from the nest by workers. 'refuse piles' or 'graveyards' are common features of ant colonies, and workers remove corpses (within the hour after death) to these piles after detecting death signatures in the cuticular hydrocarbon chemistry. corpse deposition is biased towards downward slopes, which saves the corpse-transporting worker energy as well as preventing any rain washing the corpses back into the colony - necrophoretic behaviours are distinct from ant responses to foreign inanimate objects as corpses are transported further and quicker. by bringing corpses out of the nest the ultraviolet radiation in sunlight can kill emerging fungal spores; atta transport corpses to special refuse chambers rather than into the external environment. temnothorax lichtensteini ants remove the corpses of dead sisters as above, but bury newly-dead foreign corpses inside the nest - whilst one or a few individuals 'decide' to transport or bury a corpse, up to 25 workers are then involved in the undertaking of one corpse. termites commonly bury and cannabalize corpses: when c. formosanus colonies are infected with m. anisopliae, necrophagy is common when the proportion of dead individuals in an area was low (15%), but as mortality increased then so did burying behaviour up to 75%–80% mortality above which carcasses were too numerous for workers to bury and secondary rounds of m. anisopliae infection was possible. termites do occasionally remove dead from the nest but this is uncommon (leaving the nest at all is rare); refuse chambers or piles/graveyards have not been observed. research on undertaking behaviours in bees has concentrated on the honeybee (apis mellifera): 1–2% of a colony are undertaker bees, specialized for corpse removal: they inspect corpses with their antennae before rapidly dropping them from the nest. waste material is removed continuously and deposited in refuse piles as above (or even by some atta ants into streams). the division of labour in acromyrmex echinatior leafcutter ants includes individuals who work almost exclusively in waste management: waste material (excreta, food refuse, etc.) frequently harbours escovopsis (a microfungus that is parasitic on the fungus that a. echinatior tends) as well as other parasites, so spatial separation of waste material from the fungal garden and wider nest environment is of paramount importance. this is achieved by depositing waste material on downhill and downwind piles or in special deep underground refuse chambers. distinct waste management workers also exist in atta cephalotes and atta colombica. the risk of waste-worker ants contaminating the fungal garden/nest is lowered by other ants attacking them if they try to enter the nest, whilst attacks are more frequent in species with internal refuse chambers (this also reinforces the division of labour). on the other hand, some species retain excreta and/or anal exudates within the nest to utilize it for antiparasite purposes: c. formosanus employs its faces as building material for the nest carton, the use of faecal material promotes the growth of actinomycetota with natural antimicrobial activity (e.g. streptomyces), combating fungal parasites like m. anisopliae. colony members of the buff-tailed bumblebee (bombus terrestris) defend themselves against the virulent crithidia bombi parasite by consuming beneficial gut bacteria from the faces of conspecific after eclosing.small hive beetles inside a bee colony workers of the cape honeybee (apis mellifera capensis) 'socially encapsulate' the parasitic small hive beetle (aethina tumida). a. tumida feeds on the brood, pollen and honey, but due to its robust exoskeletal armour and habit of remaining motionless in small gaps (with its head tucked turtle-like underneath its pronotum), honeybee workers find it difficult to decapitate and kill. instead, workers seal the small hive beetles in using 'bee glue' (propolis). construction of the 'propolis prisons' by some workers takes 1–4 days but is accompanied by other workers guarding the small hive beetle to prevent it escaping. guards have been observed remaining day and night for up to 57 days and attacking the small hive beetle if it tried to escape. some non-eusocial insects also sanitize their nests: the wood cockroach (cryptocercus punctulatus) commonly defecates within the nest (this species nests in decaying wood, which often has a high microbe density), and faeces have been found to have antifungal activity against m. anisopliae, possibly mediated by microbes. the galleries constructed within spruce trees by spruce beetles (dendroctonus rufipennis) are under threat from multiple species of fungus which reduce spruce beetle fitness. upon fungal invasion, adults begin secreting orally and analysis of these secretions has revealed bacteria with antifungal activity; faecal pellets are used to quarantine off fungally-infested sections of the gallery. a waste management strategy exists in some group living and subsocial species, such as the subsocial de geer's short-tailed cricket (anurogryllus muticus). 5–10 minutes after defecating and returning to her eggs, a. muticus females return to the fecal pellets and removes them out of the chamber — note no other items are removed from the chamber. upon discovering a carcass, subsocial n. vespilloides parents upregulate the antimicrobial activity of their anal exudates and smear them over the carcass - thus sanitizing the resource their brood will soon feast on. inhibiting intra-group transmission if a parasite has entered the nest and established itself, groups must now mount defences which inhibit the spread of parasites from infected to uninfected group members. the risk of infection for an uninfected individual is dependent on three factors: their susceptibility to the parasite, contact rate between infected and uninfected individuals and the infective ability (virulence) of the parasite. in eusocial insects, defences include: allogrooming, where individuals groom other conspecifics bodies, is an extremely common mechanism of social immunity in eusocial insects. when ants allogroom they rub legs and lick each other clean; any parasites found on the cuticle are stored in a special cavity in the foregut (the infrabuccal cavity, which is found on the ventral surface of the buccal cavity) - this prevents ingestion of the parasite by the groomer. the contents of the infrabuccal cavity are then killed by the chitnolytic activity of labial gland secretions before being expelled as a pellet with other debris to refuse piles in or out of the nest. upon exposure to m. anisopliae, self-grooming rates of the dampwood termite z. angusticollis remain constant whilst allogrooming increases by up to 53-fold; allogrooming here may not only remove fungal spores as the saliva applied concomitantly could reduce spore