Knocked Down Is Not Dead: What a Quick Kill Claim Measures

1. Introduction: two words doing one job

Kills on contact. Quick kill. Rapid knockdown. These appear on the same products and are read as the same claim.

1.1 Distinct performance endpoints

Which is the phrase to hold on to, and it comes from the study's own conclusion.³

1.2 What this article argues

That the two endpoints separate for one pyrethroid class and not the other, that the class boundary is a threshold on a continuum whose cut point is species-dependent, and that the temperature relationship runs opposite to intuition. Sections 5, 17 and 22 are the case.

2. The mechanism

Stated first, because everything follows from it.

The primary mechanism of pyrethrins and pyrethroids is prolonged activation and opening of voltage-dependent sodium channels, resulting in a tail current and prolonged depolarization, with Type II compounds more potent and causing a more prolonged depolarization.¹

2.1 The channel is held open rather than blocked

Which distinguishes this from our fipronil article, where the compound blocked a channel that should have been passing current. Here a channel that should have closed does not.

2.1b Which is the opposite kind of interference

Blocking a channel removes a signal. Holding one open adds signal that should have stopped, and the animal is poisoned by its own nervous system running on rather than by anything being silenced.

2.2 And the consequence is excitation

Compounds without an alpha-cyano group retain sodium channels in a modified open state only transiently, cause large depolarizing afterpotentials, and evoke repetitive firing with minimal effect on the resting potential.⁷

3. What knockdown is

A neurological state produced by that excitation.

The insect loses coordinated control and cannot remain upright or move purposefully. It is observable, fast, and easy to score, which is why it became a measurement.

3.0b And it is unusually easy to measure

Knockdown is binary, visible to the naked eye, happens within minutes, and requires no dissection, no chemistry and no waiting. Mortality requires a holding period, a definition of death that distinguishes it from moribundity, and a decision about how long to wait before scoring.

Which is a sufficient explanation for why knockdown became the convenient endpoint without anybody having decided it was the right one. That is ours.

3.1 And it is genuinely what the compound was selected for

The class is used partly because it acts quickly, which matters for a flying insect in a room and for a customer watching.

4. And what it is not

It is not a physiological endpoint.

An animal lying on its back with its nervous system firing repetitively has not yet been established to be dying, and the question of whether it will is a separate one.

4.1 Which sounds obvious when stated

And is nevertheless what most rapid-action claims depend on the reader not separating.

That observation is ours; §§5 and 6 supply the evidence.

5. The 2026 finding

From a study following individual flies by computer vision.

Rapid knockdown by type-I pyrethroids did not consistently predict individual mortality, potentially leading to misconceptions regarding product label claims such as 'quick kill' or 'kills on contact'.²

5.1 And the contrast within the same experiment

A strong knockdown-mortality correlation was observed for an individual Type II pyrethroid and for organophosphate insecticides.²

5.2 Which the authors describe as new

Stating that to their knowledge the study demonstrates for the first time that the relationship between knockdown speed and mortality at the individual level varies significantly among insecticide classes.²

5.3 At the individual level

Which is the methodological point that makes it possible: tracking whether the particular animal that went down quickly is the particular animal that died, rather than comparing group percentages.

That reading is ours, and it explains why computer vision was required.²

6. Which the authors state as a regulatory problem

In terms we would not have dared put more strongly.

This distinction carries significant regulatory implications. If rapid knockdown observed at the designated time point does not reliably predict ultimate mortality for type-I pyrethroids, then employing knockdown as an indicator for lethality in product claims may misrepresent the efficacy of these products, unlike for type-II pyrethroids and organophosphates.²

6.1 May misrepresent the efficacy

Which is a claim about registration practice rather than about chemistry.²

6.2 And it bears directly on our consumer products article

Which assessed household aerosols and found the efficacy evidence thin. This supplies a mechanism for one specific way the impression of efficacy is generated: the consumer observes knockdown, which is real, and infers mortality, which may not follow.

7. The proposed explanation

Offered by the authors as a possibility.

Metabolic recovery. In the case of Type I pyrethroids, rapid knockdown is often caused by acute neuroexcitation due to sodium channel modulation, and subsequent recovery is feasible if an insect possesses sufficient metabolic capacity to detoxify the compound after knockdown.²

7.1 So knockdown starts a clock rather than ending one

The animal is incapacitated and simultaneously processing the compound, and which finishes first determines the outcome.

