Eggs and young larvae of the endangered brackish water damselfly, Mortonagrion hirosei, were reared under various concentration of saline water, comparing with those of Ischnura senegalensis, I. asiatica and M. selenion, all of which inhabited the abandoned rice paddy fields near the habitat of M. hirosei, reed community. The hatchability of each species under high concentration of saline was low, and 20‰ of saline water did not allow to hatch in I. asiatica and M. selenion. The mortality of young larvae of each species was also increased with the concentration of saline, and 15‰ of saline water was harmful to survive for both I. asiatica and M. selenion. Saline seemed to affect the moulting of the young larvae. On the other hand, M. hirosei and I. senegalensis had similar saline tolerance at egg and young larval stages. Both species were considered to survive under brackish water, and then M. hirosei might be a prey of I. senegalensis when they co-existed in the fields. The conservation strategy for M. hirosei was discussed in view point of the artificially established reed community for the larval habitat.

View full abstract

Narathura bazalus (Hewitson) which had been known in western and southern Japan, has been found in the Kanto district in recent years. We investigated the seasonal development and the parasitoids and accompanying ants of immatures of N. bazalus in northern Kanto in 2002-2003. The larval food, i.e., new leaves of Lithocarpus edulis, was produced continually on host trees from early spring to late autumn because branches were pruned frequently. N. bazalus produced 3 or 4 generations per year in Tsukuba city, Ibaraki Prefecture. A few eggs of the 1st generation were discovered in early April. The peaks of the number of eggs in the 2nd, 3rd and 4th generations were late June-early July, late August and mid-September, respectively. Larvae passed 5 instar stages before pupation. A few species of parasitic wasps emerged from eggs and pupae, but the rate of parasitism was very low. Seven species of ants were accompanying larvae and/or pupae.

View full abstract

The nesting biology of Andrena (Plastandrena) japonica (Smith) was studied at a personal garden of about 100m² in Matsue (35°29'N), southwestern Honshu, Japan, in 1984. This species is bivoltine. Therefore, A. (P.) fukaii Cockerell becomes a junior synonym, as the spring morph of A. japonica. The biological features of A. japonica are as follows: 1) The nesting period of the overwintering generation (G₀) and the first generation (G₁) is nearly the same, about 1.5 months, the former lasts from the middle of April to early June, and the latter from the middle of June to late July. 2) Immatures of G₀ develop into adults by the middle of October. 3) The nest density at maximum reaches up to 300 nests/m² (total in the garden was 4,736 nests) in G₀, and 252 nests/m² (5,688 nests) in G₁. 4) The nest type is linear-branched. One or two lateral burrows connect to the main burrow, each containing 1-7 serially arranged provisioned cells. 5) The number of cells in completed nests is 6.3±0.9 (n=3) in G₀, and 7.0±1.4 (n=5) in G₁. 6) The mean number of foraging trips performed per day is 2.7, spending 54 minutes/trip in G₀, and 3.4, for 42 minutes/trip in G₁. 7) One pollen loaf for both males and females was made by respectively 4 and 6 foraging trips. These values, mentioned in 6) and 7), suggest that one bee makes one cell every two days under favorable conditions. 8) Nesting duration is 31.7±3.9 days (n=13) in G₀. 9) Some bees (4/31) rarely make two nests. 10) The female ratio (females/(females+males)) is around 0.75 in both generations, indicating that the sex ratio is female-biased. 11) As natural enemies of A. japonica, the bee, Nomada rengino Tsuneki, and flies, Myopa buccata (L.), M. testacea Krober, and Bombylius sp. were found in nests.

View full abstract

The impact of the ant Lasius niger attending the cotton aphid, Aphis gossypii, on the number of emerging adults of this aphid's primary parasitoid, Lysiphlebus japonicus, and its hyperparasitoids in the presence of predators was assessed experimentally at a no-pesticide mandarin grove. Aphid colonies were artificially initiated on young citrus shoots in spring. L. japonicus females were observed foraging more frequently in ant-attended aphid colonies than in colonies where ants were excluded using tanglefoot. They were often attacked by ants, but oviposited successfully by avoiding encounters with approaching ants. In ant-excluded colonies, L. japonicus parasitized a small number of aphids, with most of them being subject to intraguild predation mainly by the coccinellid Harmonia axyridis. Attending ants drove away large predators, including H. axyridis, from aphid colonies through aggressive behavior, so that the aphid numbers were consistently greater in ant-attended colonies. Ants disregarded parasitized aphids, thereby incidentally protecting them against large predators. Consequently, L. japonicus-mummies were abundant in ant-attended colonies, but scarce in ant-excluded colonies. In addition, significantly more adults of L. japonicus and hyperparasitoids emerged in ant-attended colonies. Many larvae of a small coccinellid, Scymnus posticalis, foraged in ant-attended colonies, but were ignored by ants. The number of mummies in ant-attended colonies was reduced when S. posticalis larvae were abundant, but the difference was insignificant. Ant-exclusion after mummy formation revealed that ants reduced intraguild predation and hyperparasitism on immature L. japonicus within mummies. Thus, L. niger attending A. gossypii increases the number of emerging adults of this aphid's primary parasitoid and hyperparasitoids by repelling large intraguild predators, although ants do disturb ovipositing parasitoids.

View full abstract

Part 1: Generic characteristics, phylogenetic relationships and a brief review of the biology of the genus Dipogon are presented. Three species of the conspersus group of the subgenus Deuteragenia occurring in Japan are treated: Dipogon (Deuteragenia) conspersus is redescribed, and two new species, D. (Deu.) sperconsus and D. (Deu.) inconspersus, are described. Part 2: Two species-groups of the subgenus Deuteragenia, genus Dipogon, occurring in Japan are treated. In the Dipogon vechti species-group, D. vechti and D. romankovae are recorded from Japan and redescribed, and D. albithrix sp. nov. is described. In the D. granulifrons species-group, D. granulifrons sp. nov. and D. carychroceraeus sp. nov. are described. Part 3: Three species belonging to two species-groups of the subgenus Deuteragenia, genus Dipogon, occurring in Japan are revised: Dipogon immarginatus (D. immarginatus group), D. bifasciatus and D. nipponicus (D. bifasciatus group). Detailed descriptions and illustrations of their characteristics, including those of the genitalia, are provided for all species. Keys to five species-groups in Japan, as well as all species treated in this series, are presented.

View full abstract