Occurrence,properties and biological implications of the active uptake of water vapour from the atmosphere in Psocoptera

Water vapour absorption is shown to occur in 22 species of Psocoptera inhabiting diverse environments and representing all major groups of this insect order. Evidently the faculty is a common feature of the whole order and it seems not to be related to specific environmental conditions. For the first time water vapour uptake could be demonstrated in fully winged and flying insects. The critical equilibrium humidities vary considerably among different species ranging from 58 to 85% r.h. Marked interspecific differences are also observed in water loss and uptake rates but no clear correlation with habitat or systematic group is recognizable. The uptake rates of Psocoptera are among the highest of all arthropods investigated so far. From weight recordings with a sensitive microbalance it could be seen that continuous operation of the uptake mechanism is restricted to limited periods of time of less than 1 hr regardless of the water status of the animals. Initiation and termination of the uptake process are abrupt and continuous uptake proceeds at a constant rate at a given relative humidity. Uptake rates are humidity-dependent decreasing with falling relative humidity whereas the adjustment of the equilibrium level of body water is independent of ambient humidity. Equilibrium is maintained by intermittent operation of the uptake mechanism within ca. 3% of body water mass. The uptake mechanism exhibits marked sensitivity to starvation in most members of the Psocomorpha. Some features of the uptake process of Psocoptera are in close agreement with those of Mallophaga reflecting the close relationship between the two groups.     

A Proposed Role for the Cuticular Fatty Amides of Liposcelis bostrychophila (Psocoptera: Liposcelidae) in Preventing Adhesion of Entomopathogenic Fungi with Dry-conidia

Maximum challenge exposure of Liposcelis bostrychophila to Beauveria bassiana, Paecilomyces fumosoroseus, Aspergillus parasiticus or Metarhizium anisopliae resulted in no more than 16% mortality. We investigated several of L. bostrychophila's cuticular lipids for possible contributions to its tolerance for entomopathogenic fungi. Saturated C14 and C16 fatty acids did not reduce the germination rates of B. bassiana or M. anisopliae conidia. Saturated C6 to C12 fatty acids that have not been identified in L. bostrychophila cuticular extracts significantly reduced germination, but the reduction was mitigated by the presence of stearamide. Cis-6-hexadecenal did not affect germination rates. Mycelial growth of either fungal species did not occur in the presence of caprylic acid, was reduced by the presence of lauric acid, and was not significantly affected by palmitic acid. Liposcelis bostrychophila is the only insect for which fatty acid amides have been identified as cuticular components. Stearamide, its major fatty amide, did not reduce germination of B. bassiana or M. anisopliae conidia or growth of their mycelia. Adhesion of conidia to stearamide preparations did not differ significantly from adhesion to the cuticle of L. bostrychophila. Pretreatment of a beetle known to be fungus-susceptible, larval Oryzaephilus surinamensis, with stearamide significantly decreased adhesion of B. bassiana or M. anisopliae conidia to their cuticles. This evidence indicates that cuticular fatty amides may contribute to L. bostrychophila's tolerance for entomopathogenic fungi by decreasing hydrophobicity and static charge, thereby reducing conidial adhesion.     

Rates of gene rearrangement and nucleotide substitution are correlated in the mitochondrial genomes of insects

A number of studies indicated that lineages of animals with high rates of mitochondrial (mt) gene rearrangement might have high rates of mt nucleotide substitution. We chose the hemipteroid assemblage and the Insecta to test the idea that rates of mt gene rearrangement and mt nucleotide substitution are correlated. For this purpose, we sequenced the mt genome of a lepidopsocid from the Psocoptera, the only order of hemipteroid insects for which an entire mtDNA sequence is not available. The mt genome of this lepidopsocid is circular, 16,924 bp long, and contains 37 genes and a putative control region; seven tRNA genes and a protein-coding gene in this genome have changed positions relative to the ancestral arrangement of mt genes of insects. We then compared the relative rates of nucleotide substitution among species from each of the four orders of hemipteroid insects and among the 20 insects whose mt genomes have been sequenced entirely. All comparisons among the hemipteroid insects showed that species with higher rates of gene rearrangement also had significantly higher rates of nucleotide substitution statistically than did species with lower rates of gene rearrangement. In comparisons among the 20 insects, where the mt genomes of the two species differed by more than five breakpoints, the more rearranged species always had a significantly higher rate of nucleotide substitution than the less rearranged species. However, in comparisons where the mt genomes of two species differed by five or less breakpoints, the more rearranged species did not always have a significantly higher rate of nucleotide substitution than the less rearranged species. We tested the statistical significance of the correlation between the rates of mt gene rearrangement and mt nucleotide substitution with nine pairs of insects that were phylogenetically independent from one another. We found that the correlation was positive and statistically significant (R2 = 0.73, P = 0.01; Rs = 0.67, P < 0.05). We propose that increased rates of nucleotide substitution may lead to increased rates of gene rearrangement in the mt genomes of insects.     

