Inject Methods

"Injects" refers to using a queen's Spawn Larva spells on hatcheries to increase larva production.  This is a fundamental Zerg mechanic and it forms the foundation of the macro cycle for a Zerg player.  It is normal to be injecting 3-5 hatcheries and during the early and mid-game it is important to perform this task every 30 seconds without much delay.  A number of different methods have been developed by players to streamline this task and those methods will be the main focus of this post.

The question of how to perform an inject sequence is really the sum of 3 different questions:
  • How do I select my queens to inject?
  • How do I issue the Spawn Larva command?
  • How do I manage my camera location during this process to facilitate selecting the hatcheries?
Each inject method must answer these 3 questions, and for the most part the answers to each part can be mixed and matched among methods.  This guide will be broken into 3 sections:

  1. The three questions and their possible answers.
  2. Five examples of common inject methods.
  3. An in-depth discussion of wandering queens.

Selection Methods:

Manual - the queen(s) that are going to inject at a location are manually selected by clicking on them or boxing around them.

Individual Control Groups - each queen or each group of queens at a particular hatchery location has its own hotkey.  This is normally paired with the Double Tap camera control method.

One Control Group - all inject queens at all locations are on a single hotkey together.  Inject methods that use this tend to be the fastest but they are also the only ones to suffer from wandering queens. (See below.)

Command Methods

Manual - just press the command key for Spawn Larva and click the hatchery.

Shift-Queue - press the command key for Spawn Larva and then hold shift throughout the rest of the process.  Click on each hatchery that needs to be injected.  This is generally paired with a One Control Group selection method.

Rapid-Fire - The command key for Spawn Larva has been set up as a Rapid Fire key that also functions as a left click.  Holding down this key while mousing over a hatchery will rapidly issue Spawn Larva commands on that hatchery.  Sometimes set up on the mouse wheel.  Because Spawn Larva can be stacked on a hatchery, Rapid Fire is no longer viable with Single Control Group methods (it will produce Wandering Queens) and is only used with shift for dumping excess energy from local queens onto a local hatchery.  

Camera Management

Base Cams - The user presses a base cam key to change the view to the desired base and then performs the rest of the inject mechanic.

Backspace - The user presses backspace (or sometimes rebound to spacebar) to rapidly cycle the camera through base locations and performs the inject mechanic at each.

Double Tap -  Either an individual hatchery or a local queen or group of queens is on a hotkey per base, and this hotkey is double tapped to set the camera location.  This is most commonly used with the Individual Control Groups queen selection method.

Mini-Map -  The camera is not moved at all and the inject commands are issued to hatcheries by clicking on their locations on the mini-map.

II. Methods

Some common combinations are:

Base Cam/Manual

Selection Method: Manual

Command Method: Manual

Camera Management: Base Cams

Description: The user taps a base cam, select the queen, presses the inject hotkey and selects the hatchery.  Repeat for other bases.

  • Trains use of base cameras.  
  • Never produces wandering queens.  
  • Does not use up any hotkeys for inject queens.  
  • Provides a natural checkup on each base.  
  • Easy and intuitive to compensate for dead queens.
  • Simplest method to learn.

  • Slightly slower than some other methods.  
  • Inject queens are not readily available on a hotkey.  
  • Returning queens to station after pulling them for defense is a manual process.

Core Inject

Selection Method: Single Control Group

Command Method: Shift-Queue

Camera Management: Base Cams

Description: The user selects the inject queens control group, presses the command for inject, holds down shift, and then for each base to be injected taps the base cam and click the hatchery one time.  Base cameras are centered on the hatchery so the mouse does not generally need to be moved between clicks once it is in position.

  • Trains use of base cameras.  
  • Inject queens are readily available on a hotkey for defense.  
  • Returning queens to station after pulling them for defense can be accomplished by performing a normal inject cycle.  
  • One of the faster methods. 
  • Allows easily compensating for known dead queens.  
  • Provides a natural checkup on each base.

  • Can produce wandering queens.  
  • The tendency to cycle rapidly through the base cams can produce errors when compensating for dead queens and can limit the value of the natural checkup since the base is only in view very briefly. 
  • Requires some practice to get used to.

Hotkey Inject

Selection Method: Individual Control Groups

Command Method: Manual

Camera Management: Double Tap

Description: User double taps the control group for a queen at a base location.  This selects her and changes the camera to her location.  The user then presses the Spawn Larva command and clicks the hatchery.  This process is repeated for each queen at each base, although 2 queens injecting a main and macro hatchery at a base might share a control group.

  • Does not produce wandering queens.  
  • Inject queens are already on individual control groups for defense and returning them to their previous locations is fairly straightforward. 
  • Provides a natural checkup on each base.

  • Slower than some other methods.  
  • Uses up one control group per location being injected.  
  • Does not train camera hotkeys.  
  • Can fail to center camera on the base that needs to be injected if the queen has been moved for defense or killed.

Backspace Method

Selection Method: Single Control Group

Command Method: Shift-Queue

Camera Management: Backspace

Description: This is pretty similar to the Core Inject.  The user selects the queen group, presses the Spawn Larva command, holds shift, and then for each base taps Backspace and then click the hatchery.  It is common to re-bind backspace to spacebar for convenience.  This method used to be paired with Rapid Fire but that is no longer viable in LotV.  

