Homeotic gene expression in the locust Schistocerca: An antibody that detects conserved epitopes in ultrabithorax and abdominal-A proteins

To investigate what role homeotic genes may play in morphological evolution, we are comparing homeotic gene expression in two very different insects, Drosophila (Diptera) and Schistocerca (Orthoptera). In this paper we describe a monoclonal antibody, FP6.87, that recognizes the products of both the Ultrabithorax (Ubx) and abdominal-A (abd-A) genes in Drosophila, via an epitope common to the carboxy terminal region of these two proteins. This antibody recognizes nuclear antigens present in the posterior thorax and abdomen of Schistocerca. We infer that it recognizes the Schistocerca homolog of UBX protein, and probably also of ABD-A. As the distribution of Schistocerca ABD-A protein is already known, we can use this reagent to map the expression of Schistocerca UBX in the thorax and anterior abdomen, where ABD-A is not expressed. Both the general domain, and many of the details, of UBX exp ression are remarkably conserved compared with Drosophila. Thus UBX expression extends back from T2 in the ectoderm (including the CNS), but only from A1 in the mesoderm. As noted for other bithorax complex genes in Schistocerca, expression begins in the abdomen, at or shortly before the time of segmentation. It only later spreads anteriorly to the thorax. For much of embryogene-sis, the expression of UBX in the thoracic epidermis is largely restricted to the T3 limb. Inthis limb, UBX is strikingly regulated, in a complex pattern that reflects limb segmentation. Reviewing these and earlier observations, we conclude that evolutionary changes affect both the precise regulation of homeotic genes within segments, and probably also the spectrum of downstream genes that respond to homeotic gene expression in a given tissue. Overall domains of homeotic gene expression appear to be well conserved between different insect groups, though a change in the extent and timing of homeotic gene expression may underlie the modification of the posterior abdomen in different insect groups. © 1994 Wiley-Liss, Inc.     

Monograph of the Afrotropical species of Scelio Latreille (Hymenoptera,Platygastridae), egg parasitoids of acridid grasshoppers (Orthoptera,Acrididae)