7.2 Which makes the outcome depend on the individual

Two animals receiving identical doses can diverge on the strength of metabolic capacity alone, which is the quantity that varies most within a population.

That inference is ours and it connects this to our synergist and metabolic resistance articles.

8. Why it is class-specific

Our reading of why Type II behaves differently.

If recovery requires the compound to be cleared before the neurological insult becomes fatal, then a compound producing a much longer depolarization gives metabolism less opportunity to win the race.¹

8.1 Which is the same shape as our cuticular resistance argument

Where the barrier mattered because it gave enzymes more time. Here the compound's channel kinetics determine how much time the enzymes get.

8.2 We offer this as an interpretation

The paper proposes metabolic recovery and reports the class difference; the link between channel kinetics and the size of the recovery window is ours.

9. The mixture result

Which the paper's title is built around.

A synergistic mixture of two Type I compounds showed enhanced toxicity and the advent of the knockdown-mortality relationship, described as a synergistic transition from Type-I-like to Type-II-like symptomology.²

9.0b Synergy here means more than additive toxicity

Two compounds can be synergistic in the ordinary sense, where the mixture kills more than the sum of its parts, without either changing character. What is reported here is that the mixture also acquired a property neither component had, namely the correlation between how fast an animal went down and whether it subsequently died.²

9.1 Two Type I compounds behaving as a Type II

Both named compounds belong to the Type I group individually, and the mixture did not.²

10. Which is the most interesting part

Our assessment.

The class assignment is supposed to be a property of the molecule, determined by whether it carries a cyano group.¹ A mixture of two molecules that each lack one produced the behaviour of molecules that have one.

10.1 So the syndrome is a property of the exposure

Rather than of any single compound in it, at least under combination, and §§13 to 17 suggest why that is less surprising than it first appears.

10.2 And it has a practical edge

Household products commonly contain more than one pyrethroid. Whether a given formulation behaves as Type I or Type II is therefore a question about the formulation and not answerable from the ingredient list alone.

That is ours.

11. What this means for a product claim

Three things, following from §§5 and 6.

A knockdown claim is a true claim about a real effect. Nothing here says otherwise.

A kill claim substantiated by knockdown data is a different matter.²

And the difference is class-dependent. The same substantiation method is sound for a Type II compound and unsound for a Type I.³

11.1 And the asymmetry is worth naming

A registrant substantiating a kill claim with knockdown data is not necessarily doing anything improper, because for much of the chemistry in use the two track each other closely. The problem is that the substantiation method is sound for some actives and unsound for others, and nothing in the claim itself indicates which case applies.

12. And for a bioassay

Which is where it touches our resistance articles.

Resistance monitoring frequently scores knockdown at a fixed interval because it is fast and unambiguous.

12.1 For Type I compounds that scores the wrong endpoint

A population with high metabolic capacity would knock down normally and recover, appearing susceptible on a knockdown-scored assay and resistant on mortality.

12.1b And the error runs in the direction least likely to be noticed

An assay that overstates resistance prompts investigation, because somebody has to explain a control failure. An assay that understates it produces a reassuring result nobody queries, and the programme continues using a product that is failing in the field for a reason the monitoring was designed to detect.

12.2 Which is a second way a bioassay can mislead

Our cuticular resistance article described one, where the barrier is inside the resistance ratio. This is another, where the endpoint measured is not the endpoint of interest.

Both are ours and both point the same way: a single number from a standard assay compresses more than it appears to.

13. The two classes, defined

Since the argument has been leaning on them.

Type I pyrethroids are chemicals without a cyano group; Type II are those with a cyano group. Compared to Type I, Type II compounds are generally more potent, environmentally persistent and toxic to humans.¹

14. Where the division came from

Which is worth knowing because it was not a chemical classification.

