Site hosted by Build your free website today!


B. Fungal/ Insect Symbiosis & Commensalism

3. The Felt Fungi

4. Fungus Culturing Ants

5. Fungus Culturing Termites:


3. The Felt Fungi

Species of Septobasidium (Fig. 14-84) form a felty crust of growth over scale insects that infest plants, thus the name “felt fungi.” 

Fig. 14-84. Scale insects overgrown with Septobasidium pseudopedicellatum.

They are Basidiomycota closely related to rust fungi. Scale insects (Fig. 14-85) are “sap suckers” that extend their long snouts (probosces) into plant tissues to derive their nutrients. 

Fig. 14-85. A close up of the felt fungus showing numerous scale insects (arrows) attached to the twig.

Spores of the felt fungi germinate on the surface of young scale insects, send haustoria into their coelomic cavities, and thereby obtain their nutrient (Fig. 14-86)

Fig. 14-86. A cross section of a scale insect showing the  felt fungus covering it. Note, basidial and spore production on the surface. (See Couch, 1938)

Septobasidium will then form an extensive, felty, mycelial growth that will enshroud the scale insect. The fungus is biologically clocked to form basidia and spores on the felt surface at the time young scale larvae emerge from the felt and move on to new feeding sites. Once the scale insect sets up housekeeping at a new location, the spores will germinate and build a fungal house over the scale. Why did such an association develop? How does the scale insect benefit? The answer is, the fungus provides a home that protects the scale insect from birds and other prey and from stressful environmental changes. Likewise, the fungus is benefited by nutrients provided by the scale and dessimination of its spores to new feeding sites.

4. Fungus Culturing Ants

(Some of the images in this section came from:

 Leaf-cutting ants amaze us by their ability to cut and carry back to their nest leaf pieces 10 times their own weight (Fig. 14-87; Fig. 14-88; Fig. 14-89).

Fig. 14-87. A diagramatic sketch of the nest of leaf-cutting ants.

Fig. 14-88. The entrance to a leaf-cutting ant nest.

Fig. 14-89. A brush painting of a trail of leaf cutting ants.

 Dr. Neal Weber of the Department of Biological Science, Florida State University has done extensive studies on fungus culturing by ants. The leaf-cutting Attine ants have developed a mutualistic relationship in which the vegetative mycelium of a particular fungus is passed from one generation of ants to another solely through excretions. They grow the fungus on piles of leaf disks (Fig. 14-90)

Fig. 14-90. Ants tending the fungal garden within their nest.

The ants are unable to digest cellulose, but the fungus can and is thereby able to convert it into carbohydrates, fats and proteins that the ants can utilize. The larvae pick up the fungus as the mycelium proliferates in the ant galleries, forming large fungus gardens. These nests extend 3 meters or more underground (Fig. 14-91).  



Fig. 14-91. An excavated nest showing the details of a fungal garden.

Most of these fungi are wood-rotting basidiomycetes such as species of Rozites, Leucoagaricus (Fig. 14-92), and Lepiota (Fig. 14-93). 

Fig. 14-92. Leucocoprinus luteus, one of the mushrooms cultivated in the fungal garden.

Fig. 14-93. Lepiotia cristatiformis, another mushroom cultivated by leaf-cutting ants.

The leaf pieces are carefully handled by the ants and put into special compartments, mixing them with saliva, and the ants actually inoculate the fungus into the newly acquired bits of leaves. The fungus is not allowed to grow to the surface of the ant mound by the continued licking and feeding of the ants. The basidiocarps sporulate annually, usually during the rainy season. Old, decomposed leaves are carried several meters away from their nest. To prevent invasion by other fungi, the ant colony produces more than 20 different antibiotics.

5. Fungus Culturing Termites:

 A similar mutualistic relationship occurs between termites and fungi. Two fungal groups are commonly found growing symbiotically with termites (Fig. 14-94), Termitomyces (a mushroom) and Xylaria (a stromatic Ascomycete, the “dead man’s fingers”). 

Fig. 14-94. A queen termite with workers, reproductives, and soldiers. (Provided by Barbara Thorne)

Species of Termitomyces are some of our largest mushrooms, reaching 100 CM in diameter on African termite mounds (Fig. 14-95, Fig. 14-96)

Fig. 14-95. Giant termite mounds typical in Nigeria and other African countries. (Photo by Bob and Joann Parham)

Fig. 14-96. Termitomyces robustus, one of the mushrooms cultivated by mound-building termites.

This mushroom is the favorite species used for food by the Yoruba tribe in Nigeria. A very popular mushroom in China is the jizong mushroom, Collybia albuminosa, a shaggy capped fungus that grows in association with 7 different species of termites. It appears in the mountainous areas after torrential rains and for several weeks serves as the dominant food for monkeys in the areas.

The size and complexity of termite nests are remarkable (Fig. 14-97)

Fig. 14-97. Some fungi associated with termites: A and B) Termitomyces letestui, C) T. microcarpus, D) Podaxon pistillaris.  (Sands, 1969. Academic Press)

An interesting aspect of this complexity is the thermoregulation within the nests. Mound shape is determined by the climate and locality of the mound because it is important that the fungus garden be kept at a comfortable temperature. This is done with a unique array of ventilation chambers in the nests. If it gets too cold, the termites place obstructions in the vents to maintain warmth. When temperatures rise during the day, the vent closures are removed and cooling can commence. Isn’t that neat! Is this where GE gets their ideas? Guess what? In Zimbabwe, they have built office buildings using this same thermoregulation principle and have found that these buildings require less than 10% of the energy requirements that are demanded in traditional buildings; and all because the termites had to keep their fungal gardens cool! (McNeil, 1997, NY Times, Green Building News). The fungus gardens in termite mounds are very similar to those of leaf-cutting ants in that the termites have designed special compartments for the fungi and give special nutritional treatment for colony growth. The fungus in turn provides food and special chemical metabolites that influence the reproductive dynamics of the termite colonies. The cellulosic and pectinolytic enzymes of these wood-rotting fungi help to break down the substrates for termite use.