Five Volatiles and a Histamine: The Chemical Ecology of Bed Bug Aggregation and Why Apartments Share Infestations

1. Introduction: behaviour explains the pattern

The preceding article in this journal argued that most rodent control failure is behavioural rather than chemical, and that a literature going back to the 1950s explains it. The same case can be made for bed bugs, with one difference: the relevant chemistry was not fully resolved until 2015.

Bed bugs are obligate blood feeders living in close proximity to humans, and since their global resurgence in the early 2000s they have become one of the most challenging insects to control indoors.³

1.1 Why the chemical ecology took so long

Despite intense research on bed bug aggregation behaviour and the aggregation pheromone, which could be used as a chemical lure, the complete composition of that pheromone proved elusive for decades.¹

Practitioners have known that bed bugs aggregate in harbourage since the species was first a problem. What the identification supplied was why, and the why turns out to be operationally useful.

2. The pheromone, identified in 2015

The resolution came from work published in Angewandte Chemie.

The bed bug aggregation pheromone comprises five volatile components, namely dimethyl disulfide, dimethyl trisulfide, (E)-2-hexenal, (E)-2-octenal and 2-hexanone, which attract bed bugs to safe shelters, and one less volatile component, histamine, which causes their arrestment upon contact.¹

2.1 The practical demonstration

In infested premises, a blend of all six components is highly effective at luring bed bugs into traps. The trapping of juvenile and adult bed bugs, with or without recent blood meals, provides strong evidence that this pheromone bait could become an effective and inexpensive tool for detection and potentially for control.¹

The detail that matters there is the breadth of response. The blend caught juveniles and adults, fed and unfed. A lure that only worked on hungry adults would miss most of a population.

2.2 Where the pheromone comes from

Volatile aggregation pheromone components are derived from sternal glands and faeces.³ The six compounds are present in both the faecal material and the bed bug itself.²

This is why harbourage marked with faecal spotting is self-reinforcing. The deposit is not merely evidence of past occupation; it is an active signal recruiting further occupation.

3. Attraction and arrestment are separate systems

The single most useful conceptual point in this literature is that getting an insect to a place and getting it to stay there are driven by different compounds.

Volatile aggregation pheromone components attract bed bugs to shelters, whereas arrestment is driven by histamine in bed bug faeces.³ It is noteworthy that attraction and arrestment are driven by two different sets of compounds in shelter-seeking bed bugs.³

3.1 Why the separation makes sense

Volatiles travel and therefore work at distance, but they cannot confirm that a specific crevice is suitable. A non-volatile contact cue cannot advertise at range, but it can confirm on arrival that conspecifics have been here and survived.

Two systems, two ranges, two jobs. A lure exploiting only one of them will underperform, which is the argument for the six-component blend rather than the volatiles alone.

3.2 The consequence for control

It also means an intervention can act on either. Something that interferes with arrestment without repelling would leave insects mobile and unsettled, which §7 shows human skin already does naturally.

4. Histamine

The arrestment component deserves separate treatment because its production has an unexpected feature.

The faeces of C. lectularius contain a large amount of histamine, which is one of the six known aggregation pheromone components.¹

4.1 It is manufactured, not merely passed through

Histamine is partially synthesised from histidine acquired from blood meals, but this constitutes only a fraction of the histamine bed bugs produce, which suggests histamine is primarily synthesised de novo.²

An insect that manufactures a compound rather than excreting a dietary by-product is investing metabolically in it. That is the signature of a signal rather than a waste product.

4.2 The indoor environment

Bed bugs clearly contribute histamine to the indoor environment.² Infestation is associated with contamination of the indoor environment with histamine and other compounds.³

This connects to the health literature examined elsewhere in this journal. The cockroach allergen article established that a pest can impose a measurable exposure independent of its bites or its presence, and histamine deposition is the bed bug analogue. We have not reviewed the clinical literature on domestic histamine exposure and do not extend the claim.

4.3 Why it persists

Histamine is a stable, non-volatile deposit. Unlike the volatiles, it does not dissipate when the insects leave, which means a treated and emptied harbourage retains its arrestment signal.

That has a direct implication for post-treatment recolonisation: the crevice that held the original aggregation remains chemically marked as a good place to stop.

