Fifteen Square Millimetres: Pantry Pests, Packaging, and the Difference Between Can and Does

1. Introduction: the pest that arrives in a bag

Almost every pest this journal has covered gets in through the building. This one is carried in, sealed, by the occupant, from a shop.

1.1 What this article argues

That the packaging research measures what an insect is capable of, that one source reports infestations arising overwhelmingly by a different route, and that the engineering effort is consequently aimed at the rarer problem. Sections 12 to 14 are the case.

2. The two scenarios

The framing the literature uses.

Two scenarios have been proposed that explain the presence of stored-product insects in packaged foods: (1) insects are present in the product before packaging, or (2) insects invade or penetrate the product after packaging.³

2.1 The first is not a packaging problem at all

If the commodity was infested before it was sealed, no film prevents anything. That is a problem for the mill, the store and the fumigation programme, which our articles on phosphine resistance and on structural fumigation cover.

2.2 The second splits in two

Into penetration and invasion, which §3 defines and which turn out to matter differently than the research volume suggests.

2.3 And a third route the literature assumes

That insects reach the package at all. One source notes that insects can penetrate into packed food items during the dispersal stage, for example during their passage and storing in pantries, or in marketing supplies.⁴

The pantry is named as a site of infestation, not only as its destination.

3. The classification

A clean and genuinely useful distinction.

Insect species are grouped into penetrators that can penetrate packages and invaders that enter packages only through existing holes.²

Stated elsewhere: if they are able to make holes by their sharp mandibles and get entry are called penetrators and most of the times problems come from outside, and if insects are unable to make holes and use some existing opening to enter into packaging are called invaders.⁴

3.1 Why this is a good taxonomy

Because it is functional rather than phylogenetic. It groups species by what they do to a barrier, which is the property that determines whether a barrier works.

This journal has repeatedly complained that pest classifications are organised around what an insect is rather than what it does. This one is not, and §15 is where it runs into trouble.

4. Who is in each group

The membership, as one paper gives it.

Penetrators: adults of Rhyzopertha dominica (F.), Sitophilus oryzae (L.) and Lasioderma serricorne (L.) as well as larvae of Ephestia cautella (Walker) and Plodia interpunctella (Hübner).²

Invaders: adults of Tribolium species, Oryzaephilus species and Cryptolestes ferrugineus (Stephens).²

4.1 In plainer terms

The lesser grain borer, a weevil, the cigarette beetle and the larvae of two moths can get themselves in. The flour beetles, the sawtoothed grain beetle and a flat grain beetle cannot and do not need to.

4.2 The mouthparts are the dividing line

One source describes invaders as insects that typically have weakly developed mouth-parts at both the larval and adult stages.⁷

So the category is a statement about anatomy rather than about behaviour, which is why it should be stable and why §15 finding it unstable is worth noticing.

4.3 And one source names a champion

A 2025 study assessing nine food packages, three each of paper, plastic and aluminium, against five named species identified Rhizopertha dominica as the most effective at penetrating food packaging.¹

5. What the hole looks like

The measurement from §1, examined.

The moth larva removes roughly fifteen square millimetres of film per hole, the two beetles about six, and the sawtoothed grain beetle none, being unable to penetrate.²

5.1 The variance is larger than the mean

Fifteen plus or minus seventeen.² Which means some holes were very much larger than others and the distribution is not symmetric around the average.

We report the figure as published and note that a standard deviation exceeding the mean should temper any use of it as a design parameter.

5.2 A zero is a real result

One of the four species simply could not do it, which is what makes the penetrator and invader distinction a real division rather than a gradient.²

6. The damage that is not a hole

A finding in the same study that changes how a package should be assessed.

The insects also caused mechanical weakening of the film surface by creating multiple small superficial holes covering a 10-20x larger area of the film surface than the penetrated area.²

6.1 Ten to twenty times

So a package showing one entry hole has been worked over across an area an order of magnitude larger, weakened but not perforated.²

6.2 What the superficial holes probably are

Exploratory biting. An insect assessing a surface takes repeated small bites before committing to one location, which would produce exactly the pattern described.²

That is our interpretation rather than the authors' and it is testable: a species that penetrates efficiently should show a lower ratio of superficial to penetrated area than one that struggles. Nobody appears to have reported that ratio by species.

