A new, unusually large, Clavicornaltica Scherer, 1974 flea beetle from Borneo, described and sequenced in the field by citizen scientists (Coleoptera, Chrysomelidae, Galerucinae).

Background: The genus Clavicornaltica Scherer 1974 consists of very small, soil-dwelling flea beetles in South, Southeast and East Asia. Due to their diminutive size and morphological similarities, very little is known about their ecology and taxonomical diversity. It is likely that further studies will reveal this genus to be much more speciose than the 30 species currently recognised. New information: A new species of Clavicornaltica from Brunei Darussalam is described, C.mataikanensis Otani et al., sp. nov. This is the second species of this genus recorded from Ulu Temburong National Park.

Costs of weaponry: Unarmed males sire more offspring than armed males in a male-dimorphic mite.

Morphological structures used as weapons in male-male competition are not only costly to develop but are also probably costly to maintain during adulthood. Therefore, having weapons could reduce the energy available for other fitness-enhancing actions, such as post-copulatory investment. We tested the hypothesis that armed males make lower post-copulatory investments than unarmed males, and that this difference will be most pronounced under food-limited conditions. We performed two experiments using the male-dimorphic bulb mite Rhizoglyphus robini, in which males are either armed "fighters" or unarmed "scramblers." Firstly, we tested whether fighters and scramblers differed in their reproductive output after being starved or fed for 1 or 2 weeks. Secondly, we measured the reproductive output of scramblers and fighters (starved or fed) after one, two or three consecutive matings. Scramblers sired more offspring than fighters after 1 week, but scramblers and fighters only sired a few offspring after 2 weeks. Scramblers also sired more offspring than fighters at the first mating, and males rarely sired offspring after consecutive matings. Contrary to our hypothesis, the fecundity of starved and fed males did not differ. The higher reproductive output of scramblers suggests that, regardless of nutritional state, scramblers make larger post-copulatory investments than fighters. Alternatively, (cryptic) female choice generally favours scramblers. Why the morphs differed in their reproductive output is unclear. Neither morph performed well relatively late in life or after multiple matings. It remains to be investigated to what extent the apparent scrambler advantage contributes to the maintenance and evolution of male morph expression.

Life-history consequences of bidirectional selection for male morph in a male-dimorphic bulb mite.

Intralocus sexual conflict (IASC) arises when males and females have different trait optima. Some males pursue different alternative reproductive tactics (ARTs) with different trait optima, resulting in different strengths of IASC. Consequently, for instance daughter fitness is differentially affected by her sire's morph. We tested if-and which-other life-history traits correlatively change in bidirectional, artificial selection experiments for ARTs. We used the male-dimorphic bulb mite Rhizoglyphus robini, the males of which are high-fitness 'fighters' or low-fitness 'scramblers'. Twice in each of the five generations of selection, we assessed clutch composition (number of mites of the various life stages present) and size (total number of offspring). Furthermore, we tracked offspring from egg to adulthood in the first and final generation to detect differences between selection lines in the size and duration of stages, and in maturation time. We found that selection for male morph increased the frequency of that morph. Furthermore, compared to fighter lines, scrambler lines produced more females, which laid larger eggs (in the final generations), and maintained a higher egg-laying rate for longer. Otherwise, our results showed no consistent differences between the selection lines in clutch size and composition, life stage size or duration, or maturation time. Though we found few correlated life-history trait changes in response to selection on male morph, the differences in egg laying rate and egg size suggest that IASC between fighters is costlier to females than IASC with scramblers. We hypothesize that these differences in reproductive traits allow fighter-offspring to perform better in small, declining populations but scrambler-offspring to perform better in large, growing populations.

Male behavioural plasticity depends on maternal mating status in the two-spotted spider mite.

In haplodiploid organisms including the two-spotted spider mite, Tetranychus urticae (Acari: Tetranychidae), both unmated and mated females can produce male offspring. A previous study reported that males produced by unmated females (UM males) find pre-reproductive females more quickly than males produced by mated females (M males) in T. urticae. However, it remains unclear what factors cause the difference. We investigated effects of maternal mating status on mate-searching behaviour of their sons by changing the sons' developmental environment. In T. urticae, the primary sex ratio of mated-female colonies is female-biased. For both UM and M males, half of individuals were reared with males to imitate unmated-female colonies, whereas the rest were reared with females to imitate mated-female colonies. In UM males, individuals that had developed with males found pre-reproductive females more quickly than those that had developed with females. However, such a difference was not observed in M males. This indicates that behavioural response to the developmental environment differs between UM and M males. It means that the behavioural plasticity depends on maternal mating status. When males were individually reared, however, there was no significant difference in the mate-searching behaviour between UM and M males, indicating that maternal mating status does not independently affect their sons' mate-searching behaviour. This study showed that male mate-searching behaviour is changed by their developmental environment and maternal mating status. This behavioural plasticity depending on maternal mating status is the first reported in haplodiploid organisms.