Insects and Fungi

Our June general meeting was an online meeting because of restrictions on gatherings due to the COVID-19 pandemic. The topic for the meeting was a presentation entitled ‘Insects and Fungi’ delivered by Daniel Heald (a KRMB Member). It was great to see so many people log on to the meeting, including a previous KRMB regular, Dr Norm Pinski, who logged on from Nova Scotia, Canada!

Daniel explained that there were many aspects to the Insect/Fungi relationship. His PowerPoint presentation started with a discussion of Fungivores. These include the Mycetophilidae – Fungus gnats and Sciaridae – Dark winged Fungus Gnats. The larvae of both species feed on the fruiting body and mycelium of the fungus. Sciaridae larvae are pale and translucent. Also in this group are the Heteromyzidae – Sun Flies, which include Tapeigaster species. Some beetles are also fungivores. These include the Endomychidae – Handsome Fungus Beetles, the Erotylidae or Pleasing Fungus Beetles and Tenebrionidae (Bolitophagini) – Forked Fungus Beetles such as Byrsax species. Other fungivores include the Achilidae – Fungus Bugs, Aradidae – Flat Bugs, Timeidae – Fungus Moths (such as Nemapogon granella, a world-wide nuisance). Euprenolepsis procera are ants that feed exclusively on fruiting bodies of fungi, while Springtails thrive on a diet of fungal spores.

Daniel explained that insects do not have it all their way; there are some parasitic fungi that attack insects. These include fungi in the order Laboulbeniales, colloquially called Labouls, such as Fly Destroyer Fungus and Massospora cicadina, which infects periodical cicadas, the fungus develops inside the Cicada larvae and after the adult emerges it causes the back end of the abdomen to fall away exposing a plug of fungus, which then produces spores causing the cicadas to become ‘Flying Salt Shakers of Death’. Also included in this group are Cordyceps and other entomopathogens such as Cordyceps gunnii. Daniel showed several photos where the fruiting body of the Cordyceps gunnii was sprouting out of the insect host.

Daniel explained that there are also many examples where the fungi and insects have a mutualistic relationship. He used the example of Leaf Cutting Ants and Termitomyces species fungi (a very large fungus with lots of spores that get spread around a large area). The fungus breaks down the leaf matter carried in by the ants, who in turn spread the fungal spores on their foraging trips and the ants get some nutrients from the fungi.

The Veiled Stinkhorn attracts flies and other insects to a spore-containing slime and the flies eat the spores and disperse them. Some fungi use insects to transport spores, for example Melampsora ricini, Castor Leaf Rust, is attractive to Honey Bees, which then unwittingly pick up the spores and disperse them.

Puccinia species infect a host plant, such as Arabis species (Mustards) and inhibit the host plant’s ability to produce flowers. Instead, the fungus produces pseudoflowers that are attractive to insects. Insects that visit the pseudoflowers transport spermatia from one host plant to another.

The Sirex woodwasp, Sirex noctilio, kills healthy pine trees by introducing a wood-rotting fungus and toxic mucus into the tree. This fungus introduced by the female wasp spreads throughout the tree and provides food for the burrowing Sirex larvae. Ambrosia Beetles, such as Xylosandrus crassiusculus, introduce symbiotic fungi into a tree that is to host the development of its larvae. Both the adult beetle and larvae then feed on the fungi. However, alcohol rich secretions from the fungus can become a problem for the tree.

Daniel finished his presentation with a discussion on parasites by proxy. One such species is the Ash Tree Bolete, Boletinellus merulliodes, the fruiting bodies of which are found under Ash trees. However, it does not have a mycorrhizal association with the tree, rather it feeds on sugary secretions from the Ash Tree Aphids that feed on the root system of the tree. Another example is Sepobasidium species (Bracket fungi) that use scale insects to bore into wood then grow over and into the hole.

It was a fascinating presentation and provided the audience with another reason to study fungi closely over the next couple of months. All online thanked Daniel for an excellent presentation.

Colin Prickett