6.3 Which matters for a package still in transit

A film weakened across a wide area will fail more readily to subsequent handling, and the failure will then admit the invaders in §7 who could not have got in themselves.

That inference is ours and it connects the two categories: penetrators manufacture the openings that invaders use.

7. What an invader needs

The dimensions.

Oryzaephilus surinamensis (L.) adults can enter through holes with diameters of more than 0.71 mm, and larvae are capable of invasion through even smaller openings.²

7.1 Seven tenths of a millimetre

Which is smaller than most people would call a hole, and smaller than a great many seam defects and closure gaps.

7.2 Larvae get through less

Which is the stage that matters, because an adult entering lays eggs and a larva entering is already feeding. Both routes establish a population and the smaller aperture is the one that admits the more numerous stage.²

7.3 The risk that follows

One study notes that small holes in commercial plastic packaging present a significant risk, as they can serve as entry points for insects.¹

8. One tenth of a millimetre

And the smaller figure, from a commercial source.

A patent specification states that the newly hatched larvae of invaders typically cause the most damage because they are able to fit through holes as small as 0.1 mm wide.⁷

8.1 That is a pinhole

Not a defect anybody would notice in a shop or at home, and not a defect any reasonable inspection would catch.⁷

8.2 The source is a patent

Arguing for its own sealing method, and flagged accordingly. The figure is consistent in direction with the peer-reviewed statement that larvae invade through smaller openings than adults.²⁷

9. The material question

Which films resist.

One study compared 9 new monolayer and multilayer food-packaging films against four key pests over three months, with the specific objectives of identifying the resistance of new film types, comparing printed and unprinted polypropylene film, and estimating using microscopic image analysis the extent of injury.⁸

9.1 Printed against unprinted

One study set out specifically to compare printed and unprinted polypropylene film.⁸

Which is a good question to have asked. Ink is an additional surface layer with different mechanical properties and possibly different volatile emissions, and a difference either way would matter to every food manufacturer. We did not find the result.

9.2 Material matters and not simply

One account reports that for chocolate packages PP proved effective against the attack of almond moth larvae and Indian meal moth larvae but unlike this polyvinylchloride (PVC) was not effective.⁴

9.2 And the 2025 nine-package study

Assessed three paper, three plastic and three aluminium packages against five species, using cell plate and plastic box tests under laboratory conditions.¹

10. Thickness

The variable everybody agrees on.

One study determined that the thickness of plastic films, particularly polyethylene (PE) and polypropylene (PP), was a critical factor in ensuring package protection.¹

Another reports that relatively more penetrations by insects were in packaging with less thickness, with similar results found for larvae, and that when packaging were used with extra cover these were resistant to insect penetration than when used alone.⁴

10.1 Which is an unexciting finding and a reliable one

Three separate studies converge on it, using different films, different species and different test methods.¹⁴³ That is about as much agreement as this journal encounters anywhere.

10.2 An outer carton is a second barrier

Which is the finding a household can act on and a manufacturer can act on cheaply, and §20 uses it.

11. The energy bar study

A worked example on a specific consumer product.

A study of multilayer polypropylene packages found that the increase in exposure time resulted in an increase in the damage sustained to the energy bars, and that among packaging types, the thickest package was most resilient to penetration by all of the larval stages.³

11.1 The authors' conclusion

That energy bar manufacturers need to invest more effort into improving packaging designs, creating thicker gauge films, or advancing odor barrier technology, in order to prevent penetration and infestation.³

11.2 And the reason it matters commercially

The same paper lists product losses, decreases in consumer confidence, and the possibility of allergic reactions in sensitive individuals, alongside industry costs including fines, penalties by government agencies, the possibility of litigation by consumers who may suffer from eating infested products, and insurance claims.³

11.3 The gap the authors identify

That currently, a limited amount of data are available that scientifically document the insect penetration of commercially packaged food products, especially by the moth in question, described as a common insect pest in retail environments.³

12. The contradiction

And here the literature disagrees with itself in an interesting way.