Pyrethroids were historically classified into two subclasses based on induction of either the T syndrome, whole body tremor, or the CS syndrome, choreoathetosis with salivation, following intravenous or oral administration to rats at near-lethal dose levels.⁶

14.1 The T syndrome described

Aggressive sparring, sensitivity to external stimuli, fine tremor progressing to whole body tremor and prostration, with elevation in core body temperature attributed to excessive muscular activity associated with tremor.⁶

14.1b Which is a syndrome described in a mammal

Nothing in that description concerns an insect, and the terms are clinical: tremor, salivation, prostration, core temperature. The classification that structural pest control uses to group its principal insecticides was built from the appearance of poisoned rats.⁶

14.2 And the chemical correlate came afterwards

Data published in the 1980s showed CS syndrome was almost exclusively produced by pyrethroids containing a cyano linkage at the central ester structure and T syndrome almost exclusively by those without.¹

14.3 So a structural feature was fitted to a behavioural observation

In rats, at near-lethal doses, by a route nothing encounters in the field. The classification has served well and its origin is worth remembering when it is asked to do work at the edges.

That last sentence is ours.

15. The compounds that sit between

And there are named ones.

One analysis groups several compounds into one mechanism group and several into a second, while two named compounds occupy an intermediate position between the two groups.⁶

15.1 Intermediate is not a third class

Pyrethroids producing transitional values tend to result in mixed-type clinical signs, which may indicate simultaneous occurrence of both syndromes rather than a distinct third one.⁶

16. The time constant

Which is what the classification actually cuts, and the number is specific.

The transition between the two syndromes corresponds to a time constant of about 200 milliseconds in the frog and 10 milliseconds in the rat.⁶

16.1 A twentyfold difference between two species

In the value at which a compound stops behaving as one type and starts behaving as the other.⁶

17. Which makes the class partly a property of the animal

Our conclusion from §16.

If the boundary sits at a different value in different species, then a compound whose kinetics fall between those values is a Type I compound in one animal and a Type II compound in another, without changing at all.

17.1 And the two species quoted are both vertebrates

Neither is an insect, and we found no statement of where the critical value sits in any pest species.⁶

17.1b And insects are not at 37 degrees

Channel kinetics are temperature-dependent, as §23.2 reports, so a time constant measured in a warm-blooded animal and a time constant in an insect at ambient temperature are not measured under comparable conditions even before the species difference is considered.⁵

17.2 Which is a gap with practical weight

Because §5's finding is about which class a compound belongs to, assessed in a house fly, using a classification whose threshold was established in mammals.

We raise this as a question rather than an objection. It may be that the assignment is stable across the relevant species and nobody thought it needed saying.

18. And the sources disagree about the binding site

Which bears on whether the two classes are different in kind or in degree.

One source holds that research on knockdown resistance and modelling of pyrethroid binding to the sodium channel lend support to the existence of unique binding sites for the Type I and Type II compounds.⁶

18.1 The other holds the opposite

Reporting that effects of the phenoxybenzyl pyrethroids were intermediate between the two extremes, suggesting a continuous variation in the kinetics with which pyrethroids and DDT analogues modify sodium channels, and stating that it was not necessary to assume a second site of action to account for the variability observed.⁷

19. Which we report unresolved

As we did with the selectivity contradiction in our fipronil article.

One position implies two discrete mechanisms; the other implies one mechanism with continuously varying kinetics. The second is the more parsimonious and the first has binding models behind it.⁶⁷

19.1 We are not in a position to adjudicate

Both sources reach us as abstracts, we have not seen the binding models, and the two may be separated by publication date rather than by genuine disagreement.

19.2 But the practical reading is the same either way

The two-class scheme is a useful summary of a graded property and should not be expected to behave like a natural kind, which is what §§10, 15 and 17 each demonstrate from different directions.

20. The other targets

Because the sodium channel is not the only one.

Pyrethrins and pyrethroids also act as antagonists at GABA chloride channels within the central and peripheral nervous system.¹

20.1 Which is the channel our fipronil article was about

Making pyrethroids and fipronil partial overlaps at a target the mode-of-action classification treats as belonging to a different group entirely.

20.2 And calcium channels as well

Pyrethroids have been shown to act on isoforms of voltage-sensitive calcium channels, contributing to neurotransmitter release, with evidence that action at sites other than the sodium channel may contribute to their effects in a living animal.⁶

20.2b And it bears on the synergist literature too

A compound acting at three channel types has three opportunities to be affected by anything that changes its concentration or its residence time in the animal, which is part of why synergist results with this class are harder to interpret than the single-target account suggests.⁶

20.3 Which is a recurring pattern in this journal

Our fipronil article found a second target that rescued the compound from an expected cross-resistance. Here the second and third targets complicate a classification built on the first.