5. Cast skins as a persistent signal

A second source of arrestment chemistry is the material every developing bed bug leaves behind.

Extracts of the exuviae, meaning cast skins, of nymphal bed bugs were analysed for volatile compounds that might contribute to arrestment of adults. Four volatile aldehydes, (E)-2-hexenal, 4-oxo-(E)-2-hexenal, (E)-2-octenal and 4-oxo-(E)-2-octenal, were consistently detected in the headspace of freshly shed exuviae regardless of the developmental stage from which the exuviae were obtained.²

5.1 Why this matters for inspection

Two of those four aldehydes, (E)-2-hexenal and (E)-2-octenal, are among the five volatile aggregation pheromone components identified in 2015.¹

So cast skins are not inert debris. They emit components of the aggregation signal, which means an inspector finding exuviae has found something that is actively recruiting, not merely a historical record.

5.2 The cleaning implication

Physical removal of faecal deposits and cast skins from harbourage is usually presented as cosmetic or as removing evidence. On this chemistry it is removal of the aggregation signal itself.

We are not aware of a study measuring whether harbourage cleaning reduces recolonisation rate, and we would like to see one. The mechanism is there.

6. The tactile basis of arrestment

The sensory work establishes how close the insect has to get before the arrestment signal operates.

Aggregation by bed bugs is a result of arrestment mediated by direct, close-range contact between sensilla on the pedicel and stained experimental discs.⁴

The pedicel is the second antennal segment. Arrestment therefore requires the insect to physically touch the marked surface with its antenna.

6.1 The range consequence

This sharply limits the distance over which the strongest aggregation cue operates. A crevice heavily marked with faeces exerts no arrestment influence on an insect two centimetres away; it exerts it on an insect touching it.

Combined with §3, the picture is of volatiles doing coarse navigation over a room and contact chemistry doing final selection within a crevice.

6.2 Why aggregations are tight

Contact-mediated arrestment explains the characteristic density of bed bug harbourage. Each individual that stops adds deposit, which arrests the next individual that touches it. The aggregation is self-assembling through a purely local rule.

7. Why they do not live on you

An obvious question about an obligate blood feeder, with a chemically specific answer.

Bed bugs are nocturnal and use multiple sensory cues to detect and orient towards their human hosts. After feeding, usually on a sleeping human, they return to a shelter on or around the sleeping surface, but not directly on the host.³

7.1 The hypothesis and the finding

Researchers hypothesised that although human skin odours attract hungry bed bugs, human skin compounds may also prevent arrestment on hosts. The finding was that human skin triglycerides prevent bed bug arrestment.³

The authors are careful about the mechanism. Bed bugs moved freely between both shelters in the assay, suggesting triglycerides do not interfere with attraction to the shelter and are likely not repellent, but rather prevent bed bugs from arresting on it.³

7.2 Why this is adaptive

A parasite that settled on a mobile, grooming host would be removed. One that feeds and withdraws to a crevice within a couple of metres gets the meal without the exposure.

It also explains the distribution an inspector finds: harbourage concentrated on and immediately around the bed rather than on the occupant or their clothing, which is a diagnostic pattern rather than an accident.

8. Who aggregates and who does not

Aggregation is not uniform across the population, and the variation follows the species' unusual reproductive biology.

The propensity of adult females to aggregate is comparatively lower than that of adult males and nymphs.⁵

When mated and unmated females were compared for aggregation activity on shelters treated with putative volatile aggregation pheromone components, only unmated females were attracted.⁵

8.1 The likely explanation

Bed bugs reproduce by traumatic insemination, in which the male pierces the female's abdominal wall. Mating carries a direct physical cost to the female, and aggregations are where males are.

A mated female avoiding pheromone-marked shelters is avoiding further mating, which is consistent with the observed pattern. We offer that interpretation as reasoning, since the sources report the behavioural result rather than its cause.

8.2 The operational consequence

A pheromone-baited monitor is therefore biased. It will be most attractive to nymphs, adult males and unmated females, and least attractive to mated females, which are the individuals founding new aggregations.

That is a meaningful limitation on pheromone-based detection and it is not, in our reading, widely acknowledged in the product literature.

9. The alarm pheromone

Bed bugs possess a second signalling system with the opposite function, and it has a strange evolutionary origin.

