, with house flies, fruit flies and stored-product moths each pointing to a different failure; for the statement that the single most common placement error is treating the trap as an attractant to hang in the middle of the room whereas a well-placed unit intercepts insects on the routes they already take, mainly as they come in through doors; for the rule never to mount a unit directly above or facing open lines, filling heads, exposed product or open packaging because a shattering lamp or dislodged insect fragment over product is a contamination event, with units kept at least 1.5 to 2 metres clear of exposed product zones; for the statement that wall-mounted encapsulating glue board units are preferred in production because they contain the insect and the fragments; for the warning that bright windows, skylights and other lit fixtures compete with the trap so that a unit fighting daylight from a rooflight catches a fraction of what it should; for the instruction that every unit is numbered and marked on the pest control site map in its true position, exactly as rodent stations are, so the map reconciles to the floor in both directions; and for the dusk test, that standing outside each external door at dusk and seeing the blue glow of a unit from the yard indicates that unit is drawing insects in and should be moved out of the sightline. https://ascpestcontrol.co.za/blog/insect-light-trap-placement-food-industry
2. Pest trap. United States patent specification. Written to establish the merits of a diode based design, cited as attributed material. Used for the statements that effective pest traps position the light sources as close as possible to the immobilisation section, especially the glue board, and that if parts of the glue board are too far from the light sources they will not catch insects or effectiveness will be substantially reduced; that fluorescent tubes sit in front of the glue board ensuring as much of it as possible is useful, whereas light emitting diodes cannot sit in front of the glue board because the typical point source of a diode cannot replicate the 360 degree illumination of a fluorescent tube and are therefore positioned around its perimeter; that evenly spread diodes provide an even spread of ultraviolet light so the glue board has a longer life because its space is used more evenly with reduced likelihood of sections becoming overloaded; and that over a period of twelve months or so light output from a fluorescent tube may reduce by 25 per cent or more whereas no reduction is experienced with diodes, the output of fluorescent tubes reducing significantly over time and thereby reducing attractive power. https://image-ppubs.uspto.gov/dirsearch-public/print/downloadPdf/11369104
3. Seven things to consider when choosing an insect light trap. Commercial pest control company guidance. Trade source with a commercial interest, cited as attributed material. Used for the statement that a wide unit is considered more effective at catching flies than circular or tall and narrow ones due to the shape and orientation of the lamps and the shape of the light emitted, that horizontally orientated lamps emit wide discrete bands of light that flies are attracted towards, and that this is thought to be because it mimics natural shapes of light such as a horizon; for the statement that units used in food-handling businesses should have a glue board or roll rather than an electric grid so that flies are contained hygienically and insect fragments are not scattered around the area by an electric shock; for the statement that the first thing to consider is the difference between units that monitor and units that control a population, which look similar but perform different tasks in premises and areas with varying risks, with monitoring traps usually being glue board units allowing a technician or field biologist to count the catch; and for the framing of monitoring as checking that exclusion equipment and policies such as doors, fly screens and door-policy education are working as they should. https://www.rentokil.com/blog/food-safety/choosing-insect-light-trap
4. LED lamp for insect trap. United States patent specification. Cited as attributed material. Used for the description of ultraviolet light emitted by a fluorescent tube attracting flying insects to the interior of the housing where they adhere to a glue board; for the note that in many traps an electrocution grid is substituted for the glue board and that some traps use insect attracting scents in addition to or instead of the tube; and for the explanation that fluorescent tubes produce light through a reaction involving gases and mercury vapour interacting to produce ultraviolet light, that for general lighting the inside of the tube carries a phosphor coating emitting white fluorescent light, and that this coating is either less densely applied or eliminated altogether in the ultraviolet tubes used in flying insect traps. https://image-ppubs.uspto.gov/dirsearch-public/print/downloadPdf/10986828
5. Turning Ultraviolet Light Traps On and Off Increases Their Attraction to House Flies (Diptera: Muscidae). Journal of Insect Science, 19(1), 22. doi:10.1093/jisesa/iey126. Used for the study design in which pairs of electrocutor-grid ultraviolet light traps were assigned to treatments to evaluate the effects of illumination events on house fly attraction as indicated by numbers of flies captured, with one treatment illuminated constantly and another turned on for one hour then off for one hour repeatedly, giving one illumination event every two hours; for the reported conclusion in the title that turning the traps on and off increases their attraction to house flies; and for the authors' observations that most ultraviolet light trap evaluations are conducted only under laboratory conditions, that studies have also been performed in facilities with high fly densities such as poultry houses which more closely simulate real conditions, and that fly behaviour in relation to the traps has not been fully described in the literature. https://pmc.ncbi.nlm.nih.gov/articles/PMC6377917/
6. Device and method for attracting and trapping flying insects. United States patent specification, experimental examples. Cited as attributed material. Used for the reported experiment in which a trap was outfitted with two diode ultraviolet lights positioned within a few inches of and directed at glue boards, producing a very intense spot on the inside of the housing with a concentration of flies visible in the most intensely lit area and an improved catch achieved by positioning the light sources close to and directed at the glue boards; and for the evaluation of combinations of diodes at 365, 385 and 405 nanometres at constant total power. https://image-ppubs.uspto.gov/dirsearch-public/print/downloadPdf/12250937
7. Insect light trap with extruded curved side panels and curved glue board. United States patent specification. Cited as attributed material. Used for the statement that if the light source is any distance from the glue board, insects attracted to the light source may never meet the glue board and may fly away without being captured, and for the observation that a real need exists for improvements in flying insect trap design in terms of both insect attraction and capture. https://image-ppubs.uspto.gov/dirsearch-public/print/downloadPdf/10798933
8. Insect trap with continuous light pattern. United States patent specification, background section reviewing prior designs. Cited as attributed material. Used for the account of earlier trap designs using an exposed bulb with high voltage electrocuting systems, of exposed ultraviolet emitting light sources with electrified grids for trapping and electrocuting flying insects, of a design in which the insect lands on a grid providing a low voltage pulse that causes it to fly down onto a nontoxic adhesive trapping board which can then be disposed of with the removable sheet, and of designs using exposed bulbs with front facing entry spaces that attract pests to the front of the trap using light directed into a room away from the trap. https://image-ppubs.uspto.gov/dirsearch-public/print/downloadPdf/6959510