Anacanthotermes

Anacanthotermes is a harvesting termite restricted to arid and semi-arid habitats. However, although sandy or gravelly soils are preferred, there must be some clay content in the soil as well as enough groundwater to allow some vegetation to grow (Harris, 1967; Roonwal, 1975).

Nests are always subterranean, with or without surface structures (Harris 1967, 1970; Roonwal, 1969). They consist of diffuse systems of small cells at various depths with interconnecting galleries. Storage cells with dry forage occur within the nest .

In A. macrocephalus, the surface mounds are low conical structures, made of loose earth ejected during gallery building activities. The structure is quite complex, however, with young mounds made up of an outer layer of earth particles and loose stones, and a more hardened sub-cylindrical plug. The plug appears to be made of earth particles stuck together, and is usually found at the apex of the mound. The plug may be hollow with a gallery leading to it, or soild, but it never has a gallery leading out to the exterior. Older mounds replace the plug with either a dome or core of compacted earth, around which the loose material is distributed. In older mounds a hole connects the base of the mound with the gallery system below. In the largest mounds, a shallow trough can sometimes be found under the mound base, within which a small number of workers and grass stems can be found. Other species are entirely subterranean with no above-ground sign of their presence (Harris, 1970).

Mound building is undertaken by pseudergates, and begins in late October and continues until March, during the cooler months of winter. Full details of mound building is given in Roonwal (1975).

Information on mound structure of A. macrocephalus is from Roonwal (1975).

The density of mounds can be high - Roonwal (1975) records 57 A. macrocephalus mounds in a 400 m-2 patch in Jodhpur district, India.

Anacanthotermes make extensive gallery structure in the soil around and under the mounds. The tunnels are narrow (5-10 mm diameter) and cylindrical or sub-cylindrical. They are distributed about 20-80 cm below the ground, and run horizontally parallel (or nearly parallel) to the soil surface. These horizontal galleries can run for 18-40 m, and may drop a few centimetres vertically from time to time. In addition, there may be connected chambers from which blind-ending vertical tunnels drop 1-2 metres to bedrock or gravel.

The galleries open to the surface beneath the mound and also at several places along the length of the horizontal tunnels, by means of short exit tunnels. These tunnels are normally sealed with earth, which is removed by pseudergates when foraging parties are about to leave the gallery system. The vertical galleries are of uncertain function, although they may be used by pseudergates to collect water as in some Macrotermes (ref). The function of the large chambers at the top end of the vertical chambers is also unknown, although Roonwal (1975) calls them assembly chambers and conjectures that they are used in the dry season as places for termites to congregate where water is readily available.

There are smooth-walled chambers of various sizes (2 x 3 cm to 7 x 12 cm) attached laterally (or by small tunnels) to the horizontal galleries. Distances between the chambers varied (in one 28 m long gallery) from 20 - 230 cm. The chambers are used for storing forage, usually with the largest chambers having the most material. The material within the chambers is usually a mixture of stems, grasses, seed husks, bark and herbivore dung. In wetter months, some of this material may be mixed with mound earth, apparently to help the plant material to dry.

Forages on dry grass and vegetable debris, biting off short lengths of plant material.

Workers forage in the open from late afternoon to early morning, and at all times of the day if they have constructed sheeting over the substrate. Functional compound eyes particularly well developed in Anacanthotermes species, and they presumably assist in foraging. Soldiers are rare.

In A. macrocephalus foraging from the colony centre may take place every day. Only workers forage, and soldiers are present in samll numbers, and only to guard - they are known to form a phalanx around the exit hole if the foraging party is disturbed (Gupta, 1959). Foraging workers usually emerge from one of the side passages mentioned above. Foarghing then takes place clsoe to the exit hole (10-50 cm away). Foraging times are influenced by the heat and humidity conditions, with foraging predominantly at night during hot summer periods, and throughout the day during colder, winter periods.

Foarging can last from 10 minutes to over an hour. Foragers generally take only dry structures and will not usually cut green plant material. Once the foraging has been completed pseudergates reseal the exit hole with saliva-wetted soil.

Winged adults swarm after the rain, during the day if humid or overcast, but otherwise at night (Roonwal & Rathore, 1975). Some imagoes shed their wings within colonies (rather than swarming) and subsequently act as workers.

In Anacanthotermes macrocephalus the dealates form into groups of 15-20 individuals which go underground and hide in crevices or under stones. There appears to be no pairing of males and females and no tandem running behaviour - this also true of other species (Harris, 1970). The groups (in the laboratory, at least) then dig into the soil. Roonwal & Rathore (1975) did not observe pairing in their laboratory colonies.

After digging into the soil the dealates dig a number of tunnels and chambers underground, and appear to remain together as a colony. Eggs are probably laid singly, and are collected together in masses of c. 150 eggs, apparently lightly glued together (full details of egg maturation and hatching are in Roonwal & Rathore, 1975). They seem to be cared for by the group as a whole, and upon disturbance single eggs are picked up by individual dealates and they are carried in their mandibles for some time. Dealates in colony groups also come up to the surface to forage like workers.

In Pakistan, species have been shown to significantly affect soil properties where they have worked the soil (Sheikh & Kayani, 1982). Valiachemedov (1981) discusses the role of A. ahngerianus in the formation of infertile Takyr soils in Central Asia, possibly due to an accumulation of salts in termite tunnels and termitaria.

Pal & Sharma (1971) present data on the seasonality of A. macrocephalus in Rajashtan, India, showing that termite populations in the soil are directly related to rainfall, and that the termites migrate down to a depth of greater than 90 cm in dry months, and may not be found in the soil at all in the driest months.

There are 10 Described Species.

Classification: 
Wed, 2009-01-21 15:41 -- Anonymous (not verified)

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