Nymphs produce an anti-aphrodisiac defence against conspecific males.⁶ Mounting males treat the alarm signal as a major sex identification cue, which suggests that male bed bugs use alarm pheromone communication to avoid homosexual harassment and mounting.⁴

9.1 Why traumatic insemination produces this

Because insemination physically injures the recipient, being mounted is costly regardless of sex. Nymphs and males both benefit from a signal that terminates a mounting attempt, and the alarm pheromone serves that function.

9.2 The disturbance response

The same chemistry operates as a general alarm. Alarm pheromone emission elicits a movement response in nearby recipients,⁶ which is the basis of §10.

10. Heat exposure triggers alarm

One recent finding connects directly to the thermal treatment article published elsewhere in this journal, and it complicates the picture there.

Lethal and sub-lethal heat exposure of bed bugs causes alarm pheromone emission and elicits a movement response in nearby recipients.⁶

10.1 Why this matters for thermal work

The thermal article set out that bed bug mortality is a function of time and temperature, and that the operational challenge is achieving lethal exposure throughout a structure including within harbourage and voids.

This finding adds a behavioural dimension. Insects experiencing sub-lethal heating at the margins of a treated zone are not merely surviving; they are signalling, and nearby individuals are responding by moving.

10.2 What follows practically

It reinforces the argument already made in the thermal article that the binding constraint is uniformity of exposure rather than peak temperature, and it supplies an additional mechanism for why partial treatments underperform rather than simply reducing numbers proportionally.

We are not aware of work quantifying how far the movement response extends or whether it produces measurable escape from treatment zones in the field, and that seems a worthwhile question.

11. Carbon dioxide as the master cue

Turning from shelter-seeking to host-seeking, one cue dominates.

Carbon dioxide is a recognised kairomone acting alone or in synergy with other compounds on the orientation of haematophagous insects toward their host, and is considered the stimulus with the greatest influence on host-seeking behaviour in bed bugs.⁷

11.1 The substitution test

Carbon dioxide would be the cue most representative of host presence, since replacing the host with a carbon dioxide source generates rapid aggregation of C. lectularius toward the artificial source.⁷

That is a strong result. The insects orient to the gas in the absence of any actual animal, which establishes carbon dioxide as sufficient rather than merely correlated.

11.2 Activity effects

Bed bugs show activity peaks during the night, and activity is increased by elevated levels of carbon dioxide.⁸

So the gas both attracts and arouses. A sleeping occupant is simultaneously a beacon and a stimulant.

12. The switch from local to long range search

The most behaviourally interesting host-seeking result concerns a change in search mode.

In environments lacking human breath, bed bugs show random, stop-start host-seeking movement. Those exposed to a human breath stimulus demonstrate long-range host-seeking behaviour directed toward the stimulus.¹⁰

When exposed to breath from a human host, bed bugs altered their host-seeking behaviour from localised to long range searching, indicated by an increase in net displacement and mean distance from the harbourage.¹¹

12.1 What a mode switch means

This is not a gradient-following response where the insect simply walks up a concentration slope. It is a change of strategy: absent a cue the animal searches locally and conservatively, and on detecting a cue it commits to travelling.

Bed bugs have been reported to travel distances of more than six metres to reach a host, purportedly under the influence of carbon dioxide containing breath stimuli.¹⁰

12.2 The connection to the corridor

This mode switch supports previous findings that bed bugs have been found moving from infested apartments to neighbouring apartments via the hallways.¹¹

An insect that only searched locally would not do that. One that commits to long-range directed movement on detecting a host cue plausibly would, and §16 shows it happens.

13. The energy cost of searching

The literature frames the trade-off explicitly, and it explains the conservatism of the default mode.

In obligatory haematophagous insects like the bed bug, searching may be a double-edged sword, increasing the chance of locating a host but also depleting limited energy stores.¹¹

Resource specific cues would therefore only stimulate localised searching in cases where it would be advantageous to thoroughly explore the immediate area for a host. This is an indication of how a specific host cue fits into the entire host-seeking pathway of the insect.¹¹

13.1 Why this matters for vacant units

An insect with finite reserves and no host is in a bind: searching costs energy it cannot replace. The rational strategy is to conserve and wait, which is exactly what the survival data in §19 show.

13.2 The treatment implication

A vacated unit does not starve out a population quickly, and the energy economics explain why. The animals are not burning reserves searching; they are sitting still.

