Authored by: survivor6570, with contributions from .monsi, nuloen, and zornmauser.

Introduction

Phylogeny is the relationship between different species or subspecies, usually depicted as a tree.

In the absence of concrete genomic analysis of Terminids, classifications can only be made through phenotype, behaviours, and apparent hierarchies as observed on the field by SEAF forces and Ministry of Science researchers.

Firstly, three main categories of Terminid are immediately apparent; the baseline Terminids, the bile Terminids, and the pouncing Terminids.

Whether or not Terminids are actually a single species is entirely dependent on which definition of species an individual attempts to use; some species show a great divergence of phenotypes (such as domesticated felines, canines, and even humans themselves) whilst others are very uniform. The fact that Terminids all appear to interact and co-exist peacefully is indicative that they are likely all a single species, split into different phenotypic lineages, which may colloquially be referred to as “strains”.

Furthermore, it seems evident that Terminids are in all likelihood a eusocial species, like terran ants, albeit no actual evidence exists of a Terminid queen, and Terminids do not appear to lay their eggs, rather their egg clusters bear striking similarity to certain fungal rashes.

Here are all known strains:

• Scavengers
• Warriors
• Hunters
• Spewers
• Brood Commanders
• Stalkers
• Chargers
• Titans

These are however very vague and mostly superficial classifications which do not account for the apparent phylogeny between certain groups.

The following is the proposed classification of all currently observed Terminid strains, as refined in the lore channel of the Helldivers discord. It is subject to change.

Baseline Terminids

• The Scavenger
• The (Alpha) Warrior
• The Hive Guard
• The Nursing Spewer
• The (Alpha) Brood Commander
• The Charger (Behemoth)
• The Impaler

Pouncer Terminids

• The Pouncer
• The Hunter
• The Shrieker
• The Stalker

Bile Terminids

• The Bile Spitter
• The Bile Warrior
• The Bile Spewer
• The Spore Charger

Others

• The Bile Titan
• The Spore Spewer
• The Shrieker Nest

The reasoning for the above shall be clarified in the following explanations of how these categories were established, how they interact, and what their apparent phylogeny is.

What exactly is a Terminid?

I feel it is also important to add that Terminids can be best described in Terran terms, overall, as crustacean mushrooms with the social characteristics of ants that produce excessive amounts of oil.

In more scientific terms; a carbon-based life-form with a crustacean morphology that reproduces via spores and exhibits eusocial behaviour, whose decomposing biomass produces a great quantity of the E-710 compound.

I have opted to name this species Xenosagaricomycetes Brachyuraformicidae, which translates roughly to something along the lines of alien ant-crab mushroom.

The following is a phylogenetic tree to summarise this entire document:

Fig. 1: Phylogenetic lineage of all observed Terminid morphs.

Baseline Terminids

The Scavenger

Whilst many consider scavengers to be a juvenile stage for Terminids, I feel that this sentiment is wholly inaccurate. Some Terminid variants do exhibit morphological continuity that suggests progressive stages of maturity in a strain, but this does not inherently mean the Scavenger is such a strain.

Ants do not allow their juveniles to leave the nest; I see little reason why the Terminids should be any different. In fact, there is only limited morphological continuity between scavengers and warriors. The scavenger is a fully adult strain of Terminid; one that is simply geared towards scavenging rather than combat, much like a worker ant differs from a soldier ant without being a juvenile.

However, scavengers do exhibit traits that suggest nursing spewers are at least a direct evolution of the scavenger, geared towards more optimized regurgitation of material, likely for the feeding of underground larvae (hence its name).

The Warrior

Warriors are a common foe for Helldivers; they are most often found escorting patrols of scavengers across terrain, milling about in surface nests, and as one of the first responders during a bug breach. Whilst they present the obvious morphological similarities to scavengers like any members of a same species would, they are entirely different castes and, I cannot stress this enough, wholly separate strains. Warriors present far greater morphological continuity with Brood Commanders; of which they are likely to be a junior strain. Juvenile warriors or juvenile Terminids of any kind are unlikely to ever leave the nest!

In any case, Warriors are clearly analogous to the soldier caste of ants; they assure protection for the hive and for less well-armed phenotypes like the Scavenger, and present great tactical coordination in groups, with a penchant for surrounding a foe.

