Dissertation•
Pine Weevil Feeding Behaviour in Relation to Conifer Plant Properties
01 Jan 2014-
TL;DR: The results from a no-choice and a choice experiment indicate that the protective effect of MeJA-induced defences is, besides an overall reduction of feeding, mainly due to the reduced amount that a pine weevil can feed at one place.
Abstract: The pine weevil (Hylobius abietis (L.)) is a forest insect distributed over the Palearctic region. The adults feed on the phloem of young conifer plants causing high economic losses for the European forest industry. Still, there is very little knowledge about the structure of its feeding behaviour. Feeding behaviour can be studied in several different temporal resolutions, from differences in feeding after several weeks to diel patterns and short-term feeding, i.e. feeding patterns at the level of feeding events and meals. The aim of this thesis was to increase the knowledge about the pine weevils’ feeding patterns and the underlying behavioural mechanisms.
I studied the pine weevils’ time budget and diel behaviour as well as its short-term feeding behaviour based on video recordings. In addition, I assessed how changes in plant properties due to girdling or induction of plant defences with a chemical elicitor, methyl jasmonate (MeJA), affect the feeding pattern and preferences of the pine weevil.
Pine weevils allocated only 6 % of the time to feeding. Most of the time was spent away from the plant (70 – 80 %). Damaged plants appeared to attract the weevils because they spent more time while not feeding on damaged plants than on undamaged plants. Feeding behaviour was mostly concentrated to the second half of the dark phase, after a peak of locomotion behaviour during the first part of the dark phase. During the light phase, pine weevils mostly rested. Analysis of the short-term feeding behaviour showed that pine weevils made 4-5 meals per day, removing about 13 mm2 during about 24 minutes in each meal. Some of the feeding properties, such as how much time was spent not feeding during a meal, differed between male and female weevils. Girdling did not affect the time budget or feeding properties.
The induced plant defences with MeJA caused a reduction in meal duration. When meals consisting of only phloem, only needles or both were compared, the meal duration and the time until the initiation of a meal were more similar between the different meal contents on induced plants. In addition, the results from a no-choice and a choice experiment indicate that the protective effect of MeJA-induced defences is, besides an overall reduction of feeding, mainly due to the reduced amount that a pine weevil can feed at one place. Thus the risk of girdling and death of the plant is reduced.
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TL;DR: The field responses of Hylobius abietis (L.) and H. pinastri (Gyllenhal) to various combinations of two host monoterpenes and ethanol were studied using baited pitfall traps as mentioned in this paper.
Abstract: The field responses ofHylobius abietis (L.) andH. pinastri (Gyllenhal) (Coleoptera: Curculionidae) to various combinations of two host monoterpenes and ethanol were studied using baited pitfall traps. Both species were attracted to α-pinene, and when ethanol was added the attraction increased by 5–16 times. Limonene completely inhibited the attraction to α-pinene, even when the release rate of limonene was only about 1/50 that of α-pinene. The catches in traps with α-pinene and limonene as well as with limonene alone were similar in size to catches in empty control traps, i.e., no true repellent effect was demonstrated. When limonene was added to the combination of α-pinene and ethanol on old clear-cuttings, the catch ofH. pinastri was completely inhibited while that ofH. abietis was reduced by two thirds. On fresh clear-cuttings the inhibitory effect of limonene on the attraction to the α-pinene-ethanol combination was small or absent. Some aspects of host interactions are discussed as are practical implications regarding the choice of seedling material for planting and prospects of finding deterrents for protecting seedlings from pine weevil damage.
96 citations
TL;DR: Feeding behaviour of fifth instar tobacco hornworm caterpillars, Manduca sexta (Johansen) (Lepidoptera; Sphingidae), eating tobacco or artificial diet, is quantitatively described.
Abstract: . Feeding behaviour of fifth instar tobacco hornworm caterpillars, Manduca sexta (Johansen) (Lepidoptera; Sphingidae), eating tobacco or artificial diet, is quantitatively described. The insects grow at the same rate on both foods. There is no daily rhythm of feeding behaviour. For most insects, feeding on either food occurs in bouts with the lengths of interfeed gaps and of feeding bouts appearing to be distributed randomly. However, in many insects there is a strong correlation between the length of a feeding period and that of the preceding non-feeding period.
The proportion of time spent feeding on tobacco is much greater than on artificial diet. On tobacco, feeding periods are separated by shorter interfeed gaps than on the artificial diet, while the rate of bout initiation is similar on either food.
On both tobacco and artificial diet, the proportion of time spent feeding increases as the fifth stadium proceeds. This is due to both longer feeding bouts and shorter gaps. The rate of food acquisition within bouts does not change during the stadium.
90 citations
"Pine Weevil Feeding Behaviour in Re..." refers background in this paper
...This is a rather low frequency compared to other insect species, for example the Costa Rican weevil (5 meals in 10 hours), Colorado potato beetle (9 meals in 7 hours) and the tobacco hornworm caterpillar (2 meals per hour, based on meal and intermeal durations) (Reynolds et al., 1986; Mitchell & Low, 1994; Wright et al., 1999)....