14. The engineered lure

Understanding of these cues has been assembled into working devices, and the composition is published.

A trap designed for the bed bug baited with carbon dioxide at 50 to 400 millilitres per minute, heat at 37.2 to 42.2 degrees Celsius, and a chemical lure comprising 33 micrograms propionic acid, 0.33 micrograms butyric acid, 0.33 micrograms valeric acid, 100 micrograms octenol and 100 micrograms l-lactic acid impregnated into a gel, caught significantly more bed bugs than controls in laboratory experiments.⁴

14.1 Reading the recipe

The three elements map onto the sequence in §11. Carbon dioxide provides long-range orientation, heat provides close-range confirmation at approximately host body temperature, and the carboxylic acids, octenol and lactic acid supply the skin volatile profile.

The quantities are also informative. Propionic acid at 33 micrograms is a hundred times the butyric and valeric acid quantities, which indicates the blend is a specific ratio rather than an assortment.

14.2 Performance

In environmental chambers of 3.1 by 1.8 metres, a pitfall trap baited with carbon dioxide, heat and chemical lure trapped 57.3 per cent of the bed bugs overnight.⁹

Fifty seven per cent of a population in a single night is a substantial capture rate, though a chamber is not a furnished bedroom.

15. Traps against visual inspection

The field comparison is the result that should change practice.

The pitfall trap was tested in four bed bug infested apartments to determine efficacy in detecting light infestations. Visual inspections found an average of 12.0 bed bugs per apartment, and the bed bugs found by visual inspection were hand-removed during the inspections. A pitfall trap baited with carbon dioxide and chemical lure was subsequently placed in each apartment, with an average of 15.0 bed bugs collected per trap by the next morning.⁹

15.1 Why the removal detail matters

The visually detected insects were taken out before the traps were set. The traps then caught more than the inspection had found, from what remained.

A thorough visual inspection therefore located fewer than half the insects that a single baited trap collected overnight from the remainder. That is a substantial indictment of inspection as a sole detection method, and it aligns with the canine and monitor accuracy findings reviewed elsewhere in this journal.

15.2 The authors' conclusion

Baited pitfall traps are potentially effective tools for evaluating bed bug control programmes and detecting early bed bug infestations.⁹

Note both halves. Detection of early infestations, and evaluation of control programmes, which is the accountability function the remote monitoring article identified as the strongest argument for instrumentation.

16. Movement within and between apartments

The field movement study is the most consequential work for multi-unit housing.

Researchers conducted mark-release-recapture in occupied apartments. Extensive movement of marked bed bugs within and between apartments occurred regardless of the number of bed bugs released or presence or absence of a host. Comparison of marked and unmarked distributions confirmed that the extensive activity observed was not an artefact of the technique.¹²

16.1 The neighbouring unit finding

Marked bed bugs were recovered in apartments neighbouring five of six mark-release-recapture apartments. Their dispersal rates at 14 or 15 days were 0.0 to 5.0 per cent.¹²

16.2 The population sizes involved

The estimated number of bed bugs per apartment in the six study apartments was 2,433 to 14,291 at four to seven days after release.¹²

A dispersal rate of five per cent sounds modest until it is applied to a population of fourteen thousand. It is also worth noting how large established infestations can be, against a public perception formed by finding a handful of insects.

16.3 Speed

Under laboratory conditions bed bugs can travel up to 4.9 metres in five minutes, and it has been suggested they can travel greater distances during the night when they are active for hours at a time.¹²

17. Dispersal is not simply density driven

A conflict in the literature that has practical consequences.

Earlier work concluded that bed bug aggregations were rarely located more than 2.3 metres away from where the host slept, particularly in populations of fewer than 100 bed bugs, and that population density within harbourages seems to be the main driving force for dispersal.¹²

17.1 The contrary field result

In the mark-release-recapture study there was no relationship between the active dispersal rate of marked bed bugs to neighbouring apartments and the number of marked bed bugs released. These results suggest that infestation level alone is not responsible for dispersal.¹²

17.2 What else might drive it

The authors suggest that factors such as the amount of clutter and resident behaviour may also have affected dispersal, while noting their sample size was not large enough to analyse these relationships.¹²

17.3 Why this matters for triage

If dispersal scaled with population, a programme could prioritise heavily infested units and reasonably expect to contain spread. On this evidence it cannot.

