In the Ryukyu Islands of southern Japan, we examined the ticks and mites parasitic on the body surface of sea snakes belonging to the subfamilies Hydrophiinae (Emydocephalus ijimae, Hydrophis melanocephalus and H. ornatus) and Laticaudinae (Laticauda semifasciata, L. laticauda and L. colubrina). the tick, Amblyomma nitidum, and three species of trombiculid mites were found only from Laticaudinae sea snakes. The % snakes infested by larvae, nymphs and adults of A. nitidum ranged 0-95.0%, 0-55% and 0-20.0%, respectively. Larvae and nymphs infested more intensively in warmer seasons. Frequency distributions of the number of ticks per host showed that they were not distributed randomly but clumped. Replete larvae detached from the hosts in the daytime more frequently (not examined for replete nymphs and adults). This temporal drop-off pattern results in ticks remaining in the resting sites of the hosts because the hosts usually swim at night but rest in crevices of shore rocks in the daytime, No larvae or nymphs died even when placed in artificial seawater for 24 hours in the laboratory. The infection rates of the trombiculid mites, tentatively called spp. t, w, and b in this paper, ranged 0-34.6%, 0-50.0%, and 0-25.0%, respectively. In total, 62,5% of hosts were infested by a single mite species, and 37.5% by two or three species. Similarly to the tick A. nitidum, these mites had clumped distribution patterns and diurnal drop-off rhythms after engorgement, although the latter was examined only for sp. t.

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The alarm pheromone activity was detected in the hexane rinse of Schwiebea elongata, the pool mite strain. The GC profile of the large scale extraction of mites revealed four components, and their chemical structures were identified by comparing their GC/MS spectra and GC retention times with those of authentic compounds, as follows; neral {3,7-dimethyl-(Z)-2,6-octadienal}, geranial {3,7dimethyl-(E)-2,6-octadienal}, neryl formate {3,7-dimethyl-(Z)-2,6-octadienal formate}, and n-tridecane. The alarm pheromone activity was only detected in fractions of 5% and 10% ether in hexane eluates from an SiO₂ column, and these fractions consisted only of a set of peaks, neral and geranial. Neral was the major component along with tridecane, and its percentage in citral (a mixture of neral and geranial) was differed among samples analyzed such as 94% in the small scale extraction, 90% in large scale extraction, and 79% in the active SiO₂ column eluate. The synthetic neral (purity 91% and yield 83%) was active at 10-100 ng-dose, while geranial (purity 98% and yield 32%) was hundred times less active than neral (active at ng-dose ppm), therefore neral was identified as the alarm pheromone.

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A new genus and species of pygmephorid mite belonging to the subfamily Neopygmephorinae is described and illusstrated from Japan under the name of Rhinopygmephorus rhopalomelissae. It is known only from the adult female and found attached to the body of the halictid bees, Rhopalomelissa yasumatsui Hirayama and Sphecodes scabricollis Wesmael. The new genus at a glance resembles Rackia Mahunka and Xystrorostrum Mahunka in possesing prolonged gnathosoma, but is easily distinguidshed from the latter by having much wider anterior coxisterna, apodemes 1 extending not so close to apodemes 2 posteriorly, poorly developed apodeme2, moderately thick tibiotarsus I with a strong claw and a stout process opposale to claw base, and in lacking secondary transverse apodeme.

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Homeopronematus anconai (Baker) was found on tomato plants cultivated in greenhouses in Mie and Osaka Prefectures on July and October of 2000, respectively. These are the first records of this species in Japan. In both greenhouses, the plants were heavily infested by Aculops lycopersici (Massee). After the rapid population increase of H. anconai the A. lycopersici population decreased sharply, and we speculated that H. anconai regulated the population of A. lycopersici. An adult H. anconai consumed an average of 69.3 A. lycopersici deutonymph during a 24 h experimental period in the laboratory.

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