Rhynchophorus palmarum
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Palm weevil ( Rhynchophorus palmarum ) |
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| Scientific name | ||||||||||||
| Rhynchophorus palmarum | ||||||||||||
| ( Linnaeus , 1758) |
Rhynchophorus palmarum is a weevil that is common in the tropical rainforests of South America . He is a palm - pest . The larvae transmit nematodes .
features
Adults of the species reach a body length between 29 and 44 millimeters and thus belong to the large weevils. The body is elongated oval when viewed from above, it is flattened on the top, while the bottom is arched. The strong trunk at the front of the head is slightly shorter than the pronotum , it is straight, slightly curved towards the tip and widened at the base. Its front half has protruding, yellow-colored, thick hair. The antennae arise in a pit on the side of the trunk base, which is open at the bottom. The basal part of the antenna (scapus) is half as long as the proboscis and longer than the flagellum and antennae together. The antenna whip consists of six segments, the three-part club is rounded triangular. The complex eyes are closer together, but clearly separated, the top of the head between the eyes is about a fifth of the trunk width. The pronotum is longer than it is wide, flattened at the top, it can be dull or shiny and have velvety hairs or it can be bald. Its base (that is, the side towards the wing covers) is somewhat narrowed and pulled forward in the shape of a lobe towards the rear. The elytra are wider than the pronotum, each about two and a half times as long as it is wide. Their sides taper towards the back with an almost straight outer edge, at the end they are abruptly rounded, at the tip they are slightly edged. Each has six deeply incised dot stripes (and the indistinct traces of three more on the side). The brownish tinted hind wings are long, the animals can fly. Five segments are visible on the abdomen, the first short and fused to the second in the middle. The last is exposed as pygidium and is not covered by the wing covers. It is a little wider in the female than in the male
The species is usually easily distinguishable from other weevils of the genus in America, which are also harmful to palms, by the color, although this is sometimes variable (see below). A reliable distinction is made possible by the rear edge of the pronotum, which protrudes backwards in the form of a lobe in the middle and is evenly rounded in the other species.
Color variations
The beetle is usually deep black in color. As an exception, however, when viewing larger series, individuals were occasionally observed that were partly red or orange in color; these can easily be confused with Rhynchophorus ferrugineus . These color variants are not based on hybrids , as has been genetically proven.
Larvae
The larvae of the species are yellowish white in color with a dark brown head capsule. They reach body lengths between 44 and 57 millimeters. The head does not have larval eyes; whitish lightening of the head capsule can be seen in their place. The antennas are very short and two-segmented, with a tiny, conical end link. The trunk and abdomen have small yellowish-brown sclerites covered with bristles (setae). The abdomen is broadest on the fourth or fifth segment and narrowed abruptly in both directions, its segments are divided into four distinct ringlets (plicae).
distribution
The species lives in tropical America, from Argentina in the south to Mexico in the north, including the islands of Hispaniola and Cuba. Old data from the southern USA (California, Texas) are uncertain and are considered dubious.
Biology and way of life
Beetles and larvae are oligophagous herbivores on palm species . a. known coconut palm Cocos nucifera , oil palm Elaeis guineensis , Juçara palm Euterpe edulis , sago palm Metroxylon sagu , Canary Island date palm Phoenix canariensis , real date palm Phoenix dactylifera , there is also information about the grass species sugar cane Saccharum officinarum .
Female beetles lay their eggs in the tissue below the growth cone, the leaf bases or the tip of the shoot. To do this, they eat a hole with their proboscis, in which eggs are then laid, but they also like to take advantage of existing holes or cuts. In each hole a few eggs are laid next to one another but without direct contact, each female can lay around 250 eggs. After about four days, the larvae hatch and dig burrows into the tissue, preferring the soft and nutrient-rich tissue of the shoot tip (the “ palm heart ”). After about 55 to 70 days in Brazil, in northern Mexico only after 120 to 180 days, the larvae pupate in an eroded cavity inside the palm. To do this, they build a cocoon out of plant fibers. The new adults hatch after about 50 days of rest. The adult beetles have a lifespan of around one to two months. The beetles occur equally in all seasons.
Harmful effect
The larva of the species damages the palm tree's growth cone, which it can cause to die. However, the harmful effect is even stronger as a vector of the nematode species Bursaphelenchus cocophilus (Cobb), which causes the so-called "Red Ring Disease" (Rotring Disease) in palms. According to research, around half of the beetles carry the nematode, either internally or externally. The most important and eponymous symptom of the disease is a brick-red, ring-shaped discoloration inside the trunk and other tissues, which typically reaches about 5 centimeters wide on older trees. If the infestation is more severe, the leaves turn yellow, later the entire crown dies. The disease is considered to be one of the most significant coconut palm diseases in tropical America and the Caribbean.
Use of the larvae as food
In Peru the larva is called Suri and is valued as an edible insect . Suri is considered a delicacy. The larvae are collected from dead palm trunks (e.g. the Buriti palm ). See also Rhynchophorus ferrugineus in Papua New Guinea , whose larvae , known as sago worms , also serve as a source of protein.
literature
- H. Books: Tropical crops: origin, evolution and domestication , ISBN 978-3-662-13238-8
- Heinrich Schmutterer: Tropical insects , ISBN 978-3-89432-877-1
Individual evidence
- ↑ H. Books: Tropical Crop Plants: Origin, Evolution and Domestication [1]
- ↑ a b c d Anuwat Wattanapongsiri (1966): A revision of the genera Rhynchophorus and Dynamis (Coleoptera: Curculionidae). Thesis, Oregon State University.
- ↑ a b c Michael C. Thomas: Giant Palm Weevils of the Genus Rhynchophorus (Coleoptera: Curculionidae) and Their Threat to Florida Palms. Pest Alert, Florida Department of Agriculture and Consumer Services, Division of Plant Industry DACS-P-01682. February 2010.
- ↑ a b Bernhard Löhr, Aymer Andrés Vásquez-Ordóñez, Luis Augusto Becerra Lopez-Lavalle (2015): Rhynchophorus palmarum in Disguise: Undescribed Polymorphism in the “Black” Palm Weevil. PLoS One 2015 10 (12): e0143210. doi : 10.1371 / journal.pone.0143210
- ^ Reginald Griffith (1987): Red Ring Disease of Coconut Palm. Plant Disease 71 (2): 193-196.
- ↑ Palm worm Rhynchophorus palmarum traditional food in Amazonas Venezuela - Nutritional composition small scale production and tourist palatability [2]
- ↑ Süddeutsche Zeitung Travel Tips Peru & Bolivia House Recipe [3]
- ↑ Diploma thesis Martina Park: Investigations into the discrepancy between food diversity and nutritional diversity in Shuar communities in the Nangaritza Valley, South Ecuador. [4]
