Giant Ankheg

Trample
Ward {2} (Whenever this creature becomes the target of a spell or ability an opponent controls, counter it unless that player pays {2}.)
Other creatures you control have trample and ward {2}.

Battlefly Swarm

Flying
{B}: This creature gains deathtouch until end of turn.

Brass Gnat

Flying
This creature doesn't untap during your untap step.
At the beginning of your upkeep, you may pay {1}. If you do, untap this creature.

Dark Ritual

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}.)

Carrion Beetles

{2}{B}, {T}: Exile up to three target cards from a single graveyard.

Swarmyard

{T}: Add {C}.
{T}: Regenerate target Insect, Rat, Spider, or Squirrel. (The next time it would be destroyed this turn, instead tap it, remove it from combat, and heal all damage on it.)

Giant Adephage

Trample
Whenever this creature deals combat damage to a player, create a token that's a copy of this creature.

Clockwork Beetle

This creature enters with two +1/+1 counters on it.
Whenever this creature attacks or blocks, remove a +1/+1 counter from it at end of combat.

Bond Beetle

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

The Swarmweaver

When The Swarmweaver enters, create two 1/1 black and green Insect creature tokens with flying.
Delirium — As long as there are four or more card types among cards in your graveyard, Insects and Spiders you control get +1/+1 and have deathtouch.

Gene Pollinator

{T}, Tap an untapped permanent you control: Add one mana of any color.

Plague Beetle

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

Caustic Caterpillar

{1}{G}, Sacrifice this creature: Destroy target artifact or enchantment.

Scute Mob

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

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.

Grist, the Plague Swarm

+1: Create a 1/1 black and green Insect creature token, then mill two cards. Put a deathtouch counter on the token if a black card was milled this way.
−2: Destroy target artifact or enchantment.
−6: For each creature card in your graveyard, create a token that's a copy of it, except it's a 1/1 black and green Insect.

Grist, Voracious Larva

Deathtouch
Whenever Grist or another creature you control enters, if it entered from your graveyard or you cast it from your graveyard, you may pay {G}. If you do, exile Grist, then return it to the battlefield transformed under its owner's control.

Grist, Voracious Larva // Grist, the Plague Swarm

Moldgraf Monstrosity

Trample
When this creature dies, exile it, then return two creature cards at random from your graveyard to the battlefield.

Bilious Skulldweller

Deathtouch
Toxic 1 (Players dealt combat damage by this creature also get a poison counter.)