  • Extremely fast in simple scenarios where every base needs to be injected.  
  • Inject queens are already on a control group for defense.  
  • A normal inject cycle can be used to return queens to their station after pulling them for defense.  
  • Provides a brief checkup on each base.
  • Backspace naturally centers the camera on the hatchery.

  • More prone to wandering queens than most methods.  
  • Does not train camera hotkeys.  
  • Takes camera to all bases, not just the ones that need to be injected.
  • Requires some practice to get used to.

Mini-map Method

Selection Method: Single Control Group

Command Method: Shift-Queue

Camera Management: Click hatchery on mini-map.

Description: User select the queen group, presses Spawn Larva command, holds shift, and then clicks on each hatchery to be injected on the mini-map.  Hatcheries will be the largest squares and the target reticle will indicate when a valid target is being hovered.  The camera is not moved.

  • Pretty fast, depending on speed and accuracy of the mouse-hand to select hatcheries on the mini-map.  
  • Can be done without taking eyes off of a battle or scout.  
  • A normal inject cycle can be used to return queens to their station after pulling htem for defense.

  • Does not train base cam usage.  
  • Does not provide a base checkup.  
  • Does not provide visual indication of wandering queens when that happens.  
  • Can be slow if the user is not good at clicking hatcheries on the mini-map.

Alternative combinations

These are just some common examples.  Other combinations are possible.  One could use the Backspace camera with manual selection and command, or One could Double Tap and then use Rapid Fire to perform the actual inject.  One could use Individual Hotkey selection and Manual injection via the Mini-map.  These are all valid methods, but they may lack defining strengths to promote their use.

III. Wandering Queens

A problem that is common to all Single Control Group methods (and only to those methods) is wandering queens.  When Smartcasting decides to assign an inject command to a distant queen rather than a close queen, that distant queen will walk to the selected hatchery and inject it.  Because Smartcasting prefers to use a local queen when she has enough energy and is available for the command, this only happens in some specific situations:

Low energy
If the local queen has less than 25 energy the command will go to a more distant queen with enough energy if one exists.  That queen will then wander to this hatchery.

If the local queen no longer exists because she has been killed then the command will go to another queen, if possible.  Not being in the inject control group will create the same impact.

Smartcasting prefers to issue a shift-queued command to a caster that is not already trying to execute another command, and the command is not considered completed and the queen "available" again until the entire Spawn Larva animation is completed.  So if there is one queen near a hatchery and you quickly shift-queue two injects on it, the local queen will receive the first one and a remote queen, if available, will receive the second command and wander.

If every queen is busy then the second command will go to the closest queen again.  Because of this if all queens have 50 energy and the user performs a complete inject cycle twice the queens will not wander, but if the user performs a single inject cycle and clicks each hatchery twice they will.


Wandering queens can be 100% avoided by not injecting when there is not enough energy, not injecting hatcheries where a queen is missing (e.g. dead), and not injecting more than once per cycle.


Once a queen wanders, all subsequent queens in the sequence will also wander because now her hatchery is vacant.  


User has four bases and four inject queens.  The queen at the natural is killed by harass and the user performs a normal inject cycle that does not account for this.

The main will be injected normally.  There is no queen at the natural so the queen at the 3rd will wander to the natural and inject there.  Now the 3rd queen is busy so the inject on the 3rd gets assigned to the queen for the 4th and it also wanders.  The inject for the 4th fails if none of the queens have enough energy for a 2nd inject, otherwise the queen Smartcasting chooses will wander to the 4th and inject there.


Because of the way wandering cascades, if there is a wandering queen problem then when the last hatch inject command is given that queen will be observed to either be walking away or already misssing.  If this is not the case, if she just injects her hatch normally then the user can be sure that no queens are wandering off-station anywhere.


If the cause is insufficient queen energy then the user just needs to be more careful with inject timing.  One possible solution is to put the inject queen with the lowest energy on a separate control group and check it periodically.  When she has >=25 energy then all inject queens do and the inject can be performed.

If the cause is missing or dead queens, which is to say that there are fewer queens in the inject control group than there are hatcheries to be injected, then the solution is to either get more queens or inject fewer hatcheries.  More queens can be built, or creep queens can be put into to the inject group, or both.  The most efficient solutions will involve identifying which hatcheries are missing queens and getting a queen on station at that location manually.  But if the user is overwhelmed or otherwise does not want to deal with this it is sufficient to get the correct number of queens in the inject control group and then perform an inject cycle normally when they have enough energy.  This is described below in Return to Station.

Return to Station

"Wandering" can also be used as an advantage.  If queens have been pulled for defense, or new or creep queens have been added to the inject control group, it is not necessary to manually put them back on station for injects. The user can just perform a normal inject cycle.  One queen will receive the command for each hatchery and walk to that location.  This will put one queen on station at each hatch as long as the number of queens in the inject group is the same as the number of hatcheries to be injected.  Some inject time will be lost while the queens travel as compared to putting them on station manually and ahead of time to inject, but if the user is strained for APM this may be a worthwhile tradeoff.


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