A lightly infested unit may be exporting insects at a similar rate to a heavily infested one, which supports building-wide rather than severity-ranked intervention.

18. Which individuals leave

Dispersal propensity varies substantially by stage and condition, and the pattern is consistent across studies.

Laboratory work on aggregation behaviour suggested that first instar nymphs were the least likely developmental stage to disperse, and that recently fed adult females were the most likely to move away from aggregations.¹²

A separate study on the closely related tropical bed bug, Cimex hemipterus, concluded that distance travelled varied significantly based upon developmental stage, adult sex and feeding status, and similarly found that early instars were least likely to disperse while recently fed females were most likely.¹²

18.1 The founding individual

A recently fed adult female is precisely the individual capable of establishing a new infestation alone, since she carries both a blood meal and, in this species, stored sperm.

The stage most likely to leave is therefore the stage best equipped to found a population elsewhere. That is an unfavourable combination for containment.

18.2 The link to §8

Recall that mated females are not attracted to pheromone-treated shelters.⁵ The same individuals that disperse most readily are the ones least responsive to the aggregation signal.

A pheromone monitor is therefore weakest at detecting exactly the individuals whose movement matters most for spread. We regard that as the most important limitation of pheromone-based detection and it follows from combining two findings that are usually discussed separately.

19. Survival without a host

The persistence data determine how long a vacated unit stays infested.

Longevity of bed bugs in the absence of a host was recorded in a vacant apartment. Marked large nymphs of the third to fifth instar, adult females, and adult males continued to be recovered up to 57, 113 and 134 days after host absence respectively.¹²

19.1 What these numbers are and are not

These are durations over which marked individuals were still being recovered, which is a floor rather than a maximum. Recovery ended when the study ended.

They are also field conditions in an actual vacant apartment rather than controlled starvation trials, which makes them more directly applicable to a building manager's decision.

19.2 The practical reading

Adult males recoverable more than four months after the occupant left means that holding a unit vacant is not a control strategy on any timescale a landlord would accept.

It also means a unit re-let after a month is being re-let into a live infestation, and the new tenant's arrival supplies precisely the carbon dioxide cue of §11 that ends the waiting.

20. Passive dispersal

Active movement is only one route between units.

Bed bugs aggregate on dirty laundry, which constitutes a mechanism for passive dispersal.¹³

20.1 Why laundry specifically

Worn clothing carries human skin volatiles, which §11 and §14 establish as attractive to host-seeking bed bugs. A pile of worn clothing is therefore a host-scented object that does not move or groom.

The mechanism explains a transmission route that residents have direct control over, and it is one of the few in this article where advice to an occupant is both simple and evidence-based: worn clothing in a sealed container rather than an open pile, particularly when travelling or when a building has known infestation.

20.2 The shared laundry problem

In a multi-unit building with communal laundry, this mechanism connects units that have no physical adjacency at all. We have found no study quantifying that specific route and think it merits one.

21. What this means for monitoring

Pulling the detection findings together.

Baited traps outperform visual inspection. A single overnight baited trap collected more insects than a thorough inspection had found and removed.⁹

Use all three cue types where possible. Carbon dioxide, heat and chemical lure correspond to distinct stages of the orientation pathway.⁴⁹

Pheromone lures catch a biased sample. Nymphs, adult males and unmated females respond; mated females do not.⁵

Monitor neighbours, not just the reported unit. Marked insects reached neighbouring apartments in five of six cases.¹²

Faecal spotting and cast skins are active signals. Their presence indicates current recruitment chemistry, not merely past occupancy.¹²

22. What this means for treatment

Remove the arrestment deposit. Histamine is non-volatile and persists after the insects are gone,² and cast skins emit aggregation volatiles.² Physical cleaning of harbourage removes signal as well as debris.

Expect sub-lethal heat margins to push insects outward. Alarm pheromone emission under sub-lethal heat produces a movement response in nearby individuals.⁶

Do not rely on vacancy. Adult males were recovered 134 days after host removal.¹²

Expect the bed and its immediate surround to hold most of the population. Aggregations are rarely more than 2.3 metres from where the host sleeps in smaller infestations,¹² and skin triglycerides keep them off the occupant themselves.³

Treat clutter as a variable. The dispersal authors identify clutter and resident behaviour as plausible influences they could not test.¹²

23. What this means for multi-unit programmes

The building-scope argument this journal has made repeatedly now has direct empirical support for bed bugs specifically.