A patent specification states that invaders, such as Indian meal moths and red flour beetles, account for more than 75% of the infestations of polywoven bags, that invaders commonly enter packages through openings resulting from mechanical damage, defective seals, or holes made by other insects penetrating the package, and that most infestations are the result of invasion through seams and closures, and rarely through penetrations.⁷

12.1 Rarely through penetrations

Against a research literature substantially devoted to measuring penetration.⁷²

12.2 And the routes it names

Invaders enter through openings resulting from mechanical damage, defective seals, or holes made by other insects penetrating the package.⁷

The third of those is §6.2 stated by a source: a penetrator's hole becomes an invader's door, so the two categories are not independent and a package that admits one species subsequently admits others.

12.3 The source and its limits

It is a patent for a bag sealing method, so it has an interest in the conclusion that seams and closures are the problem. And it concerns polywoven bags specifically, which are a bulk commodity package rather than a retail one.⁷

We flag both. The claim is nevertheless specific, quantified and consistent with the geometry in §§7 and 8.

13. Resolving it

The two statements are compatible and the resolution is the point of this article.

A laboratory penetration test presents an insect with an intact film and no alternative. It measures capability.

A real package has a seam, a closure, a fold, a perforation for hanging, and handling damage. It presents an alternative, and the insect takes it.

13.1 So both findings are correct

Indianmeal moth larvae can remove fifteen square millimetres of film, and in practice most of them do not have to.²⁷

13.2 And the test designs say so

One study notes that an earlier published method excludes the possibility of invasion, enabling comparison of the resistance of various film materials to penetration as well as of the separation between invaders and penetrators.⁸

Excluding invasion is the correct experimental design for measuring penetration, and it is precisely why the resulting literature cannot tell you which route dominates in a warehouse.

13.3 Which means the engineering target is wrong

Thicker film addresses the route that is rarely used. Seam integrity and closure design address the route that dominates, and receive less research attention because they are harder to test in a cell plate.

That is our argument and we have not found a source making it.

14. Which is the same finding this journal keeps reaching

For the fifth time, in a fifth literature.

Our boric acid article found an industry association conceding low toxicity and arguing that lack of repellency compensates, because what an insect will accept matters more than what would kill it. Our minimum risk article found strongly repellent compounds that were weakly lethal. Our malaria article found irritancy driving a vector to feed outdoors. Our resistance articles found behavioural avoidance defeating adequate toxicants.

14.1 The general form

What an organism can do and what it does are different measurements, and control depends on the second. A laboratory that offers no alternative measures the first.

Here the same structure appears in a materials science literature with no entomological framing at all, which is why we think it is a real regularity rather than a habit of ours.

15. And the classifications disagree too

A second inconsistency worth recording.

One peer-reviewed source lists adults of Tribolium species among the invaders.² A trade source lists red flour beetle, Tribolium castaneum and confused flour beetle, Tribolium confusum among mid-tier penetrators.⁶

And the patent lists the Indianmeal moth as an invader,⁷ while two peer-reviewed sources classify its larvae as penetrators.²³

15.1 The disagreement has a pattern

Sources describing laboratory capability classify a species as a penetrator. Sources describing field infestations classify the same species as an invader.

Which is §13 appearing as a taxonomic dispute rather than as a research priority. That reading is ours.

15.2 Or the species genuinely varies

The alternative explanation is that penetration ability differs by population, strain, life stage or temperature, and that both classifications are correct for the material each author tested.

We cannot distinguish the two explanations from the sources we have.

15.3 The practical consequence

A category label on a species tells you which paper you are reading rather than what the insect will do to your packet.

16. The warehouse beetle and the allergen

One species with a consequence beyond contamination.

A university stored product protection chapter notes that the warehouse beetle, classified as a penetrator, is more specialized in the food products it infests and is often found in packages of dry pet food and dry pastas, and that it can create an additional problem to the consumer because the cast skins of the larvae can cause allergic reactions.⁵

16.1 Cast skins

Not the insect, the shed exoskeleton, which persists after the population is gone.⁵

Which is exactly the structure our cockroach allergen article described: the protein outlives the animal, so killing the population does not remove the health endpoint. The same logic applies here and to a product people eat.

