Scute Swarm

Landfall — Whenever a land enters the battlefield under your control, create a 1/1 green Insect creature token. If you control six or more lands, create a token that's a copy of Scute Swarm instead.

Mazirek, Kraul Death Priest

Flying
Whenever a player sacrifices another permanent, put a +1/+1 counter on each creature you control.

Grist, the Hunger Tide

As long as Grist, the Hunger Tide isn't on the battlefield, it's a 1/1 Insect creature in addition to its other types.
+1: Create a 1/1 black and green Insect creature token, then mill a card. If an Insect card was milled this way, put a loyalty counter on Grist and repeat this process.
−2: You may sacrifice a creature. When you do, destroy target creature or planeswalker.
−5: Each opponent loses life equal to the number of creature cards in your graveyard.

Hornet Queen

Flying, deathtouch
When Hornet Queen enters the battlefield, create four 1/1 green Insect creature tokens with flying and deathtouch.

Amzu, Swarm's Hunger

Flying, menace
Other Insects you control have menace.
Whenever one or more cards leave your graveyard, you may create a 1/1 black and green Insect creature token, then put a number of +1/+1 counters on it equal to the greatest mana value among those cards. Do this only once each turn.

Scute Mob

At the beginning of your upkeep, if you control five or more lands, put four +1/+1 counters on Scute Mob.

Hornet Nest

Defender (This creature can't attack.)
Whenever Hornet Nest is dealt damage, create that many 1/1 green Insect creature tokens with flying and deathtouch. (Any amount of damage a creature with deathtouch deals to a creature is enough to destroy it.)

Zask, Skittering Swarmlord

You may play lands and cast Insect spells from your graveyard.
Whenever another Insect you control dies, put it on the bottom of its owner's library, then mill two cards. (Put the top two cards of your library into your graveyard.)
{1}{B/G}: Target Insect gets +1/+0 and gains deathtouch until end of turn. ({B/G} can be paid with either {B} or {G}.)