viability, similar to the antibacterial activity of vespula wasp larvae's saliva. some honeybee workers become specialized for near-continuous allogrooming. colony-level inhibitory strategies can also create 'organizational immunity'. for example, social insect workers tend to work initially at the centre of the nest, nursing the brood, and as they age adopt tasks closer and closer to the periphery, e.g., foraging. this compartmentalization, termed centrifugal polyethism, means that workers of the same age interact mainly with others of the same age, who are performing the same task in the same spatial compartment: thus if a new disease arises that is transmitted through physical worker-worker contact it is limited to one section of the colony. the spatial structuring of western honey bee colonies (apis mellifera) privileges young individuals-when colonies are afflicted with diseases that have a short infectious period (the time period during which infected individuals can transmit the disease to susceptible individuals), it is confined only to the older individuals closer to the outside. in the common eastern bumblebee (bombus impatiens), workers who feed larvae tend to remain near the centre of the nest even when not performing this activity, and the converse is true for workers who forage; 11–13% of workers remain in small zones a particular distance from the nest centre throughout their life. the demographic distribution of a colony can also can be utilized for antiparasite purposes: work on z. angusticollis has shown that not only are there differences to parasite susceptibility between instars but that the demographic constitution of a group significantly affects survivorship (mixed age groups do better than single-age groups). the effect of colony structuring on disease dynamics and social immunity is also analyzed theoretically using mathematical models. dying temnothorax unifasciatus workers voluntarily exclude themselves from the colony and die in solitude social exclusion of infected individuals can also prevent intra-group transmission. when dampwood termites (z. angusticollis) come into contact with high densities of entamopathogenic fungal spores, they perform a whole-body "vibratory motor display" which induce others who are not in direct contact with the spores to flee, increasing their distance from the infected individual. in the eastern subterranean termite (r. flavipes) infection with the same fungus also causes a vibratory alarm response; termites then aggregate around the infected individual and box it in, preventing it from moving to other areas of the colony; it is sometimes licked and bitten before subsequently being buried. individual temnothorax unifasciatus ants who are dying due to fungal infection, carbon dioxide poisoning or 'naturally' (of unknown cause in colonies which had not been experimentally manipulated) permanently leave the nest one to 50 hours before their death, altruistically ceasing all social interactions with nestmates and dying alone away from the colony. some apis mellifera workers are 'hygiene specialists'—they detect cells in the colony containing diseased or dead brood, uncap these cells and then remove the cell contents. the genetic homogeneity of insect colonies makes them theoretically susceptible to infection en masse; the high similarity of each group members genome means that each is susceptible (and resistant) to the same parasites, whilst experimental manipulation has demonstrated that genetically heterogenous colonies of b. terrestris have lower levels of parasite infection than homogeneous colonies. to increase genetic diversity, colonies can increase the number of queens and/or increase the number of mating partners a queen has— it is thought these social immune benefits may explain the seemingly costly polyandry found in social insect colonies. social hymenoptera also have exceptionally high rates of meiotic recombination when compared against a wide range of higher eukaryote taxa which further increases genetic diversity. ongoing theoretical and empirical work is seeking to tease out the scenarios in which these immune benefits of genetic heterogeneity can be negated due to concomitant costs, e.g., the increased intra-colony conflict and/or susceptibility to an increasing number of parasites which comes with increased genetic diversity. to combat heat-sensitive parasites, group members can elevate their temperature collectively—this defence is known as social fever and so far has only been found in honeybees (apis): upon challenge by chalk brood (ascosphaera apis), workers increase nest temperature preventatively—it is currently undetermined whether the cue for this action is due to the larvae communicating their infection to the workers or the workers detecting the parasite before symptoms develop. allogrooming exists in presocial insects—the european earwig (forficula auricularia) grooms its eggs to prevent mold growth and wood roach (cryptocercus) nymphs spend up to a fifth of their time grooming adults (nymphs also groom other nymphs but at a lower frequency, however allogrooming is not seen in adults)— but overall the role of parasite defence in presocial taxa's allogrooming behaviour is currently unresolved. nest abandonment is a last resort for a colony overwhelmed by an infection against which the defences listed above have not been effective—infected individuals can then be left deserted in the old nest or expelled from the group whilst the colony travels to a new nest. allogrooming in golden lion tamarins (leontopithecus rosalia) other taxa social immune systems have been observed across a wide range of taxonomic groups. allogrooming is found in many animals—for example primates frequently groom others, a behaviour which likely evolved for its hygienic function but has now been co-opted for its additional role in social bonding. allogrooming in the common vampire bat (desmodus rotundus) is associated with the regurgitation of food and may allow other bats to identify which individuals are capable of supplying them with food; the allogrooming behaviours of horses and birds have also been studied. a range of sometimes elaborate cleaning symbioses also exist between many different species, especially in marine fish with their cleaning stations. corsican blue tits (parus caeruleus) prophylactically line their nest with aromatic plants (such as achillea ligustica, helichrysum italicum and lavandula stoechas) to ward off mosquitoes and other blood-sucking ornithophillous (bird-targeting) insects. according to richard dawkins's concept of the extended phenotype, human healthcare activities, such as vaccination (depicted here) could be seen as social immunity after the broader definition of social immunity by cotter and kilner, numerous examples of social immune behaviours