16.2 Dry pet food

Named specifically.⁵ It is stored in bulk, kept for long periods, often in a garage or utility area, and rarely inspected, which makes it the most commonly overlooked source in a household. That observation is ours.

16.3 Which makes the discard advice a health measure

Not only a control measure. A packet whose population has been killed still contains the cast skins, and for a sensitised person the contamination is the hazard rather than the live insect.⁵

That is our reading, and it is the same conclusion our allergen threshold article reached about a different insect and a different protein.

16.4 And one more strong penetrator

The same chapter describes the drugstore beetle as a strong penetrator.⁵

17. The clothes moth crossover

A finding that links this article to another of ours.

A trade source lists among mid-tier penetrators the webbing clothes moth, Tineola bisselliella, whose larvae are capable of chewing through thin plastic material and paper to get to a source of wool or other animal fibre, illustrating a larva chewing through a thin Low-Density Polyethylene (LDPE) film that is commonly used as grocery bags.⁶

17.1 Which defeats the standard advice

Our article on clothes moths and carpet beetles described storage of woollens in sealed bags as a protective measure. A grocery-weight polyethylene bag is not a barrier.⁶

The thickness finding in §10 applies: the same material at sufficient gauge would hold. The advice should specify a thickness and generally does not, which is our correction.

18. What the industry is trying

The mitigations under development.

One paper notes that manufactures have begun using alternative methods to protect their packaged products such as odor barriers, insect growth regulators (IGR), and insect-resistant packaging.³

Another study examined the effect of repellents on penetration into packaging by stored-product insects.⁸

18.1 Three approaches, three different targets

An odour barrier works on detection, a growth regulator on development, and a resistant film on mechanics.³ Only the third addresses the insect at the package surface.

18.2 Odour barriers are the interesting one

Because they address attraction rather than entry. An insect that does not detect the product does not attempt the package, which is a prevention rather than a barrier.

Our pheromone trap article described how these insects locate resources by volatile cues, and an odour barrier is the same principle used defensively. That connection is ours.

18.2 And insect growth regulators in packaging

Which our article on juvenile hormone and chitin synthesis inhibitors describes.³

19. Which is a treated article

A regulatory observation this journal is now equipped to make.

A packaging film incorporating a repellent or an insect growth regulator is a product treated with a pest control product, whose primary purpose before treatment was not pest control. Our treated articles article set out exactly that definition.³⁸

19.1 Which puts it in the exemption

Treated to protect the article itself, meaning the package and its contents, rather than to protect the user. That is inside the exemption as our earlier article described it.

19.2 And inherits its gap

No efficacy requirement for the treated article, and in most cases no requirement to disclose that the packaging was treated. Which is the same conclusion, arriving at a product people eat from.

We are not aware of any such packaging in general use in Canadian retail and are describing a regulatory category rather than a market. That caveat is ours.

20. What this means for a household

The practical part, which is unusually satisfying because the household can actually solve it.

Find the source. A pantry infestation almost always traces to one item, and the adults seen flying are the end of a cycle rather than the beginning.

Discard rather than treat. The product is the habitat, and there is no circumstance in which applying an insecticide to food is the right answer.

Check the overlooked things. Dry pet food, per §16.2. Also birdseed, decorative dried arrangements, spices, and anything bought in bulk and kept for years.⁵

Clean the shelf. Spilled material in a corner sustains a population after every packet has gone.

And rehouse into rigid sealed containers. Which addresses both routes at once: the wall is thick enough to defeat penetration and the seal has no seam gap for invasion.¹⁷

20.1 The one step people skip

Cleaning the shelf. Every other step removes a packet, and a population that has been in place long enough to be noticed has usually deposited material outside the packet as well.

Our article on cockroach allergen abatement found that the intervention which worked combined bait with professional cleaning, and that killing the insects did not remove what they had left. The same two-part structure applies here at domestic scale.

21. Why a treatment is usually the wrong purchase

Stated plainly, at commercial cost to us.

