Spectrum-specific UV egg damage and dispersal responses in the phytoseiid predatory mite Neoseiulus californicus (Acari: Phytoseiidae).

Solar ultraviolet-B (UVB) radiation is deleterious to plant-dwelling mites. Neoseiulus californicus (McGregor) is a predominant predator of agriculturally important pest species of spider mite. However, phytoseiid mites are more vulnerable to UVB radiation than spider mites. Thus, the UVB radiation may influence decision making in foraging phytoseiid mites whether disperse or not. We tested the difference in impact and behavioral response among wavelengths of monochromatic UV radiation using a spectroscopic light source in N. californicus in the laboratory. We also examined whether the behavioral responses of N. californicus females to UV radiation varied based on the presence of prey (Tetranychus urticae Koch) eggs and residues (webs and excreta of T. urticae: foraging cue). The impact of UV radiation on the N. californicus egg hatchability varied drastically between wavelengths of ≤300 nm (0%) and ≥310 nm (100%). The N. californicus females escaped from UV radiation more quickly when they were irradiated with UV at shorter wavelength. Presence of T. urticae eggs had no effects arresting the escape of phytoseiid mites. In contrast, prey residues (including eggs) markedly detained N. californicus females from escaping under UV irradiation at ≥310 nm. However, N. californicus females quickly escaped when irradiated with UV at harmful 300 nm wavelength, regardless of prey cues. This indicates that the eyeless phytoseiid mite is capable of perceiving UV radiation, and whether escape or not is determined on the basis of harmful/harmless UV wavelength and presence/absence of foraging cues.

The effect of temperature on the viability of Demodex folliculorum and Demodex brevis.

Demodex folliculorum and Demodex brevis are obligatory parasites of the pilosebaceous unit in humans and are cosmopolitan in terms of their distribution. This study was conducted to explore the effect of temperature on the viability of D. folliculorum and D. brevis. Both types of parasites were collected with the cellophane tape method, then randomly grouped and placed into separate moist cabinets. They were divided into 15 groups and exposed to experimental temperatures ranging from -15 degrees C to 60 degrees C. Curve diagrams and scatter plots on the relationship between temperature and the corresponding survival time were drawn and analyzed. It is demonstrated that temperature has a tremendous influence on the viability of D. folliculorum and D. brevis. Survival time and temperature are inversely correlated in the temperature range of 5-37 degrees C. Both D. folliculorum and D. brevis can survive better at low temperatures than at high temperatures. The most suitable maintenance temperature is 5 degrees C, and the optimal temperature for D. folliculorum and D. brevis to develop in vitro is 16-20 degrees C. Temperatures below 0 degrees C and above 37 degrees C are harmful to the mites. The lethal temperature is 54 degrees C, and the effective temperature that kills Demodex mites is 58 degrees C.

Exigências térmicas e tabela de vida de fertilidade de Phytoseiulus macropilis (Banks) (Acari: Phytoseiidae) / Thermal requirements and fertility life table of Phytoseiulus macropilis (Banks) (Acari: Phytoseiidae)

Estudaram-se as exigências térmicas de Phytoseiulus macropilis (Banks) alimentado com Tetranychus urticae Koch em cinco temperaturas constantes (18, 20, 23, 26 e 30°C), e determinou-se o efeito de três temperaturas constantes (20, 23 e 26°C) sobre os parâmetros biológicos da fase adulta do ácaro. Os dados foram utilizados para construir tabelas de vida de fertilidade. Os estágios de ovo, larva, protoninfa, deutoninfa e período de ovo-adulto apresentaram temperaturas base de 12,6; 13,1; 11,6; 13,4 e 12,7°C, respectivamente, e constantes térmicas de 26,65; 10,27; 16,04; 13,31 e 66,04 GD, respectivamente. A duração média da geração (T) variou de 24,3 a 18,5 dias entre as temperaturas de 20°C e 26°C. A maior taxa líquida de reprodução (R0 = 35,3) e a maior capacidade intrínseca de aumento populacional (r m = 0,19) foram obtidas a 23°C. A maior fecundidade foi verificada a 26°C.

Thermal requirements of Phytoseiulus macropilis (Banks) fed with Tetranychus urticae Koch at five constant temperatures (18, 20, 23, 26 and 30°C), and the effect of three constant temperatures (20, 23 and 26°C) on the adult stage were studied. The data were used to produce the fertility life tables. The stages of egg, larva, protonymph, deutonymph and adult egg corresponded to the temperature thresholds of 12.6, 13.1, 11.6, 13.4 and 12.7°C, respectively, and thermal constants of 26.65, 10.27, 16.04, 13.31 and 66.04 DD, respectively. The average duration of a generation (T) varied from 24.3 to 18.5 days at the temperatures from 20°C to 26°C. The highest net reproduction (R0 = 35,3) and the intrinsic rate of increase (r m = 0,19) were obtained at 23°C. The highest fecundity rate was registered at 26°C.

The behavioral responses by larvae of the water mite Unionicola foili (Acari: Unionicolidae) to gravity, light and host chemicals: adaptations for transmission success?

The life cycle of the water mite Unionicola foili includes larvae that parasitize chironomid dipterans, and nymphs and adults that occur in association with the freshwater mussel Utterbackia imbecillis. The georesponses and photoresponses of larval U. foili in the presence of chemical substances from chironomids and mussels both prior to (= pre-chironomid larvae) and after their parasitism with chironomids (= post-chironomid larvae) were examined in the laboratory. The responses of larval U. foili to light and gravity changed during larval ontogeny and varied depending on the chemistry of the medium in which they were examined. Pre-chironomid larvae preferentially responded to water modified by chironomids given that negative phototaxis and positive georesponses were elicited only in the presence of water that had been modified by these hosts. Post-chironomid larvae exhibited host-induced negative phototaxis only in the presence of mussel-modified water. Post-chironomid larvae were consistently geopositive when exposed to water modified by mussels or chironomids. The pattern of responses exhibited by larval U. foili to light and gravity are interpreted as adaptations for locating potential hosts in the field.