The “Alpha” strain of the warrior is the clear “missing link” between the warrior and brood commander stage of a Terminid combatant’s life. It shares the morphology of a warrior but has already taken on the pigmentation of the brood commander it will eventually become. This observable continuity between all the stages of a warrior’s life is one of the reasons I am strongly sceptical of the claims that bile spitters may become bile spewers for the time being.

The Brood Commander

To anyone with keen eyes, the Brood Commander appears simply as an older, more mature warrior; their greater size preserves exactly the same dimensions, and the darkening of their pigmentation is consistent with the same morphological evolution present in many Earth-based species as they grow older. They are essentially just the senior strain of warriors, and behave as such; their apparent command over younger warriors implies some kind of age-based hierarchy within Terminid hives, at least for military matters. They are also found escorting scavengers, and exhibit exactly the same behaviours as warriors in combat, attempting to surround an enemy alongside the younger Terminids, whilst seemingly also providing greater cohesion to Terminid combatants in its vicinity.

The “Alpha” strain of the brood commander is the apparent final stage of maturity for a Terminid warrior. It features more defined horn-like protrusions and even sharper claws. It is likely that the individual Terminid warrior will die not long after attaining this final stage of its life.

Nursing Spewers

An apparent divergence from the scavenger strain, it is unknown whether it is a later stage of the scavenger's life or simply a highly specialised evolution derived from the basic scavenger phenotype. I lean towards the latter explanation, as whilst bile spitters may at first glance indicate spewers are a later stage of life for smaller Terminids, there are discrepancies I shall touch upon in their respective sections.

Nursing spewers regurgitate biomass in great quantities; likely for the larvae in the nests (hence their name). They are extremely well-optimised for this task, which implies a process of natural mutation rather than artificially induced mutation like the bile spewers- which I shall again, elaborate in their respective section. Whilst the substance they regurgitate is highly corrosive, it seems that unlike bile spewers, nursing spewers regurgitate actual bile, which is an alkaline substance serving to break down nutrients in the intestines in Earth-based life forms, and likely fulfils the same or a very similar role in Terminid anatomy. They are often found in the company of other Terminids and generate a mysterious spore cloud which may be linked to ill-understood Terminid reproduction.

The Hive Guard

As its name suggests, this variant is most commonly found in hives, and likes to loiter around nests. Their exclusively front facing armour is an optimisation unlike that of any other Terminid strain; they are effectively completely unarmoured from the rear. It seems evident that hive guards, a strain not present during the first galactic war, were almost certainly evolved as a counter to the cherished SEAF passtime of throwing a grenade down a bughole, as they are able to block the entrances to nests almost completely with their thick layer of forward armour when they settle into a defensive posture.

Strangely enough, there does not appear to be any later stages of maturity for hive guards that have yet to be observed. Some scholars have suggested that the Hive Guard is the junior lifestage of the Impaler and the Charger, but I find the evidence to suggest this and the logical deductions employed to be insufficient.

The Charger

How and why chargers evolved is a mystery. What use walking tanks could possibly have been for the Terminids is consigned to be lost in their pre-contact history. Some researchers have theorised that their head resembles a plough or a shovel of some kind, which may indicate they are actually one of the primary Terminid morphs for establishing the subterranean tunnels of the hives.

Be that what it may, their role as a walking tank has made them proficient at being a problem for SEAF personnel unless anti-tank weaponry is nearby. Their thick, chitinous shell two-dozen centimetres thick in places, granting them near-immunity to anything short of dedicated AT, save for their moderately exposed underside, which is difficult to access unless one brings along anti-tank mines or you are exceptionally lucky.

Three overt variants of chargers exist, but there is strong evidence that impalers constitute a fourth, somewhat more subtly.

The basic charger is an all-black 5-ton tank not dissimilar to an oversized rhinoceros. They exhibit behaviour consistent with territorial bovines and are seemingly a variants of Terminid combatant, though no juvenile stage of the charger has ever been witnessed, which implies they are kept underground until sufficient maturity, perhaps because their thick, chitinous exoskeleton takes a significant amount of time to harden relative to other strains.

The “Behemoth” Charger is merely an older stage in the life of a charger; it has thicker armour, sharper horn-like protrusions, and a distinctly more plough-like head with a greater resemblance to a rhinoceros, as well as two tusk-like protrusions around the mouth. Much like elephants use their tusks to dig, it is possible these further establish the charger’s role as a Terminid drill of sorts.

The Impaler

Whilst a controversial assertion, the idea that the Impaler is a divergent charger strain is not so strange once a concrete analysis of its physiology is made.