21. The temperature coefficient

And this is the part with direct local relevance.

Most insecticides become more toxic as temperature rises. Pyrethroids are the standard exception, and the exception has a name.

22. The insect evidence

From a study across three temperatures.

Knockdown, toxicity and resistance to four compounds were examined in house flies at 18, 25 and 32 degrees in a susceptible strain, a strain with a known knockdown resistance mechanism, and a multiply resistant strain. All four pyrethroids showed greater kill at 18 than at 32°C, although the differences varied with the compounds and, to a lesser extent, with the strains.⁴

22.1 All four

Including two that carry a cyano group and would be classed as Type II.⁴

22.2 And knockdown behaved separately again

Penetration and recovery from knockdown occurred more rapidly at higher temperatures.⁴

22.2b Which is two separate temperature effects in one sentence

Penetration and recovery both accelerated with warmth. The first should increase toxicity and the second should decrease it, and the reported kill went down, so whatever penetration contributed was outweighed.⁴

22.3 Which is §5's decoupling visible in a study forty years earlier

Faster recovery from knockdown at the temperature where kill was lower, in the same experiment. The connection is ours; the 2026 paper does not cite it.⁴

23. Why it runs that way

The study attributes it to two causes.

Rate of metabolism, excretion and redistribution, and reactivity at the site of action. The negative coefficient of two compounds appears due to both, while that of the other two is likely due primarily to increasing metabolism, excretion and redistribution with increasing temperature.⁴

23.1 So warmth helps the insect more than it helps the compound

Faster metabolism clears more, faster penetration delivers more, and the first dominates empirically.

23.2 And the target contribution is independently supported

Work on mammalian neurons reports that the action of pyrethroids on sodium channels is temperature-dependent and that sensitivity can be augmented by lowering the temperature, with lowering from 37 to 22 degrees producing a 2.6-fold increase in potency for deltamethrin-induced calcium influx.⁵

24. And the mammalian literature says something different

Which we noticed while assembling §21.

A clinical reference states that Type I pyrethroids have a negative temperature coefficient, indicating higher potency at temperatures lower than normal human temperature, while type II pyrethroids have a positive temperature coefficient, are more potent at higher temperatures, and are thus more likely to cause toxicity in humans.¹

24.1 Which conflicts with §22.1 on its face

The house fly study reports greater kill at the lower temperature for compounds of both types, and the clinical reference assigns the two types opposite signs.¹⁴

24.2 And §23.2 sits on the third side of it

Reporting increased potency at lower temperature for a Type II compound, in mammalian neurons.⁵

25. Which we also report unresolved

With one candidate reconciliation.

The clinical classification concerns human toxicity, the house fly work concerns insect kill, and the two literatures may be describing different organisms in which the balance between metabolism and target interaction falls differently.

25.1 That would make both statements true in their own domain

And would mean the temperature coefficient is not a property of the compound at all.

25.2 It is a guess

Ours, unsupported by any source we found, and offered because a reader encountering both statements deserves to know they conflict rather than to be given one.

26. The selectivity figure

Recorded for the same reason our other chemistry articles record theirs.

Insect voltage-dependent sodium channels have greater sensitivity to pyrethroids, and these compounds are approximately 2000 times more toxic to insects than to humans.¹

26.1 Which is a large margin by any standard

Larger than the figures our fipronil article reported.¹

26.1b And it is a margin with an unusual basis

Most selectivity in this journal has come from a structural difference at a target, a metabolic difference, or a placement difference. A margin that depends partly on the two organisms being at different temperatures is none of those, and it would narrow in any setting where the insect is warm.

26.2 And part of it is temperature

A compound more potent below human body temperature is being used against animals that are at ambient temperature, which contributes to a margin usually attributed to receptor differences alone.

That inference is ours and it follows from §§23.2 and 24.

26.3 With a route note

Less than 2 per cent of one Type II compound is absorbed dermally, which our applicator exposure article would want alongside its glove findings.¹

27. What follows for cold-climate work

Our reading, and it is the local payoff.

Structural work here routinely happens in unheated or partly heated spaces: attics in autumn, crawlspaces, garages, loading docks, vacant units with the heat turned down.