The genus Scelio is a cosmopolitan and speciose group of solitary parasitoids of the eggs of short-horned grasshoppers (Orthoptera: Acrididae). A number of these hosts are important pests, including plague locusts of the genus Schistocerca. Species of Scelio are recognized as potentially important biological control agents, but this possibility has yet to be fully realized, in part because the species-level taxonomy is still incompletely developed. The species of the pulchripennis group have been recently revised. As a continuation of this effort, here we revise the Afrotropical species of Scelio, excluding the pulchripennis species group. Sixty two (62) species are treated, 48 of which are new. Species are classified into the following species groups: ernstii (12 species, 9 new), howardi (23 species, 19 new), ipomeae (6 species, 5 new), irwini (4 species, 3 new), simoni (3 new species) and walkeri (12 species, 9 new). Keys to species groups and to the species within each group are provided. New species described are: S. albatus Yoder, sp. n., S. aphares Yoder, sp. n., S. apospastos Yoder, sp. n., S. ardelio Yoder, sp. n., S. aurantium Yoder, sp. n., S. balo Valerio & Yoder, sp. n., S. bayanga Yoder, sp. n., S. bubulo Yoder, sp. n., S. cano Yoder, sp. n., S. clypeatus Yoder, sp. n., S. concavus Yoder, sp. n., S. copelandi Yoder, sp. n., S. crepo Yoder, sp. n., S. destico Yoder, sp. n., S. dupondi Yoder, sp. n., S. effervesco Yoder, sp. n., S. erugatus Yoder, sp. n., S. exophthalmus Yoder, sp. n., S. fremo Valerio & Yoder, sp. n., S. gemo Yoder, sp. n., S. grunnio Yoder, sp. n., S. harinhalai Yoder, sp. n., S. igland Yoder, sp. n., S. impostor Yoder, sp. n., S. irwini Yoder, sp. n., S. janseni Yoder, sp. n., S. latro Yoder, sp. n., S. memorabilis Yoder, sp. n., S. modulus Yoder, sp. n., S. mutio Yoder, sp. n., S. ntchisii Yoder, sp. n., S. parkeri Yoder, sp. n., S. phaeoprora Yoder, sp. n., S. pilosilatus Yoder, sp. n., S. pipilo Yoder, sp. n., S. quasiclypeatus Yoder, sp. n., S. retifrons Yoder, sp. n., S. ructo Yoder, sp. n., S. scomma Yoder, sp. n., S. simoni Yoder, sp. n., S. simonolus Yoder, sp. n., S. somaliensis Yoder, sp. n., S. susurro Yoder, sp. n., S. tono Yoder, sp. n., S. transtrum Yoder, sp. n., S. tritus Yoder, sp. n., S. ululo Yoder, sp. n., S. vannoorti Valerio & Yoder, sp. n. The following species are redescribed: S. afer Kieffer, S. chapmani Nixon, S. howardi Crawford, S. ipomeae Risbec, stat. n., S. mauritanicus Risbec, S. philippinensis Ashmead, S. remaudierei Ferrière, S. striatus Priesner,S. taylori Nixon, and S. zolotarevskyi Ferrière. The genus Lepidoscelio Kieffer is treated as a junior synonym of Scelio Latreille, syn. n.; its type species, Lepidoscelio fuscipennis Kieffer, 1905 is transferred to Scelio, renamed Scelio obscuripennis Johnson, nom. n. (preoccupied by Scelio fuscipennis Ashmead, 1887), and redescribed. The following additional species are transferred from Lepidoscelio to Scelio: S. cayennensis (Risbec), comb. n., S. insularis Ashmead, rev. comb., S. luteus (Cameron), comb. n., S. thoracicus Ashmead, rev. comb. Lectotypes are designated for S. africanus Risbec, S. ipomeae Risbec, S. mauritanicus Risbec, S. remaudierei Ferrière, S. sudanensis Ferrière, and S. zolotarevskyi Ferrière. Scelio gaudens Nixon is a junior synonym of Scelio striatus Priesner, syn. n.; Scelio africanus Risbec and Scelio clarus Fouts are both junior synonyms of Scelio afer Kieffer, syn. n.; Scelio sudanensis Ferrière and Scelio cheops Nixon are both junior synonyms of Scelio zolotarevskyi Ferrière, syn. n.; Scelio cahirensis Priesner is a junior synonym of Scelio mauritanicus Risbec, syn. n. The name Scelio chapmanni Nixon is an incorrect original spelling, requiring an emendation to S. chapmani. Digital versions of the identification keys are available at http://www.waspweb.org/Platygastroidea/Keys/index.htm     

RECENT BIO ACOUSTIC PUBLICATIONS (mainly 1993)

ABSTRACT

Although much research has been done to describe the degradation of sound signals propagating in natural habitats, the directional cues of sound have so far been neglected. This paper describes a first approach to quantifying the degradation of directional cues in sound propagating parallel to the ground in a grassland habitat of orthopteran insects. A matched pair of probe microphones measured the sound amplitude and phase close to the ears of grasshopper carcasses for 12 evenly spaced directions of sound incidence. The degradation was found to increase with frequency and distance from the sound source and to decrease with distance from the ground. The acoustical data were used to predict how well animals with different auditory systems can determine the direction of the sender. At one position in the habitat, the predictions were compared with the pattern of phonotactic responses of live grasshoppers. Amplitude cues appear to degrade much faster with distance than phase cues. Animals exploiting phase cues may therefore maintain a reasonable directional hearing when the amplitude cues no longer make sense. The pressure-difference-receiver type of ears responds to phase differences, and these ears may be particularly suited to overcoming the degradation of directional cues. This suggests that the possession of such ears may be an adaptation not only to small body size (relative to wavelength), but also to the acoustic properties of the habitat.     

