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Locusts
... Locusts are known to exhibit their densitydependent behavioral, physiological, and phenotypic polymorphism. 4,5 Under low population densities, locusts live in the "solitarious phase" characterized by camouflage coloration (Fig. 1), infrequent social interactions, and sedentary behavior. At high densities, locusts develop into the "gregarious phase" often with strikingly black-and-orange colored nymphs (Fig. 2), which march in cohesive "hopper bands" [4][5][6] (Fig. 3). ...
... 4,5 Under low population densities, locusts live in the "solitarious phase" characterized by camouflage coloration (Fig. 1), infrequent social interactions, and sedentary behavior. At high densities, locusts develop into the "gregarious phase" often with strikingly black-and-orange colored nymphs (Fig. 2), which march in cohesive "hopper bands" [4][5][6] (Fig. 3). The most spectacular differences between the phases are in behavior: the solitarious adults avoid each other except for mating, while the gregarious adults pack together in swarms (Fig. 4); they migrate, feed, mate, and lay eggs in crowds (Fig. 5). ...
... 6 Out of 6,400 described grasshopper species of the family Acrididae in the world, only about a dozen exhibit pronounced behavioral and/or morphological differences between phases, and should be considered locusts. 5 In other words, all locusts are grasshoppers, but only a few grasshoppers are locusts. The capacity to produce a swarming phase appeared independently a number of times in four subfamilies (Cyrtacanthacridinae, Calliptaminae, Gomphocerinae, and Oedipodinae) within the family Acrididae and is considered as a relatively recent trait in their evolution. ...
A dozen species of locusts (Orthoptera: Acrididae) are a major threat to
food security worldwide. Their outbreaks occur on every continent except
Antarctica, threatening the livelihood of 10% of the world's population.
The locusts are infamous for their voracity, polyphagy, and capacity for
long-distance migrations. Decades of research revealed very complex
bio-ecology of locusts. They exist in two, inter-convertible and
density-dependent states, or "phases." Despite the evident progress in
understanding locust behavior, our ability to predict and manage locust
outbreaks remains insufficient, as evidenced by locust plagues still
occurring during the 21st century. One of the main reasons is that
locusts typically inhabit remote and scarcely populated areas, and their
distribution ranges often spread across continents. This creates
tremendous obstacles for locust population monitoring and control.
Traditional ground locust surveys are inadequate to address the enormous
spatial scale of the locust problem in a limited window of time dictated
by the pest's development. Remote sensing (satellite information)
appears a promising tool in locust monitoring. Satellite data are
increasingly used for monitoring and forecasting two locust species, the
desert and the Australian plague locust. However, applications of this
geospatial technology to other locust species remain rare.
... Locusts are grasshopper species capable of expressing phase polyphenism, a form of phenotypic plasticity (Latchininsky, 2010). An increase in local population density, triggered by precipitation and vegetation development within favourable breeding areas (Latchininsky, 2010), favours inter-individual contacts and therefore gregarization (Latchininsky, 2013;Piou et al., 2013). ...
... Locusts are grasshopper species capable of expressing phase polyphenism, a form of phenotypic plasticity (Latchininsky, 2010). An increase in local population density, triggered by precipitation and vegetation development within favourable breeding areas (Latchininsky, 2010), favours inter-individual contacts and therefore gregarization (Latchininsky, 2013;Piou et al., 2013). The life cycle of the Asian Migratory locust, is closely synchronized with the development of the common reed as its primary host plant (Novityky, 1963). ...
The Asian Migratory locust (Locusta migratoria migratoria L.) is a pest that continuously threatens crops in the Amudarya River delta near the Aral Sea in Uzbekistan, Central Asia. Its development coincides with the growing period of its main food plant, a tall reed grass (Phragmites australis), which represents the predominant vegetation in the delta and which cover vast areas of the former Aral Sea, which is desiccating since the 1960s. Current locust survey methods and control practices would tremendously benefit from accurate and timely spatially explicit information on the potential locust habitat distribution. To that aim, satellite observation from the MODIS Terra/Aqua satellites and in-situ observations were combined to monitor potential locust habitats according to their corresponding risk of infestations along the growing season. A Random Forest (RF) algorithm was applied for classifying time series of MODIS enhanced vegetation index (EVI) from 2003 to 2014 at an 8-day interval. Based on an independent ground truth data set, classification accuracies of reeds posing a medium or high risk of locust infestation exceeded 89% on average. For the 12-year period covered in this study, an average of 7504 km² (28% of the observed area) was flagged as potential locust habitat and 5% represents a permanent high risk of locust infestation. Results are instrumental for predicting potential locust outbreaks and developing well-targeted management plans. The method offers positive perspectives for locust management and treatment of infested sites because it is able to deliver risk maps in near real time, with an accuracy of 80% in April-May which coincides with both locust hatching and the first control surveys. Such maps could help in rapid decision-making regarding control interventions against the initial locust congregations, and thus the efficiency of survey teams and the chemical treatments could be increased, thus potentially reducing environmental pollution while avoiding areas where treatments are most likely to cause environmental degradation.
... The desert locust Schistocerca gregaria migrates annually over several thousand kilometers through North Africa and the Middle East (Homberg 2015;Kennedy 1951). During these migrations, swarms of locusts devastate huge areas of agricultural crops (Enserink 2004;Latchininsky 2010). Therefore, the development of biological pest controls against locust swarms is an important political issue in those areas (Lomer et al. 2001). ...
