Using wild pollinators to pollinate crops without introducing human-managed pollinators is cost-effective and friendly to native ecosystems. To maintain stable, good-quality yields in crops that ...mainly use wild pollinators, it is essential to determine which flower visitors are important pollinators and their degree of importance. In this study, we observed flower-visiting insects for 5 years in outdoor cultivated strawberries surrounded by a semi-natural environment in central Japan. We estimated the pollination effectiveness and efficiency of the 10 main flower-visiting insect taxa on strawberries by examining the relationship between the number of visits per flower and subsequent achene fertilization rates per berry. Finally, the pollinator importance (%) to the total pollination service was estimated for each of the 10 main taxa and for all others. Among the 10 main insect taxa, 6 were effective pollinators, i.e., they significantly increased achene fertilization rates by increasing their number of visits to a flower. Considering the 5-year mean, these six taxa accounted for the top six important pollinators. Andrena (subgenus Micrandrena) spp. were the most important and three other bee taxa, including Apis mellifera and Ceratina spp., were the next most important pollinators; one fly and one butterfly species were also important pollinators. This indicates that strawberry pollinators were diverse in the study area. The flower-visit frequency and importance of many pollinators fluctuated from year to year, implying that various pollinators pollinate strawberry flowers each year, and in field surveys of crop-pollinator communities multiyear investigations are needed to identify important pollinators and to estimate their importance. To the best of our knowledge, this is the first attempt to quantify the proportional importance of each pollinator to the total pollination service for a crop.
Animals sometimes have prominent projections on or near their heads serving diverse functions such as male combat, mate attraction, digging, capturing prey, sensing or defence against predators. Some ...butterfly larvae possess a pair of long frontal projections; however, the function of those projections is not well known. Hestina japonica butterfly larvae have a pair of long hard projections on their heads (i.e., horns). Here we hypothesized that they use these horns to protect themselves from natural enemies (i.e., predators and parasitoids). Field surveys revealed that the primary natural enemies of H. japonica larvae were Polistes wasps. Cage experiments revealed that larvae with horns intact and larvae with horns removed and fitted with horns of other individuals succeeded in defending themselves against attacks of Polistes wasps significantly more often than larvae with horns removed. We discuss that the horns counter the paper wasps' hunting strategy of first biting the larvae's 'necks' and note that horns evolved repeatedly only within the Nymphalidae in a phylogeny of the Lepidoptera. This is the first demonstration that arthropods use head projections for physical defence against predators.
The impact of invasive alien species on native species is of increasing global concern. Invasive plants have various negative effects on natives through competition; however, relatively little is ...known about competition for pollination. The relationship between Japanese native dandelions (Taraxacum spp.) and invasive congeners may be a typical case of such an interaction. For example, native dandelions are being replaced by invasive congeners, especially in urban and suburban areas of Japan. To explain this phenomenon, we hypothesized that when natives are mixed with attractive invasives, natives may suffer from reduced seed set because invasives deprive natives of pollinators or because pollinators frequently move between species, resulting in interspecific pollen transfer. To test this hypothesis, we studied the effect of the invasive dandelion T officinale on the pollination and seed set of the native T. japonicum using artificial arrays of monospecific and mixed-species plots as well as natural populations. Taraxacum officinale attracted more pollinator visits, perhaps because it produced more nectar than T. japonicum. The number of pollinator visits to T. japonicum was reduced when the congeners were grown together, and pollinators moved frequently between the two species. The proportion of seed set for T. japonicum was reduced in the presence of T. officinale in both artificial arrays and natural populations. These results support our hypothesis that interspecific competition for pollination plays an important role in the recent replacement of native dandelions by invasive congeners in Japan. Because invasive dandelions are apomicts, negative effects are incurred only by sexual natives. Thus, this system can be recognized as a rare case of interspecific interaction through pollination.
To develop an augmentative biological control programme for
Bemisia tabaci
(Gennadius) (Hemiptera: Aleyrodidae) and
Thrips palmi
Karny (Thysanoptera: Thripidae) using
Nesidiocoris tenuis
(Reuter) ...(Hemiptera: Miridae), we studied the life history traits of a Japanese strain of
N. tenuis
reared on
B. tabaci
and
T. palmi
in controlled environments. The lower developmental threshold during the nymphal period was far higher than those estimated for Spanish, Moroccan, and Iranian strains, indicating that the Japanese strain is better adapted to higher temperatures than the other three strains tested. The intrinsic rate of increase
r
m
was highest at 30 °C and lowest at 20 °C. The
r
m
value for individuals reared on
T. palmi
at 25 °C was lower than that for individuals reared on
B. tabaci
at the same temperature. Implications of these results for the biological control of
B. tabaci
and
T. palmi
in greenhouses are discussed.