27.1 The insect evidence says the compound performs better there

Greater kill at 18 than at 32 degrees, across four compounds and three strains.⁴

27.2 Which inverts the usual expectation

That cold conditions degrade treatment performance. For this class the direction appears to be the other way within the range tested.

27.2b And it may explain an observation technicians already make

That treatments in cool conditions sometimes appear to work better than the same product applied in summer heat, which is ordinarily attributed to slower evaporation, longer residue life or reduced insect activity.

The temperature coefficient supplies a fourth candidate explanation operating at the nerve itself. We are not claiming it is the operative one, only that it is absent from the list a technician would normally reach for.

27.3 With two limits we want stated immediately

The range tested was 18 to 32 degrees, which says nothing about behaviour near freezing; and insects at low temperature are less active, so contact with a treated surface may fall even as the compound's potency rises.⁴

The second point is ours and it may cancel the first entirely in a residual treatment, where efficacy depends on the animal walking across the deposit.

28. What we would change in practice

Two things, both modest.

Do not report knockdown as a result. A technician who sees insects drop during a treatment has observed something real and not the outcome the customer is buying.³

And treat a post-treatment sighting differently. Live insects found two days after an application are consistent with recovery rather than with missed harbourage, and the two call for different responses.

28.1 Which is a diagnostic distinction we have not been making

And we are not aware of any way to separate the two in the field, so this is a caution rather than a method.

29. Our own position

The disclosure.

Pyrethroids are the backbone of structural treatment and we use them constantly. An article arguing that their most visible effect is not the effect being sold is an argument against a reassurance our own technicians give on site.

29.1 And it cuts toward professional application rather than away

Since the products most reliant on visible rapid knockdown are consumer aerosols, and §6.2 says the impression they create has a mechanism. We note that this conclusion is convenient for us and believe it is correct anyway.

30. The Manitoba position

30.1 What we could not find

Any study of pyrethroid performance at the temperatures that characterise unheated space in this climate, any Canadian registration guidance on knockdown versus mortality as substantiation, and any local resistance data of the kind §12 says would be affected by endpoint choice.

30.1b And one comparison that would be cheap to run

The same product, the same species, the same exposure period, scored at knockdown and again at mortality after a holding period, in a heated and an unheated space. That is a within-firm exercise rather than a study, and it would test both of this article's practical claims at once.

30.2 The first is the one worth having

Because §27's range stops at 18 degrees and a great deal of structural space here sits below that for much of the year.⁴

31. Limitations and open questions

The central paper was read as abstract and extracts. We have the conclusions, the proposed explanation and the mixture result, but not the methods, the doses, the number of individuals tracked or the statistical treatment.²³

It is one species. House flies, which are the standard test organism for knockdown precisely because knockdown is easy to score in them, and we did not establish whether the decoupling appears in cockroaches or bed bugs.²

That is the most important gap because §§11, 12 and 28 generalise from one species to product claims, bioassays and field practice respectively.

The temperature study is old. It reaches us as an abstract of work published decades ago, using compounds and strains of that period, and we did not find a modern replication.⁴

Two contradictions are left standing. The binding site question in §19 and the temperature coefficient sign in §25, both because our sources conflict and we could not obtain the full texts that might settle them.¹⁴⁶⁷

One source is a clinical reference work. Written for treating human poisoning rather than for insect toxicology, which is the likely origin of the framing difference in §25.¹

Sections 4, 5.3, 7.2, 8, 10, 12, 14.3, 17, 19.2, 20.3, 25, 26.2, 27.3 and 28 are our reasoning. The knockdown-is-not-an-endpoint framing, the channel-kinetics explanation for the class difference, the argument that the class boundary is partly a property of the animal, the bioassay consequence, the temperature contribution to the selectivity margin and the activity objection in §27.3 are ours rather than sourced positions.

