Influence of weather conditions and density of Doru luteipes (Dermaptera: Forficulidae) on Diatraea saccharalis (Lepidoptera: Crambidae) egg mortality

The influence of weather factors and the predator Doru luteipes Scudder density on Diatraea saccharalis (F.) egg predation was studied. Mortality of D. saccharalis eggs was determined by artificially infesting maize plots with egg masses at various times within each of two maize-growing seasons. Each egg cohort was monitored every 24-48 h to determine the fate of eggs, and predation rates were calculated. Doru luteipes were sampled every 7-10 d, and the mean air temperature, the minimum percentage of relative humidity, and rainfall accumulations were recorded during the egg exposure period. To test the effects of abiotic and biotic variables on egg predation, we used a generalized linear model (GLM). Diatraea saccharalis egg predation was negatively associated with rainfall, whereas D. luteipes density and mean temperature were positively correlated with mortality. The implications of these findings for the management of D. saccharalis are discussed.     

Complete Mitochondrial Genome of the Free-Living Earwig, Challia fletcheri (Dermaptera: Pygidicranidae) and Phylogeny of Polyneoptera

The insect order Dermaptera, belonging to Polyneoptera, includes ～2,000 extant species, but no dermapteran mitochondrial genome has been sequenced. We sequenced the complete mitochondrial genome of the free-living earwig, Challia fletcheri, compared its genomic features to other available mitochondrial sequences from polyneopterous insects. In addition, the Dermaptera, together with the other known polyneopteran mitochondrial genome sequences (protein coding, ribosomal RNA, and transfer RNA genes), were employed to understand the phylogeny of Polyneoptera, one of the least resolved insect phylogenies, with emphasis on the placement of Dermaptera. The complete mitochondrial genome of C. fletcheri presents the following several unusual features: the longest size in insects is 20,456 bp; it harbors the largest tandem repeat units (TRU) among insects; it displays T- and G-skewness on the major strand and A- and C-skewness on the minor strand, which is a reversal of the general pattern found in most insect mitochondrial genomes, and it possesses a unique gene arrangement characterized by a series of gene translocations and/or inversions. The reversal pattern of skewness is explained in terms of inversion of replication origin. All phylogenetic analyses consistently placed Dermaptera as the sister to Plecoptera, leaving them as the most basal lineage of Polyneoptera or sister to Ephemeroptera, and placed Odonata consistently as the most basal lineage of the Pterygota.     

Biology and life tables for the predaceous earwig,Doru taeniatum [Derm.: Forficulidae]

The biology of the earwig,Doru taeniatum (Dohrn), a reported predator ofSpodoptera frugiperda (J. E. Smith), was studied in the laboratory.D. taeniatum under laboratory conditions was easily reared, mated readily and females tended eggs and first instar nymphs.D. taeniatum developed through 4 nymphal instars and reached imago in approximately 30 days. It is an omnivore in the laboratory and capable of developing and reproduction on plant pollen alone, and on Lepidoptera eggs (Sitotroga carealella) (Olivier) alone. Immatures developed most rapidly and females were most fecund when fed either a combination ofS. cereallea eggs and pollen, orS. cerealella eggs alone. Approved as TA 20744 by Director, Texas Agricultural Experiment Station.     

The Effect of Female Condition on Maternal Care in the European Earwig

Parental care typically enhances offspring fitness at costs for tending parents. Asymmetries in genetic relatedness entail potential conflicts between parents and offspring over the duration and the amount of care. To understand how these conflicts are resolved evolutionarily, it is important to understand how individual condition affects offspring and parental behaviour and whether parents or offspring make active choices in their interactions. Condition effects on offspring have been broadly studied, but the effect of parental condition on parent–offspring interactions is less well understood, in particular in species where care is facultative and offspring have the option to beg for food from the parents or to self‐forage. In this study, we carried out two experiments in the European earwig Forficula auricularia, a system where females provide facultative care, in which we manipulated female condition (through a high‐food and low‐food treatment) and the degree by which mothers and offspring could make active choices. In a first experiment, where female mobility was limited, female condition had no significant effect on the rate of offspring self‐foraging, which increased with nymph age. In a second experiment, nymph access to food was limited and females in poor nutritional condition provided food to significantly fewer nymphs than high condition females. In both experiments, offspring attendance remained at a constantly high level and was independent of female condition even after experimental separation of females and offspring. Our results show that earwig nymphs do not use cues of female condition to adjust rates of self‐foraging, that females control food provisioning depending on their own condition, and that females and nymphs share control over offspring attendance, a form of care not influenced by female condition.     

Matriphagy in the hump earwig, Anechura harmandi (Dermaptera: Forficulidae), increases the survival rates of the offspring

Females of the hump earwig, Anechura harmandi, are completely consumed by their offspring at the end of their care (matriphagy). The effect of this matriphagy was assessed by manipulative experiments. Matriphagy led to a delay in the dispersal of the nymphs and an increase in their survival rate. The same results were obtained when mothers were removed and the nymphs were given sufficient food. Females separated from their offspring after larval hatching failed to produce a second clutch, and three-quarters of them did not develop their ovaries. These results suggest that the survival of nymphs and their stay in the nest are dependent on food availability and that A. harmandi females are strictly semelparous.     