Animals sometimes develop conspicuous projections on or near their heads as, e.g., weaponry, burrowing or digging tools, and probes to search for resources. The frontal projections that insects ...generally use to locate and assess resources are segmented appendages, including antennae, maxillary palps, and labial palps. There is no evidence to date that arthropods, including insects, use projections other than true segmental appendages to locate food. In this regard, it is noteworthy that some butterfly larvae possess a pair of long antenna-like projections on or near their heads. To date, the function of these projections has not been established. Larvae of pipevine swallowtail butterflies Battus philenor (Papilionidae) have a pair of long frontal fleshy projections that, like insect antennae generally, can be actively moved. In this study, we evaluated the possible function of this pair of long moveable frontal projections. In laboratory assays, both frontal projections and lateral ocelli were shown to increase the frequency with which search larvae found plants. The frontal projections increased finding of host and non-host plants equally, suggesting that frontal projections do not detect host-specific chemical cues. Detailed SEM study showed that putative mechanosensillae are distributed all around the frontal as well as other projections. Taken together, our findings suggest that the frontal projections and associated mechanosensillae act as vertical object detectors to obtain tactile information that, together with visual information from lateral ocelli and presumably chemical information from antennae and mouthparts, help larvae to find host plants. Field observations indicate that host plants are small and scattered in southern Arizona locations. Larvae must therefore find multiple host plants to complete development and face significant challenges in doing so. The frontal projections may thus be an adaptation for finding a scarce resource before starving to death. This is the first evidence that arthropods use projections other than true segmental appendages such as antennae, mouthparts and legs, to locate food resources.
Nesidiocoris tenuis
(Reuter) (Hemiptera: Miridae) is a zoophytophagous mirid that can also feed on the plants upon which its prey lives. It is a generalist predator feeding on whiteflies, thrips, ...aphids, and other pests. The use of alternative plants as banker plants is recommended to aid the establishment of released natural enemies in greenhouses. If
N
.
tenuis
populations reproduce only on banker plants, the use of alternative hosts or prey to rear
N. tenuis
will be unnecessary, which makes the banker plant system easier to manage.
Verbena
×
hybrida
Voss (Lamiales: Verbenaceae) cv. Tapien and
Scaevola aemula
R. Br. (Asterales: Goodeniaceae) are recommended banker plants in Japan. This study examined the development, survival, and oviposition of
N
.
tenuis
on these two plant species in the laboratory, with and without flowers.
N
.
tenuis
performed similarly on both plants. The intrinsic rate of increase was slightly higher on
Verbena
×
hybrida
than
S
.
aemula
. The sugars in water samples collected from flowers of both plant species were analyzed using high-performance liquid chromatography. Fructose and glucose were detected in
Verbena
×
hybrida
, while fructose, glucose, and sucrose were detected in
S
.
aemula
. The total amount of sugars per ten flowers was much higher in
Verbena
×
hybrida
. These sugars, possibly derived from floral nectars, are considered as nutrients promoting the reproduction of
N
.
tenuis
, in addition to pollen.
Verbena
×
hybrida
and
S
.
aemula
both facilitate
N
.
tenuis
reproduction and can be used as banker plants.
The zoophytophagous mirid predator
Nesidiocoris tenuis
(Reuter) (Hemiptera: Miridae) is used in the augmentative biological control of
Thrips palmi
Karny (Thysanoptera: Thripidae), a fruit and ...vegetable pest in protected culture in Japan.
N. tenuis
can be maintained on certain plants without arthropod prey. Although such plant species may be useful as banker plants, their attractiveness to
N. tenuis
is underresearched. We investigated the behavioral responses of
N. tenuis
to (1) uninfested and conspecific-infested banker plants,
Verbena
×
hybrida
(verbena),
Scaevola aemula
(scaevola),
Cleome hassleriana
(cleome), and
Lobularia maritima
(sweet alyssum) and (2) conspecific-infested banker plants and
T. palmi
-infested eggplants, using a Y-tube olfactometer. Female
N. tenuis
preferred the volatiles emitted by (1) uninfested verbena over clean air but showed no preference for those emitted by the other uninfested banker plants, and (2) conspecific-infested verbena over clean air but showed no preference for those emitted by conspecific-infested scaevola over clean air. The attractiveness of the volatiles of
T. palmi
-infested eggplants for
N. tenuis
was not significantly different from those of
N. tenuis
-infested verbena and scaevola. As both uninfested and conspecific-infested verbena attracted female
N. tenuis
, this species is a promising banker plant. Chemical analyses and principal coordinate analyses of the volatiles from the headspaces of uninfested and
N. tenuis
-infested verbena and scaevola showed that 1-octen-3-ol, (
E
)-β-caryophyllene, and (
E
)-4,8-dimethyl-1,3,7-nonatriene distinguished these plant species and are candidate volatile
N. tenuis
attractants.