The insects are inside food. A residual application to a kitchen surface does not reach the population, and an application near food is inappropriate regardless of whether it would.

21.1 What a spray actually achieves

It kills adults that walk across it, which are the dispersing stage and not the reproducing population inside the packet. The client sees fewer moths for a few days and then sees them again.

Our articles on treatment failure and on rebound describe that sequence, and our credence goods article explains why a client cannot distinguish it from a treatment that did not work.

21.2 And the thing a client actually wants

Reassurance that the food they have eaten was not harmful and that the problem will end. Neither is delivered by a treatment, and both are delivered by an explanation and a competent search of the pantry.

Our article on the psychological burden of infestation describes why the reassurance matters as much as the control, and this is a case where it is most of what is being asked for.

21.3 So the honest answer is a diagnosis

Which is a smaller sale than a treatment and is the correct one.

22. When a contractor is genuinely needed

Because sometimes one is.

When the source cannot be found. A persistent population with no identified item usually means a spillage in a void, a forgotten container, a rodent cache or a dead animal, and finding it is the job.

When the species is unclear. The response differs between a fabric pest, a food pest and something arriving from outside, and our article on identification accuracy explains why that call is harder than it looks.

In a commercial premises. Where the scale, the regulatory exposure and the stock value change the calculation entirely, and our fumigation and stored grain articles apply.

And where the same problem recurs. Repeated reinfestation from purchased goods points at a supplier rather than at a kitchen.

22.1 That last case is the interesting one

Because it is not a pest control problem at the property. It is a procurement problem, and the useful output is a record of which products arrived infested and when.

Our article on pheromone trap catch interpretation describes the monitoring that would generate that record, and it is the one place in this subject where a formal programme earns its cost.

23. Our own position

The disclosure.

We are a pest control contractor and a pantry moth call is a callout we could bill. Section 21 says that in most cases the work is a diagnosis and a conversation rather than a treatment, and that is what we would sell.

23.1 Why say so

Because a client who is told to throw out a bag of flour and clean a shelf, and whose problem then ends, is a client who will call again about something that does need treating.

That is a commercial argument as well as an honest one and we state it as both.

24. The Manitoba position

Two local notes.

The grain connection. This province handles and stores a great deal of grain, and our phosphine resistance article concerns the industrial end of the same insect group. The domestic pantry problem and the elevator problem share a species list.

And the season. A long indoor winter with heating means stable warm conditions in a kitchen for months, which is the developmental environment these species need and do not get outdoors here.

24.1 And the cold option

A freezer is the one control measure a household in this climate has abundantly, and freezing infested but valuable goods is standard advice. We did not locate time and temperature data for these species in this search, and our article on thermal disinfestation covers the principle for a different pest.

Which is a gap we would want filled before recommending a specific regime.

24.2 What we could not find

Any Canadian data on the frequency of retail stored product infestation, any Manitoba species survey, and any figure for how often a domestic complaint traces to purchased goods rather than to a residual population.

25. Limitations and open questions

Most sources were read as abstracts. The penetration measurements, the film comparisons and the classification lists all reach us through published abstracts and extracts rather than full papers.²¹

The central contradiction rests on a patent. The 75 per cent figure and the seams and closures claim come from a document arguing for its own sealing method, and we found no peer-reviewed corroboration.⁷

And it concerns one bag type. Polywoven bulk bags, not retail packaging.⁷

The variance on the headline figure is large. Fifteen plus or minus seventeen square millimetres, per §5.1.²

One source is a trade blog. The mid-tier penetrator list and the clothes moth illustration come from a commercial supplier of monitoring products.⁶

We found no efficacy data for treated packaging. Odour barriers, growth regulator films and repellent-treated films are described as being tried and not as being demonstrated.³⁸

And we did not cover the species biology. Development times, temperature thresholds and generation counts are absent here, and a reader wanting to know how fast a population builds will not find it in this article.

Sections 1.1, 2.3, 3.1, 5.1, 6.2, 8.1, 13, 14, 15.1, 16.2, 17.1, 18.1, 19, 20, 21, 22 and 24 are our reasoning. The capability against behaviour argument and its consequence for engineering priorities, the reading of the classification dispute, the penetrators-make-holes-for- invaders point, the treated article observation, the clothes moth correction and the practical advice are ours rather than sourced positions.

