Swarm. The swarm can occupy another creature's space and vice versa, and the swarm can move through any opening large enough for a Tiny insect. The swarm can't regain hit points or gain temporary hit points.
Actions
Bites. Melee Weapon Attack: +3 to hit, reach 0 ft., one target in the swarm's space. Hit: 10 (4d4) piercing damage, or 5 (2d4) piercing damage if the swarm has half of its hit points or fewer.
How many swarms of insects for a fight?
A swarm of insects is worth 100 XP. Using the 2024 encounter budgets (SRD 5.2), this is how many swarms of insects fit each difficulty for a party of four characters of the same level. A dash means even one would be over the budget.
Party level
Low
Moderate
High
1st
2
3
4
2nd
4
6
8
3rd
6
9
12+
4th
10
12+
12+
Budgets add up every monster’s XP, so you can swap some for other creatures of the same total. Try other party sizes and mixes in the encounter calculator.
How the swarm of insects compares at CR 1/2
Against the 32 other challenge 1/2 monsters in the SRD 5.1, the swarm of insects has more hit points than 15 of them, which makes it a little frailer than most at its CR. See every CR 1/2 monster.
Statistic
Swarm of Insects
CR 1/2 average
Armor Class
12
12.4
Hit points
22
20
Best attack bonus
+3
+4
Swarm of Insects 2024 stat block
The 2024 Monster Manual revised the swarm of insects, and the SRD 5.2 carries the new stat block. What changed:
Armor Class: 12 → 11.
Hit points: 22 → 19.
Speed: 20 ft., climb 20 ft. → 20 ft., climb or fly 20 ft. (GM’s choice).
Spider Climb. If the swarm has a Climb Speed, the swarm can climb difficult surfaces, including along ceilings, without needing to make an ability check.
Swarm. The swarm can occupy another creature’s space and vice versa, and the swarm can move through any opening large enough for a Tiny insect. The swarm can’t regain Hit Points or gain Temporary Hit Points.
Actions
Bites. Melee Attack Roll: +3, reach 5 ft. Hit: 6 (2d4 + 1) Poison damage, or 3 (1d4 + 1) Poison damage if the swarm is Bloodied.