Competition among the adults of three grasshoppers (Orthop., Acrididae) on an alpine grassland

Abstract:  The intraspecific and interspecific competition among the adults of three common grasshoppers, Angaracris rhodopa (Fischer-Waldheim), Chorthippus dubius (Zubovsky) and Chorthippus fallax (Zubovsky) was investigated on Ganjia High Mountain Grassland in north-west China. The results indicated a strong intraspecific competition within species at high densities. The interspecific competition between the larger-sized species, A. rhodopa , and the smaller-sized species, C. dubius or C. fallax , was weak, while competition between C. dubius and C. fallax was strong. An asymmetric competitive interaction in mortality and fecundity associated with the diet and size was observed among the three species. Competition was strong between the two species that had a similar diet. The large-sized species had higher mortality rates and lower fecundity than the smaller-sized species. Intraspecific competition between the three species was mainly affected by food limitation, while interspecific competition was mainly associated with food limitation as well as the grasshoppers' adaptation to the environment.     

Developmental response to a seasonal time constraint: the effects of photoperiod on reproduction in the grasshopper Romalea microptera

Abstract.  1. Some organisms respond adaptively to seasonal time constraints by altering development time to life-history transitions (e.g. metamorphosis, oviposition). Such life-history changes may have costs (e.g. reduced fecundity, mass, offspring quality).
2. The hypothesis that a northern population of the grasshopper Romalea microptera (Beauvois) would show adaptive plasticity in oviposition timing in response to seasonal time constraints was tested by manipulating photoperiod to simulate the middle of the active season (Long photoperiod), the end of the active season (Short photoperiod), and seasonal change (photoperiod Declining from long to short). Females received either high or low food rations. Short or Declining photoperiod were predicted to induce early oviposition with costs of reduced egg number, post-oviposition mass, or egg size, particularly in low-food females.
3. Effects of food ration and photoperiod, but not interaction, were significant in failure time analysis of age at oviposition. mancova on age at oviposition, egg number, and post-oviposition mass yielded similar effects. The multivariate effect of photoperiod resulted primarily from reduced time to oviposition in Short or Declining photoperiod. No costs in egg number or post-oviposition mass were associated with this photoperiod-induced reduction in time to oviposition. The multivariate effect of food ration resulted mainly from lower egg number with low food. Food ration affected egg size, but photoperiod and interaction did not. In all cases, Short and Declining photoperiod produced similar effects.
4. In its northern range, R. microptera accelerates reproduction in response to seasonal constraints, a response that may be adaptive. How R. microptera avoids costs associated with this reduced pre-oviposition period remains unknown.     

Nocturnal city lighting elicits a macroscale response from an insect outbreak population

Anthropogenic environmental change affects organisms by exposing them to enhanced sensory stimuli that can elicit novel behavioural responses. A pervasive feature of the built environment is artificial nocturnal lighting, and brightly lit urban areas can influence organism abundance, distribution and community structure within proximate landscapes. In some cases, the attractive or disorienting effect of artificial light at night can draw animals into highly unfavourable habitats, acting as a macroscale attractive ecological sink. Despite their significance for animal ecology, identifying cases of these phenomena and determining their effective scales and the number of organisms impacted remains challenging. Using an integrated set of remote-sensing observations, we quantify the effect of a large-scale attractive sink on nocturnal flights of an outbreak insect population in Las Vegas, USA. At the peak of the outbreak, over 45 million grasshoppers took flight across the region, with the greatest numbers concentrating over high-intensity city lighting. Patterns of dusk ascent from vegetated habitat toward urban areas suggest a daily pull toward a time-varying nocturnal attractive sink. The strength of this attractor varies with grasshopper density. These observations provide the first macroscale characterization of the effects of nocturnal urban lighting on the behaviour of regional insect populations and demonstrate the link between insect perception of the built environment and resulting changes in spatial and movement ecology. As human-induced environmental change continues to affect insect populations, understanding the impacts of nocturnal light on insect behaviour and fitness will be vital to developing robust large-scale management and conservation strategies.     