Unit-scoped treatment is contradicted by the movement data. Marked insects reached neighbouring units in five of six cases within about two weeks.¹²

Severity-based triage is contradicted by the dispersal data. There was no relationship between dispersal rate and population size, so infestation level alone does not predict export.¹²

Corridors are a route. Movement between apartments via hallways is reported.¹¹

Occupancy changes are high-risk moments. A new tenant supplies the carbon dioxide cue⁷ to a population that may have been waiting for months.¹²

Shared laundry deserves attention. Dirty laundry is an identified passive dispersal mechanism.¹³

24. Limitations and open questions

The movement study is small. Six mark-release-recapture apartments, with the authors themselves noting insufficient sample size to analyse clutter and resident behaviour relationships.¹²

Much of the behavioural work is laboratory based. The aggregation, arrestment and triglyceride findings come from arena and shelter assays.³⁴ The trap performance figure of 57.3 per cent was measured in environmental chambers.⁹

The trap and inspection comparison rests on four apartments. Averages of 12.0 and 15.0 with substantial standard errors.⁹ The direction is clear; the magnitude should not be over-read.

The two dispersal findings genuinely conflict. Set out in §17 rather than resolved. Density-driven and density-independent dispersal are both reported.¹²

Several interpretations are ours. The traumatic insemination explanation for mated female behaviour in §8.1, the combination of §8 and §18 into a pheromone monitoring limitation in §18.2, and the laundry reasoning in §20.1 are our inferences from reported findings rather than reported conclusions.

The heat and alarm finding is recent and not yet field-tested. We have found no work measuring whether the movement response produces escape from treatment zones in practice.⁶

No Canadian data. As with every behavioural question raised in this journal, we have found no Manitoba or Canadian work on bed bug movement between units in local housing stock.

25. Conclusion

The bed bug aggregation pheromone was fully identified only in 2015 and comprises five volatile components that attract toward shelters plus histamine, which causes arrestment on contact.¹ Attraction and arrestment are separate systems driven by different compounds,³ arrestment requires physical contact between antennal sensilla and the marked surface,⁴ and histamine is manufactured rather than excreted.²

That separation explains the distribution an inspector actually finds. Human skin odours attract hungry bed bugs while human skin triglycerides prevent them arresting, so they shelter on and around the sleeping surface and not on the person.³

For host-seeking, carbon dioxide is the dominant cue, sufficient on its own to produce rapid aggregation toward an artificial source,⁷ and human breath switches searching from localised to long range with increased net displacement from the harbourage.¹¹ That mode switch is what makes corridor movement between apartments plausible, and a mark-release-recapture study found marked insects in units neighbouring five of six release apartments.¹²

Two findings should change how multi-unit programmes are specified. Dispersal showed no relationship to population size, so infestation severity does not predict export.¹² And the stage most likely to leave an aggregation, the recently fed adult female,¹² is also the stage not attracted to pheromone-marked shelters,⁵ which means our best chemical monitor is weakest against the individuals that matter most for spread.

Adult males were still being recovered 134 days after the host left.¹² A single baited trap overnight collected more insects than a thorough visual inspection had already found and removed.⁹ Between those two numbers sits most of what is wrong with how this pest is managed: we look for it badly, and then we wait for it to go away.

