Endosymbiotic bacteria that potentially influence reproduction and other fitness-related traits of their hosts are widespread in arthropods, and their appeal to researchers' interest is still increasing. In this study, the effects of removal of Cardinium infection on development, survival, and reproduction of Liposcelis bostrychophila Badonnel (Psocoptera: Liposcelididae) were investigated in the laboratory. The Cardinium-free strain was obtained by the removal of Cardinium infection by using 1% rifampicin treatment on the Cardinium-infected strain (control) for 4 wk, and no Cardinium gene product was detected in this strain throughout the experiment. The results showed that the removal of Cardinium infection had negative effects on fitness of L. bostrychophila. Compared with the control strain, the Cardinium-free strain (both in first [F1] and second [F2] generation) had a similar developmental time, reduced survivorship of immature stages, as well as reduced fecundity, which resulted in much smaller r(m) values. Using r(m) values, the fitness for Cardinium-free F1 and F2 relative to the control was calculated as 0.81 and 0.74, respectively. We concluded that the use of antibiotics combined with heat treatment might be a good control measure for L. bostrychophila.

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Endosymbiotic bacteria that potentially influence reproduction and other fitness-related traits of their hosts are widespread in arthropods, and their appeal to researchers' interest is still increasing. In this study, the effects of removal of Cardinium infection on development, survival, and reproduction of Liposcelis bostrychophila Badonnel (Psocoptera: Liposcelididae) were investigated in the laboratory. The Cardinium-free strain was obtained by the removal of Cardinium infection by using 1% rifampicin treatment on the Cardinium-infected strain (control) for 4 wk, and no Cardinium gene product was detected in this strain throughout the experiment. The results showed that the removal of Cardinium infection had negative effects on fitness of L. bostrychophila. Compared with the control strain, the Cardinium-free strain (both in first [F1] and second [F2] generation) had a similar developmental time, reduced survivorship of immature stages, as well as reduced fecundity, which resulted in much smaller r(m) values. Using r(m) values, the fitness for Cardinium-free F1 and F2 relative to the control was calculated as 0.81 and 0.74, respectively. We concluded that the use of antibiotics combined with heat treatment might be a good control measure for L. bostrychophila.

Acetylcholinesterace (AChE) is known to be the major target for organophophate and carbamate insecticides and biomolecular changes to AChE have been demonstrated to be an important mechanism for insecticide resistance in many insect species. In this study, AChE from three field populations of Liposcelis entomophila (Enderlein) (Psocoptera: Liposcelididae) was purified by affinity chromatography and subsequently characterized by its Michaelis-Menten kinetics to determine if detectable changes to AChE have occurred. Bioassays revealed that the potential resistance threat of psocids in Sichuan Province (GH) was greater than either Hubei Province (WH) or Chongqing Municipality (BB). Compared to the other two populations, the WH population possessed the highest specific activity of purified AChE. Kinetic analyses indicated that the purified AChE from GH population expressed a significantly lower affinity to the substrate and a higher catalytic activity toward acetylthiocholine iodide (ATChI) (i.e., higher K(m) and V(max) values) than BB and WH populations. In vitro studies of AChE suggest that five inhibitors (aldicarb, eserine, BW284C51, omethoate, and propoxur) all possess strong inhibitory effects with eserine having the strongest inhibitory effect against purified AChE. According to bimolecular rate constants (k(i)), the purified AChE from GH population was least sensitive to all inhibitors except for omethoate. The differences in AChE among the three populations may be partially attributed to the differences in pesticide application and control practices for psocids among the three locations.