Tropical grasshopper glutathione-S-transferase and detoxification of plant allelochemicals in Calotropis procera

Poecilocerus bufonius inhabits Saudi Arabia and uses Calotropis procera as its main host plant. Cardenolids of this plant are used by this grasshopper as chemical defence against the natural enemies. The activity of enzyme detoxification in mid-gut wall for these allelochemicals has been determined in this study. Results indicate that the activity of glutathione-S-transferase (GST) was significantly higher after 24 hours of feeding on the main host plant but no difference has been found after one, two, four and five hours of feeding.     

Seasonal pattern in population dynamics and host plant use of non‐swarming Ruspolia differens Serville (Orthoptera: Tettigoniidae)

The edible Ruspolia differens (Serville) (Orthoptera: Tettigoniidae) is an important source of food in East Africa, but the seasonality of its population dynamics and host plant use are not fully understood. We studied seasonal patterns in the population density and relative frequency of developmental stages, sexes, colour morphs and host plants of the non‐swarming R. differens at two study sites in central Uganda over 15 months. Linear mixed models were used to study how precipitation and Enhanced Vegetation Index (EVI) predict population density and relative frequency of developmental stages, sexes, colour morphs and host plants. The results showed that all developmental stages of non‐swarming R. differens were found in the field throughout the year. The population densities of R. differens were high in wet seasons and low in dry seasons and were best predicted by the EVI of the previous month. The sex ratio of the non‐swarming R. differens populations was female biased. The proportion of males and green colour morphs increased during and after the rainy season. The use of host plants fluctuated seasonally so that during the greener seasons individuals used the more preferred host Panicum maximum more frequently. Overall, our work indicates that R. differens has a seasonal dynamic so that vegetation greenness can be used to forecast non‐swarming R. differens population densities. Our results also suggest that source populations for swarming individuals might have a local origin. This is important for the management of habitats for reproduction and conservation of viable populations of R. differens in East Africa.     

DIVERGENCE IN MORPHOLOGY AND MATING SIGNALS,AND ASSORTATIVE MATING AMONG POPULATIONS OF CHORTHIPPUS PARALLELUS (ORTHOPTERA: ACRIDIDAE)

Three geographically widely separated populations of the grasshopper Chorthippus parallelus (Orthoptera: Acrididae) have been examined for morphological divergence, divergence in characteristics of the acoustic sexual signals of males, and assortative mating. Significant assortative mating existed between two of the three pairwise combinations of populations in multiple-choice tests. This may be caused by divergence in three of the four acoustic signal parameters measured. The populations also differed in morphology, including characters associated with signal production. The results are discussed in relation to theories for the origin of premating isolation, and it is argued that the observed divergence has developed rapidly, possibly indicating the action of selection. However, this selection could not have been caused by interactions with closely related taxa.     

陕西延安北洛河流域蝗虫群落多样性研究

为了寻求有害蝗虫的防治对策,深入研究蝗虫生物多样性,用多样性指数、相似性分析等方法比较分析了延安北洛河流域不同生境中蝗虫群落组成。结果表明:草地中占有的属种数量均最高,灌草丛和农田中蝗虫的科属种都相对较低。不同生境蝗虫多样性指数的排列顺序为草地>河滩>灌草丛>农田,草地的多样性指数最高,农田的多样性指数最低。丰富度指数的变化趋势与多样性指数一致,而优势度指数却恰好与二者的顺序相反。在相似性分析中,草地和河滩相似性系数最大,说明草地和河滩这两种生境蝗虫种类组成的相似性较大,具有更多的共同种,从而可以推知草地和河滩的生境条件有一定的相似性,而农田和草地是两种完全不同的生境。