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...Other insects have been shown to have either both a significant pre- and post-prandial correlation (Colorado potato beetle and migratory locust), a significant pre- but no post-prandial correlation (Australian sheep blowfly, tobacco hornworm caterpillar, American bird grasshopper) or a significant post- but no pre-prandial correlation (Costa Rican weevil) (Simpson, 1982; Reynolds et al., 1986; Simpson & Ludlow, 1986; Bowdan, 1988b; Bowdan, 1988a; Simpson et al., 1989; Chapman & Beerling, 1990; Mitchell & Low, 1994; Wright et al., 1999)....
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TL;DR: There was little variation in feeding patterns within the light phase, but marked changes occurred within the dark phase, feeding declining to a low level in the last 4h.
Abstract: . Feeding patterns of Locusta migratoria L. nymphs, kept under LD 12:12 at 30°C with ample food, were analysed over the first 6 days of the fifth instar. A number of differences were found between the light and dark phases. (1) More was eaten during the light than the dark, with the differences becoming progressively larger over the 6 days. (2) During light phases most insects showed an increasing tendency to feed with time since the last meal, while in the dark the probability of starting to feed remained constant. (3) There was little variation in feeding patterns within the light phase, but marked changes occurred within the dark phase, feeding declining to a low level in the last 4h. The amount eaten during a meal was regulated similarly in the light and dark, with time rather than amount eaten being of paramount importance in terminating a meal. The time when feeding started was somewhat influenced by the size of the preceding meal, but once feeding began meal size was largely independent of the preceding meal. The importance of food quality in determining the pattern of feeding is discussed.
89 citations
"Pine Weevil Feeding Behaviour in Re..." refers background in this paper
...Meals of other insects are, however, shorter ranging from about 2 to 18 minutes in duration (Simpson, 1982; Wright et al., 1999)....
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...Meals of the migratory locust, for example, rather end after a certain time than after a certain amount is ingested (Simpson, 1982)....
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...Other insects have been shown to have either both a significant pre- and post-prandial correlation (Colorado potato beetle and migratory locust), a significant pre- but no post-prandial correlation (Australian sheep blowfly, tobacco hornworm caterpillar, American bird grasshopper) or a significant post- but no pre-prandial correlation (Costa Rican weevil) (Simpson, 1982; Reynolds et al., 1986; Simpson & Ludlow, 1986; Bowdan, 1988b; Bowdan, 1988a; Simpson et al., 1989; Chapman & Beerling, 1990; Mitchell & Low, 1994; Wright et al., 1999)....
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TL;DR: Coumarin, carvone, verbenone, and limonin were consistently inhibitory to feeding by both male and female H. abietis.
Abstract: We assayed 12 plant-derived and 1 insect-produced allelochemicals-verbenone, borneol, bornyl acetate, carvone, cucurbitacin, myrcene, limonin, 4-allyanisole, α- pinene, β-pinene, limonene, and coumarin-for inhibition of feeding by the pine weevil Hylobius abietis L Scots pine twigs were treated with these compounds dissolved in ethyl acetate solvent, and adult weevils were fed for 48 h on the twigs in both choice and no-choice assays Coumarin, carvone, verbenone, and limonin were consistently inhibitory to feeding by both male and female H abietis Borneol and 4-allyanisole also demonstrated some activity as an antifeedant compound against H abietis The remainder of the compounds did not consistently inhibit weevil feeding Sex of weevils or temperature in cold storage (10 or 5°C) did not consistently affect amount of bark feeding A 48-h feeding period gave more distinct effects for active compounds than did a 24-h test
82 citations
TL;DR: Two explanations are suggested for why weevils oviposit mainly in the soil, although they are known to show stereotypic behaviour when inserting eggs in stump roots: egg predation by other arthropods or by conspecifics is avoided, and newly hatched pine weevil larvae are better than ovipositing females at locating suitable sites for larval feeding.
Abstract: Spatial and temporal distributions of eggs laid by the pine weevil Hylobius abietis (L.) (Coleoptera: Curculionidae) were studied by taking root and soil samples around pine stumps on a clear-cutting in central Sweden. In addition, first-instar larvae migrating in the soil were sampled using traps baited with host-odour. Eggs were found in the soil rather than in the bark of stump roots, which previously has been regarded as the usual oviposition site. Based on an oviposition experiment and additional field observations we conclude that eggs are laid in the bark of roots only when the surrounding material is likely to dry out. We suggest two explanations for why weevils oviposit mainly in the soil, although they are known to show stereotypic behaviour when inserting eggs in stump roots: (1) egg predation by other arthropods or by conspecifics is avoided, and (2) newly hatched pine weevil larvae are better than ovipositing females at locating suitable sites for larval feeding.
82 citations
"Pine Weevil Feeding Behaviour in Re..." refers background in this paper
...After copulation female weevils lay their eggs near the roots of recently killed or dying conifer trees, which can be found at high density in man-made clear-cuts and after storm fellings or forest fires (Nordlander et al., 1997)....
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