Species Pterotermes occidentis

Termes occidentis Walker, 1853

Termopsis occidentis Hagen, 1858

Kalotermes occidentis Banks and Snyder, 1920

Pterotermes occidentis Walker, 1853(1)

Monotypical genus

One species in our area(1)

See: Kalotermitidae

Largest Kalotermid of its region.

Alates posses large circular black eyes, the ocelli are white, prominent and raised, right above eye. Compared to other Kalotermids of the region, the pronotum is more or less flat and does not wrap around extensively on the sides, and with no corners. Orange in colour.

Soldiers of Pterotermes occidentis can be easily distinguished from other Kalotermitidae by the clear V-shaped concave anterior margin of their massive pronotum and the presence of prominent wingbuds. The head is rounded, and flat dorsally, with the mandibles attached at an angle. Eye spots are prominent whereas they are usually not noticeable on most other termites of the region.

Southern Arizona and Western Texas.

Also found in Baja California and Mexico; occupies the Sonoran desert.(1)(2)

This species has been noted for its extreme tolerance to desiccation and its intolerance to moisture. It is thus restricted to the Sonoran desert and other desert habitats due to heavier rainfall outside of the desert.(2)

Nests

P. occidentis constructs extensive haphazard galleries and often uses galleries left by other termites and beetles. Typically the tunnels are no smaller than 3x5 mm. The galleries are irregular chambers, with a characteristically rough surface.

Although the galleries remain mostly free of fecal pellets, abandoned chambers are used to store fecal pellets or store deceased members in outbreaks of microbial infection due to moisture. Like other drywood termites they construct “kick out holes” to expel unwanted fecal pellets. Semi-wet fecal pellets are used to seal up holes or exits to the outside world or used to wall off abandoned chambers.(2)

This species flies during the night from mid-July to August, during the rainy season of the Southwest.(2)

As typical with other Kalotermids, they practice single piece nesting. They can live their entire lives within their food without making contact with the ground.

P. occidentis occupies a niche of colonizing extremely dessicated vegetation, dominating long after competing insects -including termites- have departed. Vegetation occupied by P. occidentis has often times been damaged extensively by other termites (Namely Heterotermes aureus, M. hubbardi and possibly Amitermes sp.) as well as beetle larvae (Cerambycidae and Buprestidae). In the case of the latter group, P. occidentis likely feeds off of the tightly packed sawdust of the larval galleries. Although colonization likely starts before these optimal dessicated conditions.(2)

Hosts

This species has been recorded in the following plant species:

And various records in dead and alive “Palo verde trees (Most likely Parkinsonia spp.)” and “Yucca”.(2)

See: Termites: Lifecycle

P. occidentalis has long been regarded as one of the most primitive drywood termites, especially behaviorally. As such mature colonies devote the majority of their resources to alate production. Alates disperse in somewhat localized intervals throughout their flight season and a single colony does not tolerate more than one reproductive pair.

Egg production of established colonies declines during the fall and comes to a halt during winter, resumes during the spring, around April or May. As with other basal termites colonies remain flexible with alate production and mature colonies devote most of their resources towards alate production.(2)

Swarming

Alates search for nesting sites separately, and do not seem to rely on pheromones nor do they engage in tandem running. Often flying from host to host. Once a suitable crevice or hole is discovered, it is inspected, resulting in settlement or continued searching. Wing removal occurs either by the act of inspecting a hole or are manually removed via bodily movements. P. occidentis has never been recorded to bore into wood but will dig into an already existing cavity.(3)

After around 12 - 72 hours of digging the holes are plugged with a gut contents.(3) This plug which seems distinct from normal semi-wet frass has also been noted and employed the same way in other Kalotermids.

Infestation likely occurs before optimal desiccation has been achieved.

Founding

Initial egg production and colony founding is tediously slow, even among desert drywood termites. Colonies number from zero to a dozen offspring during the first year.(2)

Despite their intolerance to moisture individuals have been recorded to enthusiastically and readily drink free water (i.e water droplets). Although prolonged exposure to moisture inevitably results in colony death and eventual takeover by microbes. It is possible that this not only represents a behavioural adaptation to capitalize on water but an anti-microbial adaptation. The same behaviour and outcome has been observed in the Kalotermid Incisitermes minor, the western drywood termite.(2)

Castes

Worker caste: Lack of true worker caste; pseudergates. Eyespots present but without wingpads.

Nymphs: Differs from pseudergates by possession of wingbuds, molts into alates.

Reproductive castes

Imago: Derived from the nymphs

Neotenic: Brachypterous, very pigmented (brownish in colour). Derived from the pseudergates.

Soldier caste: May possess wingbuds. Derived from the pseudergate caste. Comprises around 2% of the colony population. Soldiers are likely only employed to plug exits to the outside world (i.e kickout holes or flight holes) and not predominantly used in intercolonial warfare.

Interaction with other organisms

Marginitermes hubbardi

Colonies have been recorded in wood simultaneously infested with Marginitermes hubbardi.(2)

Paraneotermes simplicornis

The two species attack palo verde trees but do not occupy the same part of a host, with P. simplicornis occupying near the roots and P. occidentis colonizing via the branches. Saguaro cacti occupied by P. occidentis is not occupied by P. simplicornis.(2)

Intraspecific

Aggression is variable between colonies. Colony on colony encounters likely result in fusion with the possible deaths of some or all of the current reproductives. In this regard their behaviour is similar to other dampwood and drywood termites such as Cryptotermes and Zootermopsis.

Incisitermes banksi