Platypus apicalis
Platypus apicalis, known by its common name the New Zealand pinhole boring beetle, is a wood-boring beetle endemic to New Zealand and found throughout the North and South Island in a range of environments.
Description
The colour of Platypus apicalis is mainly dark-brown, with yellow basal joint of antennae, metathorax and femora. The body is cylindrical in cross section and greatly elongated from front to rear. It is less than 2 mmm wide and about 5.8 mm long. The mandibles of adults are oriented downward. The terminal segment of the antennae is dorso-ventrally flattened and larger than the other antennal segments. The mesothoracic wings are modified into a hardened wing case. A narrow longitudinal groove is present on the middle of the pronotum. The elytra bear parallel longitudinal grooves, are mainly smooth but pubescent at their rear end and sides, and are sloping downward at their posterior end.Platypus apicalis exhibits sexual dimorphism. The elytrae of males bear tooth like projections at their posterior end. The body of females is more pubescent than this of males, lack elytral teeth, and have a more rounded shape. Adult males release a strong and distinguishable odor to attract a female upon digging a breeding gallery. Females have not been found to release this scent.
Eggs are round, less than 1 mm in diameter, and have a creamy appearance. Young larvae are flat and have fleshy projections on sides. In contrast, fully grown larvae are white, cylindrical and legless with yellow coloured heads. At this stage the mandibles begin to orient downward and ridges start to appear on the top of the prothorax.
Distribution
Natural range
Platypus apicalis only occurs in New Zealand. More specifically, it occurs on the West coast of the South Island and the centre of the North Island in natural beech wood forests and in certain exotic plantations, such as these of eucalyptus.Habitat preferences
The habitat preference of this species is predominantly dead beech wood forest, including Red Beech, Silver Beech and Black beech. Platypus apicalis appear in dead tissues surrounding trees and larvae. Few fungi are related to pinhole borer closely, they benefit beetles in different ways. Ambrosia fungi provide food that they depend on. Pathogenic fungi which can infect or even kill live tree is carried by insects. The beetle has no preference for hard or soft wood as it resides inside the Beech trees and some Eucalyptus species. Platypus resides in the dead wood of the tree but when numbers grow due to sufficient breeding material, healthy trees are threatened by their invasion. They are considered pests at times to native forests but only when they threaten healthy trees. Their main pest area is the forestry plantations where they colonise and render some high-quality timber useless due to imperfections and colour change in the timber.Their nests are more likely to kill the part of living tree. The beetles occur commonly along the North Island, South Island and Chatham Island, however, has not spotted in some eastern forests such as Balmoral and Eyrewell State forests, Canterbury
Economic significance
Platypus apicalis can be a pest in high-quality timber plantations. It vectors fungi that develop into the wood, altering its color. In addition, their tunnels, which go deep into the wood, create imperfections in the finished timber, which also weakens it.Life cycle/phenology
The life cycle begins with a male adult boring a tunnel into a host tree and releasing fungal spores along the way. Fungal species, particularly ambrosia fungi, serve as the primary food for the beetle, which gives the name of the nickname to the beetle, "Ambrosia Beetles". This tunneling process usually occurs within the early summer months of November and December. Once the tunnel is several centimetres long, the insect will release an odour that acts as an attractant to female insects. If enough male beetles do this at once, it leads to so called "mass attacks" on trees where swarms of beetles attack a single host specimen. However, not like the other bark beetles that they rely on the inner tunnel, adults and larvae both will soon acquire the primary food. During the feeding stage, yeasts are likewise transmitted by bark beetles, but their precise role has not been discovered yet. Copulation occurs at the tunnel entrance and afterward the female goes into the tunnel and begins the process of making a nest. The male continues to enlarge the tunnel and remove excess frass. The tunnel is initially radial but eventually has a sharp right angle and moves towards the heartwood of a tree. Meanwhile the female lays the first batch of egg containing four to seven eggs. Following this, another branch of the tunnel is then started by the male and eventually a second egg batch is laid. The pair will feed the larvae until they reach maturity using specialized structures called mycangia, which is located on the head of the adult. At this point 8–10 months have passed since copulation.While the exact time of larval hatching is not yet certain, it is known that there is a period of two years from the time the nest is laid to the time that fully grown beetles emerge from hosts. During this time the larvae go through several stages. Initially the larva simply extend the tunnels of the parents. These extensions differ from the parents in that the tunnels are concave rather than flat. During this time, the larvae grow bigger in size and begin to take on some adult features. After a period of several months, the larva excavate pupal chambers within the tree. The larvae then enter the chambers and become pupas, intermediate insect form. Finally, when two years have passed since the egg laying, adult beetles emerge from the chambers and exit the tree. This occurs during the summer months of January to March. The average number of beetles per tree is 115. The adult beetles then go out into the forest and look for a new host tree. The lifecycle is then repeated. The average lifespan of an adult pinhole beetle is estimated to be 3–4 years.