26. Conclusion

The packaging literature divides these insects functionally, into penetrators that make their own hole and invaders that use one already there, and it measures the difference: fifteen square millimetres of film per hole for Indianmeal moth larvae, six for a weevil and a grain borer, and none at all for the sawtoothed grain beetle, whose adults instead enter through gaps larger than seven tenths of a millimetre.² Film thickness is the variable everybody agrees on, an outer carton doubles the barrier, and the damage extends across an area ten to twenty times the hole itself.¹⁴²

And a patent reports that invaders account for more than seventy-five per cent of infestations in one bag type, and that most infestations result from invasion through seams and closures rather than penetrations at all.⁷ Both can be true, because a laboratory test offers an intact film and no alternative while a real package offers a seam. The literature measures what these insects can do and infestations are produced by what they do, which is the fifth time this journal has arrived at that distinction from a fifth direction, and the first time in a materials science literature with no entomology in it.

For a household the practical consequence is unusually good news. The source is almost always one purchased item, the remedy is to find it and throw it out rather than to treat anything, the overlooked container is the dry pet food, and rigid sealed storage defeats both entry routes at once. A contractor called to a pantry moth problem is being asked for a diagnosis, and selling a treatment instead is selling something that reaches the flying adults and not the population inside the packet.

References

1. Comparison of the resistance of various food packaging materials to stored product insect pests. Journal article in a stored products research title, read as abstract. Used for the study design assessing the resistance of nine different food packages, three each of paper, plastic and aluminium, to common stored-product insect pests including four named beetle species and the larvae of a named moth, tested under laboratory conditions using cell plate and plastic box tests; for the finding that one named grain borer was the most effective at penetrating food packaging; for the statement that small holes in commercial plastic packaging present a significant risk as entry points for insects; and for the determination that the thickness of plastic films, particularly two named polymers, was a critical factor in ensuring package protection. https://www.sciencedirect.com/science/article/abs/pii/S0022474X25002401
2. Barrier property and penetration traces in packaging films against a named moth larva and a named beetle adult. Journal article in a stored products research title, read as abstract. Used for the statement that stored-product insects frequently infest packaged food causing significant monetary losses to industry and consumers; for the study comparing the resistance of nine new monolayer and multilayer packaging films to four key pests over three months; for the measured differences in chewing capacity and entrance hole size, namely 15 plus or minus 17 square millimetres of penetrated area per hole for the moth larvae, 6 plus or minus 5 for one weevil, 6 plus or minus 2 for the grain borer, and no penetration by the sawtoothed grain beetle; for the finding that insects also caused mechanical weakening of the film surface by creating multiple small superficial holes covering an area ten to twenty times larger than the penetrated area; for the classification of species into penetrators that can penetrate packages and invaders that enter only through existing holes, with named species assigned to each; and for the report that adults of the sawtoothed grain beetle can enter through holes with diameters greater than 0.71 millimetres while its larvae are capable of invasion through even smaller openings. https://www.sciencedirect.com/science/article/abs/pii/S0022474X11000154
3. Evaluating penetration ability of a named moth larva into multilayer polypropylene packages. Open-access journal article. Used for the statement that the presence of stored-product insects in ready-to-eat packaged products causes product losses, decreases in consumer confidence and the possibility of allergic reactions in sensitive individuals, with industry losses including fines, penalties by government agencies, possible litigation by consumers and insurance claims; for the note that manufacturers have begun using alternative protective methods such as odour barriers, insect growth regulators and insect-resistant packaging, and that creating insect-resistant packaging requires understanding the mechanisms by which insects penetrate; for the statement that a limited amount of data scientifically documents insect penetration of commercially packaged food products, especially by the named moth described as a common pest in retail environments; for the two proposed scenarios explaining the presence of these insects in packaged foods, namely presence before packaging or invasion or penetration afterwards; and for the findings that increased exposure time increased damage sustained and that among packaging types the thickest package was most resilient to penetration by all larval stages, with the authors concluding that manufacturers should invest in improved designs, thicker gauge films or advanced odour barrier technology. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6023371/
