A β-actin gene, Libβ-actin1, from the psocid, Liposcelis bostrychophila, was isolated, sequenced, and expressed inEscherichia coli. The cDNA sequence was 1 281 bp in length and contained an open reading frame of 1 131 bp encoding376 amino acids with a predicted molecular weight of 41.82 kDa. According to a BlastN search, the coding region sharedthe highest identity (97%) with Pediculus humanus actin 5C, while the deduced amino acid sequence was completelyidentical to a mutant of Drosophila melanogaster actin 5C. Comparison of the nucleotide and deduced amino acidsequences confirmed the high similarity between Libβ-actin1 and homologs in other insect species. The 3´ untranslatedregion (3´ UTR) of the Libβ-actin1 mRNA had a high A+U content (approximately 75%) and contained three repeats of theAUUUUUA and AUUUA motifs, which may play a role in regulating mRNA decay. The expression of Libβ-actin1 wasfurther analyzed in insecticide induced and control psocids. The results indicated that there was no significant differencein expression of Libβ-actin1 between the induced and control groups, suggesting that Libβ-actin1 may be an appropriateinternal control for the gene expression profiling in this insect. Furthermore, Libβ-actin1 was also heterologouslyexpressed in Escherichia coli, which provided a basis to investigate the physiological functions of actin genes in thepsocid.

The beet armyworm, Spodoptera exigua (Lepidoptera: Noctuidae), is an economically important pest of crops worldwide,attacking plants from over 20 families including trans-continental agricultural cotton, corn and citrus crops. In this study,performance and subsequent enzyme activity of beet armyworm reared on host plants from five families were investigated.Significant differences were found in development, fecundity and enzyme activity on different host plants. Survival ratewas the highest (42.8%) on asparagus lettuce (Lactuca sativar var. asparagina) and the lowest (17.0%) on sweet pepper(Capsicum annuum). Larval duration was the shortest on asparagus lettuce (12.0 d), and was 43.4% longer on sweetpeppers (21.2 d). The activity of acetylcholine esterase (AChE) and carboxylesterase (CarE) in 3rd instar larvae, andsoluble carbohydrate and crude protein contents in different host plants were determined. AChE activity was the highestin the larvae feeding on Chinese cabbage (Brassica rapa), but declined by nearly 60% on maize (Zea mays) seedlings. Theratio of soluble carbohydrate content to crude protein content in host plants was found to have a positive effect onoviposition and a negative correlation with larval duration and life time (from larval to adult stages) of the insect.