Parasitism of the common earwigForficula auricularia [Dermaptera: Forficulidae] by tachinid flies in an apple orchard

Earwigs (Forficula auricularia L.) were collected from an untreated apple orchard every 2 weeks from June to October 1979. Percentage parasitism at the times of collection was calculated from the numbers of parasitoids that emerged. Two tachinidsRhacodineura pallipes Fallen andDigonochaeta spinipennis Meigen parasitised earwigs, starting between 21 June and 5 July and continuing through July. Parasitism byR. pallipes reached a peak of 16 % in late July; fewer earwigs were parasitised byD. spinipennis. Both tachinids had one generation per year;D. spinipennis overwintered as puparia, andR. pallipes as larvae in earwig hosts or as adults. In the orchard, puparia of both tachinid species were hyperparasitised byDibrachys cavus (Walker) (Pteromalidae) andPhygadeuon vexator (Thunberg) (Ichneumonidae).     

Courtship Roles of Male and Female European Earwigs, Forficula auricularia L. (Dermaptera: Forficulidae), and Sexual Use of Forceps

Detailed observations of the courtship and mating of the European earwig Forficula auricularia revealed a complex of sexual behaviors for both males and females. A sequential analysis of the transition frequencies between male preceding-following behaviors showed that courtship is intricate and nonstereotyped. The significance of the male forceps was demonstrated by their use in early courtship with displays and later use as a tactile stimulus for the female. A study of males from which the forceps had been removed showed no mating by altered males. Male forcep length was bimodally distributed and positively allometric, while female forcep length was normally distributed. Males with longer forceps did not have a mating advantage. Receptive females were behaviorally active during courtship. The possible evolutionary development of the sexual dimorphism of the earwig is discussed.     

Observations on the biology of Hemimems talpoides (Insecta: Dermaptera)

The little known ectoparasitic insects of the genus Hemimerus lived and bred on a captive giant rat Cricetomys , allowing prolonged observation of their habits. They never normally left the host for more than a few seconds and never fed elsewhere than on the host. Food was taken from the skin, ears, eyes and mouth but the rat never showed serious irritation. Breeding was slow and possibly closely controlled by temperature. The position in copulation was quite different from that of typical Dermaptera.     

Taxonomic notes on the genus Strongylopsalis Burr (Dermaptera: Labiidae)

The male and female of a new species of Strongylopsalis are described from Bolivia. Carcinophora boliviana Bormans is redescribed, and its position in the genus Strongylopsalis is confirmed; a new name is proposed for S.boliviana Brindle. A key is given to the ten species now contained in Strongylopsalis, and notes on the distribution of the genus and its possible relationship to Marava are included.     

A review of the genus Tagalina Dohrn (Dermaptera: Pygidicranidae)

Tagalina semperi Dohrn and T. papua (Bormans) are shown to be distinct species. T.burri Hincks is synonymised with T. erythronota Gunther, and a lectotype is designated for the latter species. The specimens misidentified by Hincks as T. erythronota are described as hincksi sp.n., and curta sp.n. is described from central New Guinea. A key to the nine species of the genus is given, together with a short systematic list and notes on the distributions and type localities.     

Evolution of locomotory attachment pads in the Dermaptera (Insecta)

This contribution is the first comparative SEM study of tarsal and pretarsal structures of 18 dermapteran species, including epizoic Hemimeridae, rare Apachyidae, as well as basal Pygidicranidae. Our data reject the apparent uniformity of this taxon and show that representatives of Dermaptera have independently evolved both types of attachment mechanisms: hairy and smooth. Dermaptera possess a wide spectrum of attachment devices: arolia, euplantulae, tarsal surfaces covered with specialised tenent setae and other types of cuticular outgrowths. The groundpattern of the pretarsal and tarsal attachment structures was reconstructed by mapping their characters onto a cladogram, generated without tarsal characters. In the groundpattern of recent Dermaptera, the tarsus consists of three tarsomeres. Presumably, the last common ancestor of the Dermaptera possessed an arolium, since this structure occurs in the most basal taxa: Diplatyidae, Karschiellidae (partim, adults), Pygidicranidae partim, and Apachyidae. The absence of arolium in two of the pygidicranid taxa is probably due to a secondary loss. The arolium seems to be reduced in the 'higher Dermaptera' and amongst them, only the Geracinae, which belong to the Spongiphoridae and, hence, to the well supported Eudermaptera [European Journal of Entomology, 98 (2001), 445], evolved this structure convergently. The character state distribution for euplantulae suggests their evolution being similar to that of the arolium. All species of Tagalina possess a specialised tarsus with a strongly dilated second tarsomere. The same applies to the Forficulidae. However, their relatively remote phylogenetic position to Tagalina burri is a convincing reason to assume convergent evolution of this character. The Chelisochidae, with a slender, elongated second tarsomere, possess a unique structure, which supports their monophyly. The special, heart shaped structure of the second tarsal segments in the Forficulidae suggests their monophyly. The attachment structures of Hemimerus vosseleri are highly derived and probably autapomorphic for this taxon.     

