Insect seed predators of 24 dipterocarp species (including the genera ot Dipterocarpus, Dryobalanops and Shorea) and five species belonging to the Moraceae, Myrtaceae, Celastraceae and Sapotaceae were investigated. In a tropical lowland dipterocarp forest in Sarawak, Malaysia, these trees produces seeds irregularly by intensely during general flowering and seeding events in 1996 and/or 1998. Dipterocarp seeds were preyed on by 51 insect species (11 families), which were roughly classified into three taxonomic groups: smaller moths (Trotricidae, Pyralidae, Crambidae, Immidae, Sesiidae, and Cosmopterigidae), scolytids (Scolydae) and weevils (Curdulionidae, Apionidae, Anthribidae, and Attelabidae). Although the host-specificity of invertebrate seed predators has been assumed to be high in tropical forests, it was found that the diet ranges of some insect predators were relatively wide and overlapped one another. Most seed predators that were collected in both study years changes their diets between general flowering and seeding events. The results of cluster analyses based on the number of adult of each predator species that emerged from 100 seeds of each tree species, suggested that the dominant species was not consistent, alternating between the two years.

Abstract:The Dipterocarpaceae in South-East Asia are known for their strict mast fruiting. During fruiting, pre-dispersal seed predation by insects contributes to mortality of dipterocarp seeds. We documented the community structure of insect seed predators on 11 Shorea species in Peninsular Malaysia. Fruits were sampled sequentially throughout seed development, and 2144 and 1655 individuals of seed predator weevils and moths were collected in two mast-fruiting events. Four weevils: Nanophyes shoreae, nanophyid sp. 1, Alcidodes dipterocarpi and Alcidodes humeralis, and one moth Andrioplecta shoreae were abundant in seeds of the Shorea species. The proportion of N. shoreae to the total predators became larger in the latter fruiting event than the former while that of Alcidodes spp. became smaller. The predator species composition changed during seed development; nanophyid spp. emerged from immature fruits while Alcidodes spp. emerged from mature fruits. Andrioplecta shoreae emerged from both immature and mature fruits. The level of host specificity measured by Kullback–Leibler distance was low for most predator species in both events. Predator species composition of many Shorea was similar to each other due to the dominance of N. shoreae though it might gradually differ with the phylogenetic distance between hosts. In conclusion, predator species composition of Shorea varied during seed development within a host rather than among hosts. Intermittent synchronized fruiting by congeneric Shorea trees would be advantageous to avoid pre-dispersal insect seed predators, and contribute to their reproduction.

With reference to the data of synthetic standards, GC-EAD and GC-MS analyses of a pheromone gland extract of the soybean pod borer, Leguminivora glycinivorella (Lepidoptera: Tortricidae), resulted in three acetates [dodecyl acetate, (8E,10E)-8,10-dodecadienyl acetate (E8,E10-12:OAc), and its (8E,10Z)-isomer] at a ratio of 10 : 100 : 2.5 as a candidate of the pheromone. While the contents in the glands were low and even the titer of the major pheromonal component was ca. 0.5 ng/female, the positions of the two double bonds were confirmed by a mass spectrum of the adduct with 4-methyl-1,2,4-triazoline-3,5-dione. In a soybean field, synthetic E8,E10-12:OAc successfully attracted male moths of L. glycinivorella, and highly selective attraction was observed for E8,E10-12:OAc among the geometrical isomers of the 8,10-diene. Neither of the two minor components showed a synergistic effect on field attraction by E8,E10-12:OAc, and their roles were unclear. A binary lure of E8,E10-12:OAc and (E)-8-dodecenyl acetate (E8-12:OAc) was necessary to attract the male moths of Matsumuraeses falcana, the soybean pod worm, but E8-12:OAc strongly inhibited the attraction of L. glycinivorella by E8,E10-12:OAc, indicating that E8-12:OAc secreted by M. falcana is one of the most important factors in the reproductive isolation of these two species.

We investigated pre-dispersal seed predation by insects in a bayberry Myrica rubra Sieb. et Zucc. (Myricaceae) on Yakushima Island, Japan. To clarify the patterns of seed fate and predation, all fruit that fell into seed traps were collected to allow any insect larvae within the fruit to emerge, and the fruit were finally dissected to determine whether or not they had been attacked by insect predators. Two lepidopteran species, Thiotricha pancratiastis (Meyrick) (Gelechiidae) and Neoblastobasis spiniharpella Kuznetzov & Sinev (Blastobasidae), emerged from the fruits. Thiotricha pancratiastis is the major seed predator of M. rubra, attacking the fruits intensively during the primary stage of fruit development. Thiotricha pancratiastis had been known as a foliage feeder (leaf miner) of M. rubra, but we revealed that the insect is also an important seed predator of the bayberry.

Four olethreutine species, including two new species described herein, are associated with the fruits and seedlings of Rhizophoraceae in the Ryukyu Islands: Cryptophlebia horii Kawabe feeds on Bruguiera gymnorhiza (L.) Lam.; C. amamiana, sp. nov. feeds on Kandelia candel (L.) Druce; C. palustris, sp. nov. feeds on Rhizophora mucronata Lam.; and Eucosma coniogramma Clarke (= Eucosma okubiensis Kawabe, syn. nov, herein newly established as a junior synonym) feeds on Bruguiera gymnorhiza. Adults, larvae, and genitalia are diagnosed and illustrated for each species, and geographic distribution and information on biology are provided. In addition, we discuss Cryptophlebia species associated with mangroves worldwide, host preference, and adaptations to the mangrove environment.