32. Conclusion

Pyrethroids hold voltage-dependent sodium channels open, producing a tail current and prolonged depolarization, with Type II compounds causing a longer depolarization than Type I.¹ The visible consequence is knockdown, which is a neurological state rather than an endpoint. A 2026 study following individual house flies reports that rapid knockdown by Type I pyrethroids did not consistently predict individual mortality, while a strong knockdown-mortality correlation held for a Type II compound and for organophosphates, and the authors say plainly that knockdown speed should not be used as a proxy for lethality for Type I compounds and that claims such as quick kill or kills on contact may misrepresent these products.²³ The proposed explanation is metabolic recovery after knockdown, which makes the outcome a race between incapacitation and detoxification.²

The two-class scheme carrying that argument turns out to be a threshold on a continuum. It began as two syndromes observed in dosed rats and acquired its chemical correlate afterwards; named compounds occupy an intermediate position; the transition corresponds to a time constant of about 200 milliseconds in the frog and 10 in the rat, which means a compound between those values would be one type in one animal and the other type in another; and a mixture of two Type I compounds produced Type-II-like behaviour including the appearance of the knockdown-mortality relationship.⁶² Sources also disagree about whether the types occupy distinct binding sites, which we leave unresolved.⁶⁷

The temperature relationship runs backwards from the usual expectation. All four compounds in one house fly study killed better at 18 degrees than at 32, attributed to metabolism, excretion and redistribution speeding up with warmth and to changes at the target, with recovery from knockdown also faster when warmer.⁴ A clinical reference assigns the two types opposite temperature coefficients, which conflicts with that and which we report rather than reconcile.¹ For work in unheated space in this climate the insect evidence points one way and an obvious objection points the other, since a cold insect walks across fewer treated surfaces. What we take from all of it is narrower than any of the individual findings: the thing a technician and a customer both watch happen is not the thing either of them is paying for.

