Identification of 10 microsatellite loci in the earwig Labidura riparia (Dermaptera,Labiduridae)

Ten microsatellite loci were isolated from the earwig Labidura riparia (Pallas, 1773). The polymorphism of the loci was assessed in 24 individuals from one population. The number of alleles ranged from four to 11 alleles and observed and expected heterozygosities from 0.250 to 0.833 and from 0.551 to 0.861, respectively.     

Maternal behavior and clutch manipulation in the ring-legged earwig (Dermaptera: Carcinophoridae)

The expression and maintenance of maternal behavior in the earwig,Euborellia annulipes, was examined through manipulation of clutch size, age, and species and through observations of interactions between brooding females. Females underwent discrete gonadotrophic cycles culminating in oviposition of first clutches that were highly variable in size. Neither the head capsule width nor the age of the mother was correlated with clutch size. Maternal care extended through embryogenesis and for the week following hatching. Clutch removal significantly shortened the interclutch interval, indicating that the presence of brood inhibited the onset of the second gonadotrophic cycle. Brooding females readily accepted replacement clutches of the same age. Thus, mothers did not appear to distinguish their own eggs from those of other females. Experimental doubling of clutch size did not significantly reduce the proportion hatching or fledging. In contrast, reducing clutch size diminished the percentage successfully fledging. Manipulation of clutch age resulted in reduced hatching/fledging success. Placing two females, each with newly laid clutches, in the same cage usually resulted in egg transfer from the nest of one female to that of the other within 12 h. Nests of females with larger forceps were significantly more likely to contain both clutches. When mothers with first clutches were paired with mothers with third clutches, eggs were more likely to be transferred to the nest of the older female.E. annulipes females with newly laid clutches appeared to accept as replacement clutches eggs of the earwigDoru taeniatum. Alien clutches were maintained for the typical duration of embryogenesis; however, noD. taeniatum hatchlings were observed.     

内蒙古自治区上侏罗统最原始的蠼螋昆虫化石(昆虫纲:革翅目:始螋亚目)

我国上侏罗统牛津阶-基末利阶（163-150Ma)保存有完好的最原始的蠼螋昆虫化石,首次描述,分析和讨论了原始蠼螋后翅脉序特征,认为与现代生存的蠼螋后翅基本相同。因此,提出了与西方某些蠼螋昆虫分类学者不同的意见,认为始螋亚目（Aechidermaptera)应归入于革翅目（Dermaptera)之中,且视其为一个最原始的类群较为合理,内蒙古自治区这个原始类群的下列重要特征皆为首次发现;胸骨具有特殊的形态结构;革翅锁具（Tegmina locking device)和刺脊突（spiny crest)发育;前,中,后足跗节皆为5节;后足基节显著伸长;颈部被划分为前,后两个颈片;革翅后缘收缩变尖,上述5项被视为厚原始蠼螋特有的祖征,下列特征应为早期蠼螋共有的原始性状;虫体扁平,通常具毛;腹部侧缘彼此近平行;触角显长,丝状,多节（通常多于11节）;两只单眼发育;上颚具齿;中胸小盾片显大;革翅较长,通常具有明显的翅脉;股节具隆脊;爪和爪垫通常发育;腹部各节背板与腹板不重叠（两者位置非简单的上,下关系）;尾须柔软,多节,雌性产卵器鞘显著外伸,本文建立了始螋亚目1新科Sinopalaeo-dermatidae和2新属2新种Sinopalaeodermata neimonggolensis gen.et sp.nov,Jurassimedeola orientalis gen,et sp.nov。同时,对蠼螋昆虫的起源和演化重新进行了讨论,做出了与西方某些蠼螋昆虫研究者结论不同的推断。     

Possible influences of habitat characteristics on the evolution of semelparity and cannibalism in the hump earwigAnechura harmandi

The possible influences of life history and habitat characteristics on the evolution of semelparity and cannibalism in the hump earwigAnechura harmandi were studied. This species is univoltine and overwinters as an adult. Females laid single egg-batches during winter in nests under stones at a riverside in a valley. They took care of the eggs which hatched in early spring and the offspring ate their mother before dispersing. The valley was sometimes flooded in summer. Nymphs emerged as adults and dispersed to elsewhere before the rainy season arrived. They returned to the riverside after the rainy season. The flooding and/or summer heat seemed to be the selective force for the evolution of dispersal behavior and semelparity in this species. The cannibalism of the female parent by her offspring seemed to have readily evolved after the evolution of semelparity. The unfavorable environmental conditions seemed to have a large effect on the evolution of semelparity and cannibalism in this species.     