Appearing brown under certain lightings, it is actually a closer colour to the dark grey of the Charger, and if one is lucky (or unlucky) enough to witness the face beneath the tentacles, it has the same mouth as a charger, with the same exact pincer morphology.

Whilst much larger than behemoths or standard chargers, a case could be made that Impalers are a distinct strain that evolved from chargers, rather than any kind of elder stage in a charger’s lifespan.

In terms of behaviour, the Impaler presents the ability to stomp as a warning or a devastating attack, and its ability to tunnel with its tentacles, if it is proven to be a charger strain, may support the idea that regular chargers and behemoths themselves evolved to dig tunnels.

Bile Terminids

The Bile Spitter

A colloquial name; the Bile Spitter does not actually spit bile, rather a mix of corrosive stomach acids. Again, it may be controversial of me to assert that these are not in fact a juvenile stage, but to me it seems evident that these were evolved alongside bile spewers rather than being a part of the bile spewer’s lifespan. Much how the bile spewer likely diverged from the nursery spewer, bile spitters likely diverged from the baseline scavenger, and remain an adult stage of the scavenger lifespan. It is nonetheless not implausible that they are a junior stage of the bile spewer, albeit this then poses the question; why are there no nursing spitters?

Perhaps because nursing spewers are not known to be capable of ‘artillery’, and thus may indeed be the later lifespan of scavengers; although I find that notion unlikely as the size difference is significant, although it is not impossible. Again, even were it the case, it is unlikely either scavengers or bile spitters are actually juveniles, but would then rather be simply junior stages of adulthood. The absence of nursing spitters alone, to me, is evidence the spitter and spewer are separate morphs whose evolution was simply convergent from scavengers and nursing spewers respectively, through the same environmental pressures; possibly artificially induced in nature.

Its role in the hive is likely not far removed from that of regular scavengers, and they can be observed traversing the surface in large patrols, often escorted by bile warriors and- or- bile spewers, much as scavengers operate.

The Bile Warrior

Morphologically identical to its baseline cousin, these are an evident mutation of the Terminid warrior strain. They present spore-like bubble growths along their lower abdomen, which explode upon death, releasing corrosive acid. They cannot spit or spew this acid, like spitters or spewers may.

Intriguingly, no bile variant of the alpha, brood commander, or alpha brood commander stages has yet been observed, indicating either that these are extremely illusive, or that bile warriors do not live long enough to mature into these stages once they hit their junior adult warrior stage.

The Bile Spewer

Bile spewers seem, at first glance, like green and up-armoured nursing spewers. However, they do not regurgitate food like nursing spewers, and are thus entirely useless for the task of nursing. This then poses the question; how did they mutate if they do not serve the same task?

Well, it seems likely that they are an artificially induced mutation of the nursing spewer, much like the bile spitter. And whilst many are quick to portray the bile spitter as a younger bile spewer, in reality we can observe younger bile spewers in certain contexts; these are identical to the older bile spewers in all but the armour plating they lack, and distinctly resemble the nursing spewers the strain likely diverged from. They are capable of both vomiting their bile, and of launching devastating ‘artillery’ projectiles from their rear abdomen, like a spitter.

It seems the only reason to preserve this mutation amongst the Terminids may have been defensive in purpose, as these are devastating counters to the long-range capabilities of the SEAF that would otherwise easily dispatch Terminids from afar.

Spore Chargers

Deceptively named, these are in fact a bile variant of regular chargers, and likely serve the same purpose, but are simply mutated. This mutation is likely sourced from the same environmental pressure- artificial or natural- that spawned the bile variant of the warrior strain.

Similarly to bile warriors, no further maturity stage of the spore charger has ever been observed (e.g. a spore behemoth), strengthening the possibility that both of these bile mutations are not conducive to a longlife in the affected Terminid.

Pouncer Terminids

The Pouncer

It is actually more probable that these are the junior stage of hunters, than only a scavenger mutation. However, their shared traits with scavengers could indicate as a consequence, that hunters did in fact evolve from the baseline scavenger themselves. There is also the possibility that there is no continuity with hunters, but again, in this instance, the evidence that opposes the idea is weaker than that which supports it.

Whilst they exhibit behaviours similar to scavengers when patrolling, they are much more aggressive, hinting at their combat-oriented role, and furthering the idea that they are a junior stage of adulthood for hunters. Much like hunters, they also pounce, giving them their name.