Foraging traits of honeybees and Osmia bees have previously been compared in crop production. However, less is known about the difference in foraging traits during visits to wild flowers. We ...conducted experiments to clarify the foraging behavior of Osmia orientalis visiting wild raspberry Rubus hirsutus and compared it with two solitary bees (Micrandrena spp. and Ceratina flavipes) and two honeybee species (Apis mellifera and A. cerana japonica). The average number of visiting individuals of O. orientalis was greater than that of honeybees. For O. orientalis, the handling time and the number of flowers that an individual visited were no different from those of honeybees. However, more O. orientalis individuals than honeybees collected pollen. The study suggests that the foraging activity of O. orientalis for wild raspberry would be as high as that of honeybees.
Learning plays an important role in food acquisition in a wide range of insect species. However, few studies have explored differences in the ability to learn floral cues among pollinator species ...across insect orders. In this study, we examined associative learning of flower color with nectar rewards for females or female workers in two bee species (an eusocial bumblebee Bombus ignitus and a solitary mason bee Osmia orientalis) and two hoverfly species (Eristalis cerealis and E. tenax). Prior data for females of four butterfly species (Idea leuconoe, Argyreus hyperbius, Pieris rapae, and Lycaena phlaeas) were included for analyses of flower color‐learning rate in a total of eight species of three insect orders (Hymenoptera, Diptera, and Lepidoptera). All eight species learned flower colors associated with food. Flower color‐learning rate was highest in B. ignitus, followed by the two larger butterflies (I. leuconoe and A. hyperbius), the two smaller butterflies (P. rapae and L. phlaeas), and the remaining species (E. cerealis, E. tenax, and O. orientalis). These results represent the first evidence that the ability to learn floral cues differs among flower‐visiting insects of different orders. We discuss the adaptive significance of superior learning abilities in bumblebees and butterflies and that of inferior learning abilities in the two hoverflies and mason bees.
In this study, we examined associative learning of flower color with nectar rewards in two bee species (Bombus ignitus and Osmia orientalis), two hoverfly species (Eristalis cerealis and E. tenax) and four butterfly species (Idea leuconoe, Argyreus hyperbius, Pieris rapae, and Lycaena phlaeas). Flower color‐learning rate was highest in B. ignitus, followed by the two larger butterflies (I. leuconoe and A. hyperbius), the two smaller butterflies (P. rapae and L. phlaeas), and the remaining species (E. cerealis, E. tenax, and O. orientalis).
The indigenous endoparasitic koinobiont Dacnusa nipponica is considered a potential parasitoid of the exotic leaf-mining fly Liriomyza trifolii in Japan. However, this endoparasitoid rarely emerges ...from L. trifolii pupae collected in the field. To determine why, we compared the parasitization, growth, and development of D. nipponica and the introduced parasitoid, D. sibirica, on L. trifolii hosts. When each parasitoid was only provided L. trifolii as a host, D. nipponica exhibited a slightly lower parasitization rate (confirmed by dissecting hosts, 34.7%) than D. sibirica (42.2%). However, the survival rate of parasitoid progeny within hosts was much lower for D. nipponica (7.2%) than for D. sibirica (69.4%), which was caused by the developmental arrest or death of D. nipponica at the prepupal stage within L. trifolii pupae. Furthermore, the survival rate of parasitoid progeny within hosts was much lower for D. nipponica (13.3%) than for D. sibirica (82.6%) when both parasitoids were allowed to parasitize artificially dwarfed individuals of Chromatomyia horticola, which is naturally much larger than L. trifolii and is a suitable host for both parasitoid species. The survival rate of progeny was lower for both D. nipponica and D. sibirica within smaller individuals of dwarfed C. horticola pupae. These results suggest that L. trifolii is large enough to host the growth and development of D. sibirica but too small for successful parasitization by D. nipponica.
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