Juvenile hormone in earwigs: Roles in oogenesis,mating, and maternal behaviors

The role of juvenile hormone (JH) in courtship, mating, maternal behavior, and the ovarian cycle was studied in the ring-legged earwig, Euborellia annulipes (Lucas). The single, median corpus allatum makes and secretes JH III. JH III production was low in newly eclosed adult females, increasing as oocytes developed, maximal at about the time of oviposition, and low again in brooding females. Application of 35 or 122 μg JH III to newly eclosed females hastened the onset of courtship behavior, but had no effect on the age at which females first mated nor on the duration of mating, though the trend is toward advanced onset. Hormone treatment advanced the age of first oviposition and reduced clutch size and the proportion of eggs hatching but did not affect the interval from oviposition of the first clutch to oviposition of the second clutch, nor the size and proportion hatching of the second clutch. Acetone treatment and treatment with 6 μg JH III did not affect these parameters. Application of 50 μg JH III to females on the day of oviposition shortened the duration of maternal care and advanced the onset of the second gonadotropic cycle, compared with that of acetone-treated and precocene II-treated females. The duration of maternal care was positively correlated with the proportion of eggs hatching. JH titer analysis confirmed JH III to be the predominant hormone in this species and clearly demonstrated the absence of other homologues. This work also confirmed our hypothesis that intermediate to high levels of JH are associated with oocyte growth, mating, and cessation of maternal care; low levels of JH are associated with the period of maternal behavior and slow ovarian development. We are currently investigating factors which might regulate corpus allatum activity during the reproductive cycle and the subsequent period of maternal care. Arch. Insect Biochem. Physiol. 35:427–442, 1997. © 1997 Wiley-Liss, Inc.     

洞庭湖区苇田拟垫跗蠼螋研究

拟垫跗蠼螋Proreus simulans(Stal)的生物学,包括栖息习性,越冬虫态和越冬场所,卵的历期;各龄若虫的形态特征与历期;成虫的耐饥能力,交配、产卵习性,越冬期成虫呼吸率和呼吸商等内容。捕食作用研究结果表明,该天敌的食蚜日均捕食量随龄次增大,4龄达到最大,至成虫以后保持稳定;各龄若虫及咸虫的功能反应均属H011lngⅡ型;著者最后认为拟垫跗蠼螋是一种有利用价值的捕食性天敌,并提出保护利用措施。     

PATTERNS OF THRESHOLD EVOLUTION IN POLYPHENIC INSECTS UNDER DIFFERENT DEVELOPMENTAL MODELS

Two hypotheses address the evolution of polyphenic traits in insects. Under the developmental reprogramming model, individuals exceeding a threshold follow a different developmental pathway from individuals below the threshold. This decoupling is thought to free selection to independently hone alternative morphologies, increasing phenotypic plasticity and morphological diversity. Under the alternative model, extreme positive allometry explains the existence of alternative phenotypes and divergent phenotypes are developmentally coupled by a continuous reaction norm, such that selection on either morph acts on both. We test the hypothesis that continuous reaction norm polyphenisms, evolve through changes in the allometric parameters of even the smallest males with minimal trait expression, whereas threshold polyphenisms evolve independent of the allometric parameters of individuals below the threshold. We compare two polyphenic species; the dung beetle Onthophagus taurus, whose allometry has been modeled both as a threshold polyphenism and a continuous reaction norm and the earwig Forficula auricularia , whose allometry is best modeled with a discontinuous threshold. We find that across populations of both species, variation in forceps or horn allometry in minor males are correlated to the population's threshold. These findings suggest that regardless of developmental mode, alternative morphs do not evolve independently of one another.     

Frass sampling and baiting indicate European earwig (Forficula auricularia) foraging in orchards

Abstract:  Earwigs are significant generalist predators of a range of orchard pests, but quantitative assessment of earwig density and beneficial impact is difficult. A sampling system was designed and tested, based on field placement of polycarbonate tubes in apple trees as scotophase arboreal refugia. Tubes containing artificial diet and provided with a black plastic sleeve had the highest earwig counts. Tubes with diet or the black sleeve alone were less preferred. Presence of distinctive frass was also evident in polycarbonate tubes containing artificial diet, and earwig frass was recorded at a higher frequency than earwig presence, indicating foraging and detection of the tubes at a higher rate than their use as shelters. At the tree level, there was a weak correlation between frass abundance and predation rates on leafroller egg batches placed as baits in the canopy, but not with earwig density measured by corrugated cardboard rolls or diet tubes. Diet tubes have the potential to offer new insights into earwig foraging behaviour in orchards.     

Paternity and egg cannibalism in the ringlegged earwig Euborellia annulipes (Dermaptera: Anisolabididae)

Cannibalism is a common occurrence in nature, and many cannibals prey on relatively small and defenseless life stages, such as eggs or young juveniles. Such behavior provides many benefits to the cannibal, but cannibalistic individuals also face risks, including the cost of decreasing their inclusive fitness by eating close relatives such as siblings or offspring. This risk can be mitigated if cannibals can recognize and avoid preying on kin. Here, we tested whether male ringlegged earwigs Euborellia annulipes avoid cannibalizing eggs that they had sired. In this species, females care for their own eggs, but males provide no care and frequently prey upon eggs. We found that when presented with an unguarded clutch of eggs, male earwigs nearly always cannibalized some eggs, but that the proportion of eggs eaten was smaller if the male had sired the clutch. This suggests that males can distinguish between their own offspring and unrelated offspring and that they avoid harming their kin.