Desert locusts (Schistocerca gregaria) sense the plane of dorsally presented polarized light through specialized dorsal eye regions that are likely adapted to exploit the polarization pattern of the blue sky for spatial orientation. Receptive fields of these dorsal rim photoreceptors and polarization-sensitive interneurons are directed toward the upper sky but may extend to elevations below 30°. Behavioral data, however, suggests that S. gregaria is even able to detect polarized light from ventral directions but physiological evidence for this is still lacking. In this study we characterized neurons in the locust brain showing polarization sensitivity at low elevations down to the horizon. In most neurons polarization sensitivity was absent or weak when stimulating from the zenith. All neurons, including projection and commissural neurons of the optic lobe and local interneurons of the central brain, are novel cell types, distinct from polarization-sensitive neurons studied so far. Painting dorsal rim areas in both eyes black to block visual input had no effect on the polarization sensitivity of these neurons, suggesting that they receive polarized light input from the main eye. A possible role of these neurons in flight stabilization or the perception of polarized light reflected from bodies of water or vegetation is discussed.
... In addition, food selection is highly influenced by both physical and chemical properties of plant leaves (Chapman 1990). Food preference in the CAL is also dependent on its developmental status, for example, CALs in solitarious phase feed only on limited number of plant species, while in the gregarious phase, they are less selective for food (Latchininsky 2010). ...
The Central American locust (CAL) Schistocerca piceifrons piceifrons Walker is one of the most harmful plant pests in the Yucatan Peninsula, where an important gregarious zone is located. The olfactory response and host plant acceptance by the CAL have not been studied in detail thus far. In this work, the olfactory response of the CAL to odor of various plant species was evaluated using an olfactometer test system. In addition, the host plant acceptance was assessed by the consumption of leaf area. Results showed that the CAL was highly attracted to odor of Pisonia aculeata. Evaluation of host plant acceptance showed that the CAL fed on Leucaena glauca and Waltheria americana, but not on P. aculeata or Guazuma ulmifolia. Analysis of leaf thickness, and leaf content of nitrogen (N) and carbon (C) showed that the CAL was attracted to plant species with low leaf C content.
... Locusts are grasshopper species capable of expressing phase polyphenism, a form of phenotypic plasticity that confers on them the capacity to change behavior, morphology, and life cycle from harmless solitarious phase individuals to gregarious phase individuals that form devastating bands and swarms through a process called gregarization (Latchininsky 2010; Pener & Simpson 2009; Simpson & Sword 2009;Simpson, Sword, & De Loof, 2005). The capacity to change phase was first identified by Uvarov (1921Uvarov ( , 1929 and is directly linked to local increases in population density in all locust species. ...
Locusts are grasshopper species that express phase polyphenism resulting in the expression of gregarious behaviors that favor the development of large devastating bands and swarms. Desert locust preventative management aims to prevent crop damage by controlling populations before they can reach high densities and form mass migrating swarms. The areas of potential gregarization for Desert locust are large and need to be physically assessed by survey teams for efficient preventative management. An ongoing research challenge is to be able to guide where prospection surveys should occur depending on local meteorological and vegetation conditions. In this study, we analyzed the relationship between historical prospection data of Desert locust observations from 2005 to 2009 and spatio-temporal statistics of a vegetation index gathered by remote-sensing with the help of multiple models of logistic regression. The vegetation index was a composite Normalized Difference Vegetation Index (NDVI) given every 16 days and at 250m spatial resolution (MOD13Q1 from MODIS satellite). The statistics extracted from this index were: 1) spatial means at different scales around the prospection point, 2) relative differences of NDVI variation through time before the prospection, and 3) large scale summary of vegetation quantity. The multi-model framework showed that vegetation development a month and a half before the survey was amongst the best predictors of locust presence. Also, the local vegetation quantity was not enough to predict locust presence. Vegetation quantity on a scale of few kilometers was a better predictor but varied non-linearly, reflecting specific biotope types that support Desert locust development. Using one of the best logistic regression model and NDVI data, we were able to derive a predictive model of probability of finding locusts in specific areas. This methodology should help in more efficiently focusing survey efforts on specific parts of the gregarization areas based on the predicted probability of locusts being present.
The term ‘locust’ is given to those species of grasshoppers, which are capable of forming large swarms under certain conditions. They belong to family Acrididae, suborder Caelifera, order Orthoptera and class Insecta. The locust swarms move over wide and distant areas and cause severe damage to cultivated and natural vegetation, where the swarms settle. There are many species of locusts, amongst which desert locust, Schistocerca gregaria, is the most damaging pest. The locust problem is not new. Since the beginning of civilisation, they have been a serious threat to agriculture. A substantial increase in locust population, which may cause serious devastation of crops, is known as outbreak. Each locust can exist in two main forms, i.e. solitary phase (phasis solitaria) and gregarious phase (phasis gregaria), which are quite distinct morphologically as well as behaviourally. An intermediate phase (phasis transiens) also occurs in between two extreme phases. Each locust is a grasshopper, but every grasshopper is not a locust.
En masse inoculations with Paranosema locustae, an intracellular parasite of adipose tissue of grasshoppers and locusts and the only microsporidium registered as a biocontrol agent, were conducted against crowded fourth-instar nymphs of the South American locust Schistocerca cancellata and the grasshoppers Dichroplus schulzi and Ronderosia bergii. