Even seasoned adventurers sometimes flinch at the mention of swarms. Yet even ordinary insects can form irritating (if nonlethal) swarms under the right conditions. Some trackers claim they can predict the conditions under which insect swarms form. For example, one tracker might insist it’s the change in barometric pressure before a storm that triggers swarming, while another might believe it’s a change in the prevailing winds. The potential causes are as numerous as the people who espouse them, and if folklore holds a definitive answer, it has yet to become common knowledge.
Extremely large swarms can devastate whole swaths of countryside, but the type of insect swarm most common to jungle travelers is the small, localized swarm often clouds of small, non-biting insects like gnats that insist on flying close to drink the humans’ sweat, crawling unpleasantly on eyeballs and up nostrils. These clouds obscure vision, create irritation, and can even transmit disease. A character on watch for such things can make a DC 25 Survival check to notice an insect swarm and change course to avoid the swarm.
Moving, living creatures attract the attention of insect swarms, especially if they smell strongly or are actively sweating. A group of adventurers that stumbles into a swarm finds itself pestered by the insects for 3d6 rounds or until the swarm disperses. Swarms disperse under several conditions, including the following: a gust of wind or stronger wind effect (whether naturally or magically created), a fire effect that covers at least half the swarm (including torches, provided there’s one for each square of the swarm), the submersion of all members of the party in water for 3 consecutive rounds, or a repel vermin spell that covers all members of the party for 3 consecutive rounds. Most swarms occupy a cube that measures 10 feet per side, though reports of larger swarms exist. A swarm can move up to 40 feet per round, squeeze through any space at least 5 feet wide, and occupy squares already occupied by other creatures, even other swarms.
Any living creature that begins its turn in a square occupied by a swarm must make a DC 13 Fortitude save or be sickened for 1 round. A swarm also has a 25% chance of carrying disease. If the swarm carries a disease, a character who fails his Fort save is sickened and must make an additional save or be infected with one of the following contact diseases:
All are contact diseases from Pathfinder Chronicles: Heart of the Jungle and the save DC varies by disease.
A swarm obscures vision, and any creatures within the swarm are considered dazzled for as long as they remain in it. Creatures within the swarm also have concealment (20% miss chance). Spellcasting or concentrating on spells within the area of a swarm requires a caster level check (DC 10 + spell level). Using skills that involve patience and concentration requires a DC 15 Will save.
Common irritating swarms include gnats, black flies, and mosquitoes. Flightless swarms, such as swarms of ants, spiders, and maggots, also use the rules presented here but occupy a square rather than a cube and do not impede vision or grant concealment. These swarms should not be confused with deadly swarms, which include monsters like wasps, spiders, and other dangerous insects and follow the normal monster rules for swarms.
A character can take certain precautions against non-deadly insect swarm effects. Covering all exposed skin (for example, by donning gloves, wrapping a scarf around one’s face, and so on) takes a full-round action and grants a +4 circumstance bonus on saving throws made to avoid being sickened or contracting a disease. Various salves made of bitter, nonmagical jungle herbs are available to travelers in major towns for the vastly inflated price of 10 gp a dose (though many of these turn out to be fake or ineffective). If a traveler applies a genuine dose of this salve, it causes all non-deadly swarms to avoid coming within 5 feet of him for at least 1 hour, removing all associated penalties for that character.
Pathfinder Chronicles: Heart of the Jungle. Copyright 2010, Paizo Publishing, LLC; Authors: Tim Hitchcock, Jason Nelson, Amber Scott, Chris Self, and Todd Stewart.