Effects of Temperature on Development and Voltinism of Chaetodactylus krombeini (Acari: Chaetodactylidae): Implications for Climate Change Impacts.

Temperature plays an important role in the growth and development of arthropods, and thus the current trend of climate change will alter their biology and species distribution. We used Chaetodactylus krombeini (Acari: Chaetodactylidae), a cleptoparasitic mite associated with Osmia bees (Hymenoptera: Megachilidae), as a model organism to investigate how temperature affects the development and voltinism of C. krombeini in the eastern United States. The effects of temperature on the stage-specific development of C. krombeini were determined at seven constant temperatures (16.1, 20.2, 24.1, 27.5, 30.0, 32.4 and 37.8°C). Parameters for stage-specific development, such as threshold temperatures and thermal constant, were determined by using empirical models. Results of this study showed that C. krombeini eggs developed successfully to adult at all temperatures tested except 37.8°C. The nonlinear and linear empirical models were applied to describe quantitatively the relationship between temperature and development of each C. krombeini stage. The nonlinear Lactin model estimated optimal temperatures as 31.4, 32.9, 32.6 and 32.5°C for egg, larva, nymph, and egg to adult, respectively. In the linear model, the lower threshold temperatures were estimated to be 9.9, 14.7, 13.0 and 12.4°C for egg, larva, nymph, and egg to adult, respectively. The thermal constant for each stage completion were 61.5, 28.1, 64.8 and 171.1 degree days for egg, larva, nymph, and egg to adult, respectively. Under the future climate scenarios, the number of generations (i.e., voltinism) would increase more likely by 1.5 to 2.0 times by the year of 2100 according to simulation. The findings herein firstly provided comprehensive data on thermal development of C. krombeini and implications for the management of C. krombeini populations under global warming were discussed. *Scientific Article No. 3278 of the West Virginia Agricultural and Forestry Experiment Station, Morgantown, West Virginia.

The delineation of the fourth walking leg segment is temporally linked to posterior segmentation in the mite Archegozetes longisetosus (Acari: Oribatida, Trhypochthoniidae).

Acari (mites and ticks) lack external segmentation, with the only indication of segmentation being the appendages of the prosoma (chelicerae, pedipalps, and four pairs of walking legs). Acari also have a mode of development in which the formation of the fourth walking leg is suppressed until the nymphal stages, following a hexapodal larva. To determine the number of segments in the posterior body region (opisthosoma) of mites, and to also determine when the fourth walking leg segment is delineated during embryogenesis, we followed the development of segmentation in the oribatid mite Archegozetes longisetosus using time-lapse and scanning electron microscopy, as well as in situ hybridizations of the A. longisetosus orthologues of the segmentation genes engrailed and hedgehog. Our data show that A. longisetosus patterns only two opisthosomal segments, indicating a large degree of segmental fusion or loss. Also, we show that the formation of the fourth walking leg segment is temporally tied to opisthosomal segmentation, the first such observation in any arachnid.

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.