Postembryonic development of the cervicothoracic skeleton of Euborellia annulipes (Lucas) (Dermaptera: Labiduridae)

The nymphal and adult cervicothoracic skeleton of Euborellia annulipes (Lucas) is described and discussed.     

The chromosomes of Arixenia esau Jordan (Dermaptera)

The parasitic insect Arixenia esau, a highly aberrant member of the order Dermaptera, shows n = 30 and has an XY sex determining mechanism. This karyotype is compared with those of the earwigs (Forficulina) and of Hemimerus bouvieri, a member of another aberrant parasitic suborder of the Dermaptera.Supported by Public Health Service Grant GM-07212 from the Division of General Medical Sciences, U.S. National Institutes of Health and by a grant from the Australian Research Grants Committee.     

The chromosomes of Hemimerus bouvieri chopard (Dermaptera)

The parasitic insect Hemimerus bouvieri, of rather uncertain systematic position but probably an aberrant member of the order Dermaptera, shows 2n =7, 2n =8. The chromosomes appear to be holocentric. There is an X₁X₂Y sex chromosome mechanism in the male, and a sex-trivalent is formed at meiosis. The two autosomal bivalents seem to be chiasmate and the members of the sex-trivalent may also be held together by chiasmata, but this is uncertain. In general, these cytological features are similar to those of true earwigs (Forficulina).Supported by Public Health Service Grant GM-07212 from the Division of General Medical Seiendes, U.S. National Institutes of Health and by a grant from the Australian Research Grants Committee.     

Feeding habits ofForficula Senegalensis (Derm.: Forficulidae) on millet in the sudanese-sahelian zone of niger: Crop content analysis

Crop contents from 443 adults and 291 larvae ofForficula senegalensis Serv. living on millet in 1995 and 1996 were analyzed. During its pre-reproductive phase, throughout its larval development, and during its post-teneral phase, the insect eats animal prey and pollen, but no chlorophyllous tissues.F. senegalensis is therefore not phyllophagous, but rather a pollen consumer and a predator of the insect fauna living on millet. The status of this earwig as a pest of millet must be reconsidered.     

Earwig (Forficula auricularia) predation on the woolly apple aphid, Eriosoma lanigerum

Woolly apply aphid predation by the common earwig, Forficula auricularia L., and other predators was compared in high, intermediate and low earwig density plots of mature apple trees at an experimental orchard in the Netherlands. Aphid colonies were discovered and exterminated primarily by earwigs much more rapidly in the high and intermediate earwig density plots than in the low density plots. Where earwigs were excluded from trees by Tanglefoot bands around the trunks, woolly apple aphids infested 30–35% of new growth shoots whereas less than 10% of the shoots were infested where earwigs were relatively abundant.Several factors including the availability of alternate prey (e.g. Aphis pomi De Geer), earwig developmental phenology and weather probably influenced the outcome of the predation experiments. Nevertheless earwigs play an important role in suppressing woolly apple aphid populations and are potentially important, naturally occurring biological control agents for this pest.

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Résumé L'action prédatrice exercée sur le puceron lanigère par le perceoreille commun, Forficula auricularia, et par d'autres prédateurs, a été comparée dans des parcelles d'un verger expérimental de pommiers adultes aux Pays-Bas. Ces parcelles étaient caractérisées par des densités fortes, intermédiaires, et basses en perce-oreilles. Les colonies de pucerons ont été découvertes et exterminées principalement par les perce-oreilles beaucoup plus rapidement dans les parcelles à forte et moyenne densité de perce-oreilles que dans celles à faible densité. Les pucerons lanigères ont colonisé 30 à 35% des nouvelles pousses lorsque les perce-oreilles étaient exclus par une barrière mécanique (Tanglefoot), alors que moins de 10% des pousses ont été infestées lorsque les perce-oreilles étaient relativement abondants.Plusieurs facterus ont probablement influencé le résultat des expériences de prédation, notamment la présence de proies alternatives (par exemple Aphis pomi), la phénologie du développement des perce-oreilles et le climat. Néanmoins, les perce-oreilles ont joué un rôle important en limitant les populations du puceron lanigère, et constituent potentiellement d'importants agents de contrôle naturel de ce ravageur.

     

Mating Systems,Maternal and Biparental Care in Triggerfish (Balistidae)

Groups of the triggerfish Pseudobalistes fuscus and Odonus niger were studied from the underwater laboratory Neritica in Eilat, Gulf of Akaba, in the Red Sea. Mating and the roles of the sexes during broodcare seem to depend strongly on territory size, probably determined by shelter site and food availability, and territorial control- and defendability. The discussion considers why evolution has favoured maternal broodcare in the one case and biparental in the other.