4. Evaluation of standard loose plastic packaging for the management of two named stored product beetles. Open-access journal article in an insect science title. Used for the statement that insects can penetrate packed food items during the dispersal stage, for example during passage and storing in pantries or in marketing supplies, and that insects and their contaminants are also carriers of microorganisms; for the definitions that insects able to make holes with sharp mandibles are called penetrators, with problems most often coming from outside, while those unable to make holes and using an existing opening are called invaders; for the observation that the properties of plastic packing materials vary against penetration, with one named polymer proving effective against two named moth larvae in chocolate packages while another named polymer was not; and for the reported results that relatively more penetrations occurred in packaging of lesser thickness, that similar thickness effects were found for larvae, and that packaging used with an extra cover was more resistant than when used alone. https://academic.oup.com/jinsectscience/article/16/1/91/2726708
5. Insect-resistant packaging chapter, university stored product protection reference volume. Used for the tabular classification of pests that commonly infest packaged food, naming the red flour beetle, confused flour beetle, sawtoothed grain beetle, almond moth larvae and Indianmeal moth larvae among others; for the description of the warehouse beetle as classified as a penetrator, more specialised in the food products it infests, often found in packages of dry pet food and dry pastas, and creating an additional problem for the consumer because the cast skins of the larvae can cause allergic reactions; and for the description of the drugstore beetle as a strong penetrator. https://entomology.k-state.edu/doc/finished-chapters/s156-ch-12-ins-resistant-packaging-mar-14.pdf
6. Stored product insects chewing their way into our lives, blog article by a supplier of monitoring products for these pests. Commercial trade source, cited as attributed material. Used for the listed mid-tier penetrators including the larval stages of a named moth, a flour moth, an almond moth, the red flour beetle, the confused flour beetle, the warehouse beetle, the black carpet beetle and others; for the statement that webbing clothes moth larvae are also a mid-range penetrator capable of chewing through thin plastic material and paper to reach a source of wool or other animal fibre, illustrated by a larva chewing through a thin low-density polyethylene film of the kind commonly used for grocery bags; and for the note that there is also a group of low-tier penetrators that are not good at chewing through packaging but are good at finding ways through that do not require chewing. https://www.insectslimited.com/blog/stored-product-insects-chewing-their-way-into-our-lives
7. Triple-folded hot air sealed thermoplastic bags. Patent specification for a bag sealing method. Commercial advocacy for the claimed invention, flagged accordingly and having a direct interest in the conclusion that seams and closures are the principal entry route. Used for the statement that many closures of polywoven bags form holes that can allow insects and their larvae to enter; for the description of invaders as insects typically having weakly developed mouthparts at both larval and adult stages; for the claim that invaders, naming two species, account for more than 75 per cent of the infestations of polywoven bags; for the statement that invaders commonly enter through openings resulting from mechanical damage, defective seals, or holes made by other insects penetrating the package; for the report that newly hatched larvae of invaders typically cause the most damage because they can fit through holes as small as 0.1 millimetres wide; and for the conclusion that most infestations result from invasion through seams and closures, and rarely through penetrations. https://image-ppubs.uspto.gov/dirsearch-public/print/downloadPdf/10604322
8. The effect of repellents on penetration into packaging by stored-product insects. Research repository record for a journal article, read as abstract. Repository listing rather than the primary paper. Used for the study aim of comparing the resistance of nine types of film, porous filter paper and one type of plastic cup to infestation by four common stored-product and finished-food insect pests, comprising the adults of three named beetle species and the larvae of a named moth; for the use of modified standard penetration and invasion tests drawn from earlier published methods; for the stated objectives of identifying the resistance of new monolayer and multilayer films, comparing printed and unprinted polypropylene film, and estimating by microscopic image analysis the extent of injury caused by various pest species; and for the note that one earlier method excludes the possibility of invasion, enabling comparison of film resistance to penetration as well as separation between invaders and penetrators. https://www.researchgate.net/publication/228498312_The_effect_of_repellents_on_penetration_into_packaging_by_stored-product_insects