This is a termite

Termites are fully social insects, with an extraordinary range of morphological
forms. It is now clearly established that they are a very specialised form
of cockroach, with far more complex social systems than other cockroaches, and
with a far wider range of diets. Termites all live in colonies, with reproductives
(kings, queens, and nymphs), soldiers and “helpers” (true workers and also immature
stages that assist within the colony to some extent). Termite morphological and
anatomical adaptations are caste-specific, with structures evolving independently
in reproductives (to allow dispersal, pair bonding and fecundity), workers (foraging
and feeding, tending and feeding of immatures, nest construction) and soldiers
(only defence). The modifications seen in termite societies are similar to those found
in the somatic parts of multicellular organisms, leading to the idea that a termite
colony is best thought of as a single organism (or, more controversially, a “superorganism”).
The structures that termites build, the mounds and nests, might also be
defined as part of this organism. Mounds and nests contribute greatly to the wellbeing
of termite colonies by providing shelter, fortifications and climate control.
Overall, termites have amongst the most complex social, anatomical and structural
adaptations of any animal.

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Historically, termites and ants have often been considered analogous because they
share some characteristics in morphology and social organization, despite being
phylogenetically distant (Wilson 1971). However, an important difference is seen
in their postembryonic development: termites are hemimetabolous, while ants are
holometabolous. Furthermore, although alate termites show essentially “normal”
hemimetabolous insect development, juveniles and other castes (such as workers,
nymphs, and pseudergates) can have unpredictable and unique molting patterns,
such as stationary/regressive, reproductive, and soldier molts. Supplemental or
replacement reproductives also sometimes emerge, but with less predictability.
Supplemental reproductives (also referred to as “neotenics”) can function as queens
or kings, but often lack imaginal characteristics like wings or well-developed
compound eyes (Weesner 1969; Wilson 1971; Thorne 1996). Soldier differentiation
is the most specific developmental process seen in termites. Some ants
also produce caste phenotypes specialized in defense but they are categorized
as major workers in most cases, and are essentially larger versions of normal
workers (Hölldobler and Wilson 1990). Thus, the worker/pseudergate, soldier and
neotenic pathways are unique to termites and are a large component of termite
sociality.

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The evolution of soldiers in Hymenoptera (ants) differs markedly from that of the
Isoptera (termites) (Fig. 5.5). While soldier castes occur in all extant termites except the more
highly derived genera of Apicotermitinae (where they are assumed to have been
secondarily lost), the majority of ants lack a distinct soldier caste (Wilson 1971).
Larger-sized worker castes, referred to as majors, are called soldiers when specialized
for defense of the colony (Fig. 5.4b). Thus, soldier castes in ants can have
similar morphologies to the other workers, some level of allometry, or complete
polymorphisms in which soldiers forms have greatly enlarged heads, mandibles, and
defensive glands (Oster and Wilson 1978; Hölldobler and Wilson 1990).

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Termite colonies are organism-like entities with strong division of labour between
different subcomponents. This leads to a wide range of anatomical and morphological
adaptations within each species, and therefore, within each individual termite
mound. Comparable variation between is only seen in other colonial organisms, particularly
other social insects (ants, corbiculate bees, vespids). However, none can
match the complexity of anatomical specialisation, body form and colony structure
of termites.

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The evolution of eusociality in insects remains one of the great mysteries in biology.
The central reason for excitement among social biologists relates to the evolution
of reproductive division of labor: Why have some individuals evolved to restrict or
forego their own opportunities to reproduce in order to help others? Eusociality has
evolved independently in a diversity of taxa, including Hymenoptera (ants, bees, and
wasps), Isoptera (termites), Thysanoptera (thrips), Coleoptera (beetles), crustaceans
(shrimp), and mammals (naked mole rats) (Sherman et al. 1991; Duffy 1996; Choe
and Crespi 1997). That eusociality occurs in diverse taxa, yet is a phylogenetically
rare event, suggests that uncommon suites of factors are responsible (Hansell
1987; Crespi 1996; Thorne 1997; Hunt 1999; Wilson and Hölldobler 2005a). Large
colonies with complex castes and behaviors are even rarer, having arisen only in the
Hymenoptera and Isoptera (Fig. 5.1).

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Attention has focused on the Hymenoptera due to their haplodiploid genetic system
and ease of study. Termites have received less attention, despite the fact that
termites are the only diploid group that form highly complex colonies and have
an extraordinary diversity of castes (Choe and Crespi 1997; Thorne 1997).

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