The Hunter

An aggressive, tactically cunning Terminid strain, their name suits them well. They pounce around, and are one of the more common combat strains that a Helldiver will encounter.

Whilst tempting to classify as a mutation of the warrior strain, this seems improbable for several key reasons; their exoskeleton is more consistent with that of scavengers, they are likely the senior stage of life for pouncers, and Stalkers are not in any way an older hunter. Hunters do not turn invisible, nor do pouncers. There is thus no brood commander analogue for Hunter evolution, ergo it is infinitely more likely that the pouncer/hunter are directly evolved as a mutation from the scavenger. Most Terminid morphs are, albeit in many different ways.

The Shrieker

The mysterious strain of flying Terminid almost beguets disbelief. Long thought to be a tall tale from delirious SEAF veterans or worse- dissident propaganda- the shrieker strain is in fact a mutation of the hunter strain, with greater wingspan and thus the ability to actually fly.

Their pigmentation is also somewhat intermediary between the pouncer and the hunter, further strengthening the idea that these are two stages of life for the hunter.

The Stalker

Utterly terrifying conceptions, how Terminid evolution devised this strain is something I do not wish to dwell upon, lest eldritch knowledge is uncovered. In any case, this is not a senior hunter. This myth is prevalent amongst SEAF personnel due to their shared pouncing behaviour, but is a product of ignorance. In reality, stalkers diverged from the hunter/pouncer strain, and have little in common besides colouration, pouncing, and acid spittle.

During the first galactic war, the Stalker and the Shadow could conceivably be identified as two stages of the same strain’s life, much like the pouncer and the hunter are simply stages of maturity (or as they were then known, the scout and the vanguard).

This is no longer the case. We know that experiments in gene splicing occurred on Terminids, and that the current Stalker strain is a product of these; but whilst many commonly assume that invisibility was what was achieved, this is incorrect. The true result of these experiments was the merging of the Stalker and Shadow into a single stage of life; the current Stalker, which exhibits morphological traits present in both of these previous stages of the strain’s life.

Its ability to spray an irritant from its saliva is shared with the hunter strain, although no other strain shares this trait (including the Bile Terminids, who spray an entirely different substance).

Others

The Bile Titan

Until such a day as a thing akin to a nursing titan is revealed to exist, then the bile titan shall elude classification amongst the other strains of Terminids. It exhibits shared traits and discrepancies with all the other strains, despite its deceptively simple allusion to pertaining amongst the bile family.

It would be easy to make such a classification, but the bile titan is simply not merely a Bile Terminid; it does not share any traits with the bile category other than spewing bile and the colouration of its chitin. It is comparable in underbelly coloration and overall proportions to pouncers, but; its thick chitinous armour, pincers, and head resemble the baseline terminids the most.

Furthermore, the Ministry of Science has firmly established that the mutated larvae extracted from certain missions against the Terminids by brave helldivers, is in fact a Bile Titan larvae. This alone implies a simple fact; there is potentially an entire tree of Terminid evolution only relating to titans, as a result of a relatively recent mutation.

The Spore Spewer & Shrieker Nest

Whilst you may be forgiven for assuming these are little more than a structure, the Terminids are a fungal species, and thus the giant mushrooms like the spore spewer and shrieker nest are an entirely living portion of their hives. How exactly these are related to the crustacean morphs remains a mystery for now, but it is indisputable that they are a Terminid lifeform of some kind, and part of the species classification. Much like the Bile Titan, they shall remain in this category of “others” until more information allows us to make new links to the main categories of Terminid strains we observe.

Credits

Written by:

Ministry of Defence Desk Jockey (survivor6570)

Special Thanks to:

//The Automatic Collective// (zornmauser)

Curiosity | SES Wings of Freedom (curiosity3494)

Pinky (pinkerypunkplonk)

Nuloen (nuloen)

Monsi | SES Hammer of the Orb (.monsi)

enxivity6579 (enxivity_6579)

Exponentveil525 (exponentveil)

Brood Commander (quiblirules)

Cmdr. Ramzies | S.E.S.F. (sgxr)

D.I.V.E. Super Private | Glitch (shadowtheglitch)

Woodwalker| SES Power of Science (woodwalker2211_29421)

Grand Lord Tad (tadeuszekpl)

Automatonic_Helldiver (lost_tapejara)

Human | Herald of the Orb (witness_of_dawn)

V | The Star of the Stars (thevirtualviewfinder)