References

1. Gries, R. et al. (2015). Bed Bug Aggregation Pheromone Finally Identified. Angewandte Chemie, 54, 1135–1138. Source for the identification of the aggregation pheromone as five volatile components, dimethyl disulfide, dimethyl trisulfide, (E)-2-hexenal, (E)-2-octenal and 2-hexanone, which attract bed bugs to safe shelters, together with the less volatile histamine which causes arrestment upon contact; for the effectiveness of the six-component blend at luring juvenile and adult bed bugs with or without recent blood meals into traps in infested premises; for the long-standing difficulty in resolving the pheromone's composition; and for the large quantity of histamine in bed bug faeces. https://www.researchgate.net/publication/282475751_Bed_Bug_Aggregation_Pheromone_Finally_Identified
2. Siljander, E., Gries, R., Khaskin, G. & Gries, G. Chemically Mediated Arrestment of the Bed Bug, Cimex lectularius, by Volatiles Associated with Exuviae of Conspecifics, together with associated work on histamine synthesis (Gries et al. 2018) and environmental contamination (DeVries et al.). Source for the four volatile aldehydes (E)-2-hexenal, 4-oxo-(E)-2-hexenal, (E)-2-octenal and 4-oxo-(E)-2-octenal consistently detected in the headspace of freshly shed exuviae regardless of developmental stage; for the presence of the six pheromone components in both faecal material and the bed bug itself; for histamine being only partially derived from blood meal histidine and primarily synthesised de novo; and for bed bugs contributing histamine to the indoor environment. https://www.researchgate.net/publication/282475751_Bed_Bug_Aggregation_Pheromone_Finally_Identified
3. Human skin triglycerides prevent bed bug (Cimex lectularius L.) arrestment. PMC. Source for bed bugs as obligate haematophagous pests and their status since the early 2000s resurgence; the association with allergic reactions, psychological distress and indoor contamination with histamine; the observation that bed bugs return after feeding to a shelter on or around the sleeping surface but not directly on the host; the hypothesis and finding that human skin triglycerides prevent arrestment while skin odours attract host-seeking stages; the observation that triglycerides do not interfere with attraction to shelters and are likely not repellent; and the statement that attraction and arrestment are driven by two different sets of compounds, with volatile pheromone components derived from sternal glands and faeces while arrestment is driven by histamine. https://pmc.ncbi.nlm.nih.gov/articles/PMC8654864/
4. Cimex lectularius overview. ScienceDirect Topics, citing Olson, J.F., Moon, R.D. & Kells, S.A. (2009), Off-host aggregation behavior and sensory basis of arrestment by Cimex lectularius, Journal of Insect Physiology, 55, 580–587, and Anderson, J.F. et al. (2009). Source for arrestment being mediated by direct close-range contact between sensilla on the pedicel and stained experimental discs; for male use of alarm pheromone communication to avoid homosexual harassment and mounting with the alarm signal as a major sex identification cue; and for the trap baited with carbon dioxide at 50 to 400 millilitres per minute, heat at 37.2 to 42.2 degrees Celsius and a chemical lure of 33 micrograms propionic acid, 0.33 micrograms butyric acid, 0.33 micrograms valeric acid, 100 micrograms octenol and 100 micrograms l-lactic acid impregnated in gel. https://www.sciencedirect.com/topics/immunology-and-microbiology/cimex-lectularius
5. Semiochemicals of the common bed bug, Cimex lectularius L. (Hemiptera: Cimicidae), and their potential for use in monitoring and control. Source for the comparatively lower propensity of adult females to aggregate relative to adult males and nymphs, and for the finding that when mated and unmated females were compared on shelters treated with putative volatile aggregation pheromone components, only unmated females were attracted. https://www.researchgate.net/publication/291985504_Semiochemicals_of_the_common_bed_bug_Cimex_lectularius_L_Hemiptera_Cimicidae_and_their_potential_for_use_in_monitoring_and_control
6. Lethal and sublethal heat-exposure of bed bugs (Cimex lectularius L.) causes alarm pheromone emission and elicits a movement response in nearby recipients. Scientific Reports (2024). doi:10.1038/s41598-024-57925-y. Source for the finding that both lethal and sub-lethal heat exposure triggers alarm pheromone emission producing a movement response in nearby individuals, and citing Harraca, V., Ryne, C. & Ignell, R. (2010), Nymphs of the common bed bug produce anti-aphrodisiac defence against conspecific males, BMC Biology, 8. https://www.nature.com/articles/s41598-024-57925-y
