Mazirek, Kraul Death Priest

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

Arcbound Stinger

Flying
Modular 1 (This creature enters with a +1/+1 counter on it. When it dies, you may put its +1/+1 counters on target artifact creature.)

Carrion Grub

Carrion Grub gets +X/+0, where X is the greatest power among creature cards in your graveyard.
When Carrion Grub enters, mill four cards. (Put the top four cards of your library into your graveyard.)

Hornet Queen

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

Bane of the Living

Morph {X}{B}{B} (You may cast this card face down as a 2/2 creature for {3}. Turn it face up any time for its morph cost.)
When Bane of the Living is turned face up, all creatures get -X/-X until end of turn.

Ambush Krotiq

Trample
When Ambush Krotiq enters, return another creature you control to its owner's hand.

Search for Blex

Look at the top five cards of your library. You may put any number of them into your hand and the rest into your graveyard. You lose 3 life for each card you put into your hand this way.

Blex, Vexing Pest

Other Pests, Bats, Insects, Snakes, and Spiders you control get +1/+1.
When Blex, Vexing Pest dies, you gain 4 life.

Blex, Vexing Pest // Search for Blex

Grave-Shell Scarab

{1}, Sacrifice Grave-Shell Scarab: Draw a card.
Dredge 1 (If you would draw a card, you may mill a card instead. If you do, return this card from your graveyard to your hand.)

Carrion

As an additional cost to cast this spell, sacrifice a creature.
Create X 0/1 black Insect creature tokens, where X is the sacrificed creature's power.

Bond Beetle

When Bond Beetle enters, put a +1/+1 counter on target creature.

Deadly Insect

Shroud (This creature can't be the target of spells or abilities.)

Living Hive

Trample
Whenever Living Hive deals combat damage to a player, create that many 1/1 green Insect creature tokens.

Deadbridge Goliath

Scavenge {4}{G}{G} ({4}{G}{G}, Exile this card from your graveyard: Put a number of +1/+1 counters equal to this card's power on target creature. Scavenge only as a sorcery.)

Bayou Dragonfly

Flying; swampwalk (This creature can't be blocked as long as defending player controls a Swamp.)

Ant Queen

{1}{G}: Create a 1/1 green Insect creature token.

Brain Maggot

When Brain Maggot enters, target opponent reveals their hand and you choose a nonland card from it. Exile that card until Brain Maggot leaves the battlefield.

Beacon of Creation

Create a 1/1 green Insect creature token for each Forest you control. Shuffle Beacon of Creation into its owner's library.

Devouring Swarm

Flying
Sacrifice a creature: Devouring Swarm gets +1/+1 until end of turn.

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.)

Iridescent Hornbeetle

At the beginning of your end step, create a 1/1 green Insect creature token for each +1/+1 counter you've put on creatures under your control this turn.

Broodhatch Nantuko

Whenever Broodhatch Nantuko is dealt damage, you may create that many 1/1 green Insect creature tokens.
Morph {2}{G} (You may cast this card face down as a 2/2 creature for {3}. Turn it face up any time for its morph cost.)

Caustic Crawler

Landfall — Whenever a land you control enters, you may have target creature get -1/-1 until end of turn.

Golgari Longlegs

Decimator Beetle

When Decimator Beetle enters, put a -1/-1 counter on target creature you control.
Whenever Decimator Beetle attacks, remove a -1/-1 counter from target creature you control and put a -1/-1 counter on up to one target creature defending player controls.

Blister Beetle

When Blister Beetle enters, target creature gets -1/-1 until end of turn.

Caustic Caterpillar

{1}{G}, Sacrifice Caustic Caterpillar: Destroy target artifact or enchantment.

Adaptive Shimmerer

Flash
Adaptive Shimmerer enters with three +1/+1 counters on it.

Giant Caterpillar

{G}, Sacrifice Giant Caterpillar: Create a 1/1 green Insect creature token with flying named Butterfly at the beginning of the next end step.