Nucleotide sequences of a 1.6 kb long portion of the mitochondrial DNA containing the majority of the 16S rRNA gene, the tRNAval gene, and the 5' half-region of the 12S rRNA gene were determined for forty-eight individuals of nineteen Bactrocera species and one other tephritid taxon, Anastrepha ludens. Phylogenetic analyses were performed using the consistently aligned 1.5 kb long sequences, excluding seventeen portions that could not be aligned unambiguously and were aligned inconsistently among analyses using different programs and parameters. Results of phylogenetic analyses were highly congruent among distance, unweighted parsimony, and weighted parsimony methods in terms of topology of resulting trees. Bootstrap analyses supported many of the phylogenetic relationships resolved by these analyses. Although aligned sequences showed apparent biases in nucleotide content and substitutions that differed among sites within the stem/loop structure of rRNA molecules, compensation for such factors did not greatly affect the topology. The results are discussed in relation to the taxonomic positions of species used in this study and in relation to the phylogenetic and diagnostic utility of the mitochondrial rDNA fragment.

A PCR-RFLP based method of species identification was considered for 18 pest species of Bactrocera fruit flies mainly distributed in the Asia-Pacific region. A 1.6 kb portion of the mitochondrial DNA containing portions of 16S and 12S ribosomal RNA genes was determined for eight species for which the mtDNA sequences have not been studied. Comparisons of restriction patterns expected from the sequences obtained in this and previous studies revealed that all 18 species can be discriminated by PCR-RFLP using a small number of restriction enzymes. Based on the highly conserved sequences detected among the 18 species, four sets of PCR primers were designed to amplify shorter, diagnostically informative sections within the mtDNA fragment. Given the simplicity of banding patterns and the ease of amplification of DNA fragments, such sections were considered suitable for PCR-RFLP analysis. Based on the results, a scheme for the Bactrocera pest species identification was proposed. The PCR-RFLP analysis using 83 individuals revealed that the scheme correctly identified most of the 18 species except for two closely related sympatric species, Bactrocera carambolae and B. papayae; the majority of individuals of the former species showed the same banding patterns as the latter species. In addition, molecular phylogenetic analyses were performed based on the nucleotide sequences in order to examine the positioning of each species among many other species of fruit flies.

The fall webworm, Hyphantria cunea (Drury) (Lepidoptera: Arctiidae), was introduced from North America into Japan in 1945. For the first three decades after its introduction, its life cycle was bivoltine. Thereafter, its life cycle shifted to trivoltine in south-western areas of Japan. Two hypotheses have been proposed for the process that led to the shift in voltinism: one based on a single and the other on multiple independent colonizations. To test these hypotheses, mitochondrial (mt)DNA sequences were analyzed in the black-headed type of 14 Japanese, one Korean and two North American populations of H. cunea . In addition, the same regions of mtDNA were compared with the red-headed type of two North American populations. In the black-headed type, mtDNA sequences were the same in all Japanese populations and in the Korean population, but sequences of the North American populations differed from each other and from those of the other populations. These results suggest that the process of the shift in voltinism occurred originally in Japan, and that the Japanese and the Korean population of H. cunea originated from a relatively small area in North America.

SummarySeasonal changes in the percentage of macropterous individuals in natural population of Microvelia douglasi in permanent habitats were investigated in Shimane, western part of Japan. Macropterous forms of 5th instar nymphs occurred most frequently from late June to early July. However, the seasonal appearance of macropterous adults differed between habitats and years. There were significant effects of density, temperature, photoperiod and food availability on the percentage of macropters under laboratory conditions. The percentage of macropterous forms generally increased with density, but the mode of the response was modified by temperature, photoperiod and food availability. When insects were reared under long day photperiod (16L8D) with abundant food (0.5–1.0 g/container/day), the percentage of macroptery varied most among the different density treatments at the intermediate temperature (24°C) and the difference was reduced at higher temperature (28° and 32°C). Effects of temperature were small under the short day photoperiod (12L12D). Under 12L12D photoperiod sensitivity of density responses were higher at 32°C and lower at 24°C than those under 15L8D photoperiod. When the insects were supplied with food every other day, the density response became obscure. Ecological significance of environmental responses in the wing morph determination was discussed in relation to the heterogeneous environment of water surface.

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