7. Legrand, P., Verheggen, F., Haubruge, E. & Francis, F. Host-seeking behaviour in the bed bug (Cimex lectularius) and applications in integrated pest management, a review. Biotechnologie, Agronomie, Societe et Environnement, 20, 195–202. Source for carbon dioxide as a recognised kairomone acting alone or in synergy on orientation of haematophagous insects toward hosts, its status as the stimulus with the greatest influence on bed bug host-seeking behaviour citing Anderson et al. 2009, Wang et al. 2009 and Aak et al. 2014, and the finding that replacing a host with a carbon dioxide source generates rapid aggregation toward the artificial source. https://www.researchgate.net/publication/26269706_A_carbon_dioxide_heat_and_chemical_lure_trap_for_the_bedbug_Cimex_lectularius
8. Two compounds in bed bug faeces are sufficient to elicit off-host aggregation by bed bugs, Cimex lectularius, together with associated work on bed bug activity and biopesticide transfer. Source for the statement that after feeding bed bugs aggregate in cracks and crevices near a host with aggregation and arrestment mediated by tactile and chemical cues, and for the finding that bed bugs show activity peaks during the night with activity increased by elevated levels of carbon dioxide. https://www.researchgate.net/publication/301203062_Two_compounds_in_bed_bug_feces_are_sufficient_to_elicit_off-host_aggregation_by_bed_bugs_Cimex_lectularius
9. Bed bug (Heteroptera: Cimicidae) attraction to pitfall traps baited with carbon dioxide, heat, and chemical lure. PubMed. Source for the environmental chamber result in which a pitfall trap baited with carbon dioxide, heat and chemical lure trapped 57.3 plus or minus 6.4 per cent of bed bugs overnight in 3.1 by 1.8 metre chambers; for the field test in four infested apartments where visual inspections found an average of 12.0 plus or minus 5.4 bed bugs per apartment which were hand-removed, after which a baited pitfall trap collected an average of 15.0 plus or minus 6.4 bed bugs per trap by the next morning; and for the conclusion that baited pitfall traps are potentially effective for evaluating control programmes and detecting early infestations. https://pubmed.ncbi.nlm.nih.gov/19736771/
10. Smelly Hangups for Mosquitoes and Bedbugs. Nature Scitable. Source for the summary that bed bugs show random, stop-start host-seeking movement in environments lacking human breath whereas those exposed to a human breath stimulus demonstrate long-range host-seeking directed toward the stimulus, and for the report that bed bugs travel distances of more than six metres to reach a host under the influence of carbon dioxide containing breath stimuli. https://www.nature.com/scitable/blog/student-voices/smelly_hangups_for_mosquitoes_and/
11. Reis, M.D. & Miller, D.M. (2011). Host searching and aggregation activity of recently fed and unfed bed bugs (Cimex lectularius L.). Insects, 2, 22 and 185–194. doi:10.3390/insects2010022. Source for the finding that exposure to human breath altered host-seeking behaviour from localised to long range searching as indicated by increased net displacement and mean distance from the harbourage; for the characterisation of searching in obligatory haematophagous insects as a double-edged sword increasing the chance of locating a host while depleting limited energy stores; for the reasoning that resource specific cues would stimulate localised searching only where thorough exploration of the immediate area is advantageous; and for support of previous findings that bed bugs move from infested apartments to neighbouring apartments via hallways. https://doi.org/10.3390/insects2010022
12. Mark-Release-Recapture Reveals Extensive Movement of Bed Bugs (Cimex lectularius L.) within and between Apartments. PLOS ONE. doi:10.1371/journal.pone.0136462. Source for extensive movement within and between apartments regardless of number released or host presence; recovery of marked bed bugs in apartments neighbouring five of six study apartments with dispersal rates at 14 to 15 days of 0.0 to 5.0 per cent; estimated populations of 2,433 to 14,291 per apartment at four to seven days after release; longevity in a vacant apartment with large nymphs, adult females and adult males recovered up to 57, 113 and 134 days after host absence; the absence of any relationship between dispersal rate and number released indicating infestation level alone is not responsible for dispersal; the suggestion of clutter and resident behaviour as untested influences; laboratory travel of up to 4.9 metres in five minutes; and citing Naylor on aggregations rarely more than 2.3 metres from where the host slept with density as the main driving force, plus Pfiester et al. and How and Lee on first instars being least likely and recently fed females most likely to disperse. https://journals.plos.org/plosone/article?id=10.1371%2Fjournal.pone.0136462
13. Bed bug aggregation on dirty laundry: a mechanism for passive dispersal. Scientific Reports. doi:10.1038/s41598-017-11850-5. Source for the identification of aggregation on soiled clothing as a passive dispersal mechanism. https://www.nature.com/articles/s41598-017-11850-5