Ikuo Kandori

Diverse visitors with various pollinator importance and temporal change in the important pollinators of Geranium thunbergii (Geraniaceae)

Assessing pollinator importance of each floral visitor to a plant species is a key to understanding plant–pollinator interaction. The present study examined visitation frequency, pollination efficiency, and pollinator importance of the full range of floral visitors to Geranium thunbergii natural population, by measuring seed-set. During 2 years of observations, the flowers were visited by at least 45 insect species belonging to four orders. Among the main 22 visitor species, 11 species belonging to three orders (Hymenoptera, Diptera, and Lepidoptera) acted as the efficient pollinators. In both years, Hymenoptera, especially bees, was the most important pollinator to G. thunbergii. Thus, the flowers could be considered as bee-pollinated. However, the most important species were not constant between years. The study also documented that the efficient pollinators have larger body sizes. The dish-shaped floral morphology, taxonomically diverse pollinators, and temporal change in the most important pollinators indicate that G. thunbergii–pollinator interaction is a rather generalized system. The results suggest that casual observations of visitation, or even precise measurement of pollinator importance in a single season is insufficient to identify important pollinators.

Interspecific and intersexual learning rate differences in four butterfly species.

SUMMARY Learning plays an important role in food acquisition for a wide range of insects and has been demonstrated to be essential during flower foraging in taxa such as bees, parasitoid wasps, butterflies and moths. However, little attention has been focused on differences in floral cue learning abilities among species and sexes. We examined the associative learning of flower colour with nectar in four butterfly species: Idea leuconoe, Argyreus hyperbius, Pieris rapae and Lycaena phlaeas. All butterflies that were trained learned the flower colours associated with food. The flower colour learning rates were significantly higher in I. leuconoe and A. hyperbius than in P. rapae and L. phlaeas. Among the four species examined, the larger and longer-lived species exhibited higher learning rates. Furthermore, female butterflies showed a significantly higher learning rate than males. This study provides the first evidence that learning abilities related to floral cues differ among butterfly species. The adaptive significance of superior learning abilities in the larger and longer-lived butterfly species and in females is discussed.

Reward and non-reward learning of flower colours in the butterfly Byasa alcinous (Lepidoptera: Papilionidae)

Learning plays an important role in food acquisition for a wide range of insects. To increase their foraging efficiency, flower-visiting insects may learn to associate floral cues with the presence (so-called reward learning) or the absence (so-called non-reward learning) of a reward. Reward learning whilst foraging for flowers has been demonstrated in many insect taxa, whilst non-reward learning in flower-visiting insects has been demonstrated only in honeybees, bumblebees and hawkmoths. This study examined both reward and non-reward learning abilities in the butterfly Byasa alcinous whilst foraging among artificial flowers of different colours. This butterfly showed both types of learning, although butterflies of both sexes learned faster via reward learning. In addition, females learned via reward learning faster than males. To the best of our knowledge, these are the first empirical data on the learning speed of both reward and non-reward learning in insects. We discuss the adaptive significance of a lower learning speed for non-reward learning when foraging on flowers.

Comparison of Foraging Activity between Mason Bee Osmia orientalis (Hymenoptera: Megachilidae) and Honybees for Wild Raspberry Rubus hirsutus (Rosales: Rosaceae)

ABSTRACT: 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.

Strongly biased sex ratio in cuckoo wasp Chrysura hirsuta (Hymenoptera: Chrysididae), a parasitoid of the mason bee Osmia orientalis

We examined the rate of parasitism and sex ratio of the cuckoo wasp Chrysura hirsuta (Gerstaecker) (Hymenoptera: Chrysididae) that emerged from nests of the mason bee Osmia orientalis Benoist (Hymenoptera: Megachilidae) in Nara, Japan. Nests of O. orientalis were found in empty shells of two snail species, Satsuma japonica (Pfeiffer) and Euhadra amaliae (Kobelt). The percentage of parasitism by cuckoo wasps per all collected cocoons tended to be high (20–50%) even though interannual variation and the average number of cocoons per nest did not differ across snail shell species within each year. Our results from three years of observation, combined with previous reports, showed that the adult sex ratio of C. hirsuta was strongly female‐biased, which suggests that the species reproduces by thelytokous parthenogenesis.

Long Frontal Projections Help Battus philenor (Lepidoptera: Papilionidae) Larvae Find Host Plants

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.

The choosing of sleeping position in the overnight aggregation by the solitary bees Amegilla florea urens in Iriomote Island of Japan

In addition to the process of joining the sleeping aggregation, the choice of sleeping position is an important night-time behaviour of small diurnal insects because of the increased risk for predator attacks as well as bad weather. The aggregation behaviour of the solitary bee Amegilla florea urens was investigated to elucidate the choice of sleeping position on substrates. Male and female constructed single-sex aggregations on hanging leaves during May and June, respectively. Most individuals tended to form aggregations with other individuals while few individuals slept alone. During the aggregation forming, both the number of individuals that tried to join the aggregation and the completion time of aggregation increased with the number of sleeping individuals, whereas the success rate of joining was unaffected. The sleeping positions of subsequent arrivals on the substrates were higher than those of the first arrivals in female aggregations. Therefore, the first female to arrive tended to be located near the bottom of a hanging substrate. Dissecting sleeping females showed that they contained mature oocytes, indicating that sexually mature individuals formed aggregations. In male aggregations, however, we could not find a clear relationship between the position on substrates and the arrival sequence. We suggest that the purpose for sleeping in aggregations might be a dilution effect for nocturnal predation and that the females that finished both nesting and foraging quickly could choose the optimal positions in the aggregation when they arrived on the sleeping substrates.