Elevated genetic diversity of mitochondrial genes in asexual populations of Bark Lice ('Psocoptera': Echmepteryx hageni)

Asexual reproduction is commonly thought to be associated with low genetic diversity in animals. Echmepteryx hageni (Insecta: 'Psocoptera') is one of several psocopteran species that are primarily parthenogenetic, but also exists in small, isolated sexual populations. We used mitochondrial DNA sequences to investigate the population history and genealogical relationships between the sexual and asexual forms of this species. The asexual population of E. hageni exhibits extremely high mitochondrial haplotype diversity (H=0.98), whereas the sexual forms had significantly lower haplotypic diversity (H=0.25, after correcting for sample size). This diversity in asexuals represents one the greatest genetic diversities reported for asexual animals in the literature. Nucleotide diversities were also higher in asexual compared to sexual populations (π=0.0071 vs. 0.00027). Compared to other reported estimates of π in insects, asexual nucleotide diversity is high, but not remarkably elevated. Three hypotheses might explain the elevated genetic diversity of asexual populations: (i) larger effective population size, (ii) greater mutation rate or (iii) possible recent origin of sexuals. In addition, phylogeographic analysis revealed little geographic structure among asexual E. hageni, although specimens from the upper Midwest form a single clade and are genetically differentiated. The mismatch distribution and neutrality tests indicate a historical population size increase, possibly associated with expansion from glacial refugia.     

Structure and evolution of the stigmapophysis—A unique repose wing-coupling structure in Psocodea

The gain of foldable wings is regarded as one of the key innovations enabling the present-day diversity of neopteran insects. Wing folding allows compact housing of the wings and shields the insect body from damage. Wing-fixing systems have evolved in some insects, probably to increase the durability of the shielding function by the wings. Bark lice (Psocodea) are known to possess a unique wing-to-wing repose coupling system, but a detailed morphological and evolutionary study of this system is lacking. In this study, we examined this repose coupling structure by SEM in 32 species including representatives of all three suborders of bark lice (Trogiomorpha, Troctomorpha and Psocomorpha). We concluded that the repose wing-coupling apparatus independently evolved twice within Psocodea. In Trogiomorpha, the apparatus is located on the subcostal vein of the forewing and is composed of elongated rib-like structures. In Troctomorpha and Psocomorpha, in contrast, the repose coupling structure is located on the radius vein of the forewing and is formed by a swollen vein. These morphological and developmental differences in the repose coupling structures also provide phylogenetic information at different systematic levels.     

Reinterpretations of clypeus and maxilla in Psocoptera, and their significance in phylogeny of Paraneoptera (Insecta: Neoptera)

Morphology of the head and mouthparts in Psocoptera was investigated, and revised interpretations for clypeus and maxilla were proposed. The convex plate in the frontal region of the head capsule is the postclypeus, rather than the frons; the galea is clearly differentiated from the stipes and the origin of the stipito-lacinial muscle is partly shifted from the stipes to the base of the galea; the cardo is completely fused with the stipes without any suture or sulcus. Brief discussions on the evolution of piercing and sucking mouthparts and on the phylogeny of Paraneoptera were provided, based on these revised interpretations.     

沼科和上科一新属二新种记述(目:亚目)

沼科Elipsocidae我国香港曾记载一种,Elipsocus oligotricuhus Thornton,1959,上科Epipsocidae台湾记载一种,Epipsocus hageni Banks,1937,共2种。华立中(1987)记载有3种,其中把香港的Elipsocus oligotricuhus分放于两个科的两个属中,同时Epipsocus hageni为N.Banks 1937记述,并非1917。本文记述了采自宁夏、陕西的沼科1新属2新种(均为短翅雌虫);云南的上科1新种,至此我国两科共5种。     

云南省虱科三新种（目：粉亚目）

本文记述了云南省虱科虱属３新种,Ｌｉｐｅｓｃｅｌｉｓｅｌｅｇａｎｔｉｓｓｐ．ｎ．,Ｌｉｐｏｓｃｅｌｉｓｎｉｇｒｉｔｉｂｉａｓｐ．ｎ．和Ｌｉｐｏｓｃｅｌｉｓｙｕｎｎａｎｉｅｎｓｉｓｓｐ．ｎ．。