References

1. Pyrethrin and pyrethroid toxicity. Clinical reference chapter in an open medical resource, written for the management of human poisoning rather than for insect toxicology, which we flag because it is the likely origin of one framing difference this article reports. Source for the primary mechanism as prolonged activation and opening of voltage-dependent sodium channels resulting in a tail current and prolonged depolarization, with Type II compounds more potent and causing a more prolonged depolarization; for the statement that insect voltage-dependent sodium channels have greater sensitivity and that these compounds are approximately 2000 times more toxic to insects than humans; for the statement that Type I compounds have a negative temperature coefficient indicating higher potency below normal human temperature while Type II compounds have a positive temperature coefficient, are more potent at higher temperatures and are thus more likely to cause toxicity in humans; for the statement that pyrethrins and pyrethroids also act as antagonists at GABA chloride channels in the central and peripheral nervous system; for the history that data published in the 1980s showed the CS syndrome almost exclusively produced by pyrethroids containing a cyano linkage at the central ester structure and the T syndrome almost exclusively by those without, and that today Type I refers to chemicals without a cyano group and Type II to those with one, with Type II generally more potent, environmentally persistent and toxic to humans; and for the dermal absorption figure of less than 2 per cent for one named Type II compound. https://www.ncbi.nlm.nih.gov/books/NBK606124/
2. Synergistic transition from type-I-like to type-II-like symptomology in a pyrethroid mixture and its impact on knockdown-mortality relationships in Musca domestica. Journal article in a pest management title, read as publisher extracts rather than in full. Source for the finding that rapid knockdown by Type I pyrethroids did not consistently predict individual mortality, potentially leading to misconceptions regarding product label claims such as quick kill or kills on contact; for the contrasting observation of a strong knockdown-mortality correlation for an individual Type II pyrethroid and for organophosphate insecticides; for the authors' statement of the regulatory implication, that if rapid knockdown at the designated time point does not reliably predict ultimate mortality for Type I pyrethroids then employing knockdown as an indicator for lethality in product claims may misrepresent the efficacy of these products; for the proposed explanation of metabolic recovery, namely that rapid knockdown by Type I compounds is often caused by acute neuroexcitation due to sodium channel modulation while subsequent recovery is feasible if an insect possesses sufficient metabolic capacity to detoxify the compound after knockdown; for the claim that the study demonstrates for the first time that the relationship between knockdown speed and mortality at the individual level varies significantly among insecticide classes; and for the mixture result, in which a synergistic combination of two named Type I compounds showed enhanced toxicity and the advent of the knockdown-mortality relationship. https://scijournals.onlinelibrary.wiley.com/doi/10.1002/ps.70998?af=R
3. Bibliographic record and abstract for the study cited immediately above, in a biomedical literature database. Source for the study's stated conclusion that knockdown speed should not be used as a proxy for lethality for Type I pyrethroids, highlighting class- and mixture-dependent dynamics between knockdown and mortality, and that the findings support regulatory and operational decisions considering knockdown and mortality as distinct performance endpoints, particularly when substantiating claims such as quick kill or kills on contact for pesticide registration; and for the keyword list indicating that computer vision was the observation method. https://pubmed.ncbi.nlm.nih.gov/42285910/
4. Influence of temperature on knockdown, toxicity, and resistance to pyrethroids in the house fly, Musca domestica. Journal article in a pesticide biochemistry and physiology title, published several decades ago and read as its abstract. Source for the study design examining knockdown, toxicity and resistance to four named compounds at 18, 25 and 32 degrees in a susceptible strain, a strain with a known knockdown resistance mechanism and a multiply resistant strain with unknown mechanisms; for the finding that penetration and recovery from knockdown occurred more rapidly at higher temperatures; for the finding that all four pyrethroids showed greater kill at 18 than at 32 degrees, with differences varying by compound and to a lesser extent by strain; and for the attribution of the negative temperature coefficient to rate of metabolism, excretion and redistribution together with reactivity at the site of action, with two compounds attributed to both causes and two likely attributed primarily to increasing metabolism, excretion and redistribution with increasing temperature. https://www.sciencedirect.com/science/article/abs/pii/0048357584900737
5. Mechanisms of pyrethroid insecticide-induced stimulation of calcium influx in neocortical neurons. Open-access journal article, read as extracts. Source for the statement that the action of pyrethroids on sodium channels is temperature-dependent and that sensitivity to pyrethroid exposure can be augmented by lowering temperature, citing earlier work; and for the authors' confirmation of a modest temperature dependence for deltamethrin-induced calcium influx in neocortical neurons, with lowering the temperature from 37 to 22 degrees producing a 2.6-fold increase in potency. https://pmc.ncbi.nlm.nih.gov/articles/PMC3014305/
6. Evidence for a separate mechanism of toxicity for the Type I and the Type II pyrethroid insecticides. Journal article in a neurotoxicology title, read as abstract and extracts. Source for the proposal, based on neurotoxicity data and effects on sodium, calcium and chloride ion channels, that several named compounds belong to one common mechanism group and several others to a second, with two named compounds occupying an intermediate position between them; for the historical account that pyrethroids were classified into two subclasses based on induction of either the T syndrome, whole body tremor, or the CS syndrome, choreoathetosis with salivation, following intravenous or oral administration to rats at near-lethal dose levels, with the T syndrome consisting of aggressive sparring, sensitivity to external stimuli, fine tremor progressing to whole body tremor and prostration, and elevation in core body temperature attributed to excessive muscular activity associated with tremor; for the statement that the transition between the two syndromes corresponds to a time constant of about 200 milliseconds in the frog and 10 milliseconds in the rat, and that compounds producing time constants in the transitional range tend to result in mixed-type clinical signs which may indicate simultaneous occurrence of both syndromes rather than a distinct third one; for the statement that research on knockdown resistance in insects and modelling of pyrethroid binding to the sodium channel lend support to the existence of unique binding sites for the two types; and for the note that pyrethroids act on isoforms of voltage-sensitive calcium channels contributing to neurotransmitter release, with evidence that action at sites other than the sodium channel may contribute to their effects in vivo. https://www.sciencedirect.com/science/article/abs/pii/S0161813X09001879
7. Retrospective account of work on the mechanism of the negative temperature coefficient of the nerve blocking action of a named pyrethroid, in a biochemistry journal, read as an extract. Source for the statement that pyrethroids without an alpha-cyano group and DDT analogues retain sodium channels in a modified open state only transiently, cause large depolarizing afterpotentials and evoke repetitive firing with minimal effect on the resting potential; for the finding that effects of the phenoxybenzyl pyrethroids were intermediate between the two extremes, suggesting that a continuous variation exists in the kinetics with which pyrethroids and DDT analogues modify sodium channels; for the explicit statement that it was not necessary to assume a second site of action to account for the variability observed; and for the note that the two classes were originally divided on effects on cercal sensory nerves recorded in vivo and in vitro and on symptomology produced in dosed cockroaches. https://www.sciencedirect.com/science/article/abs/pii/S0022356525292965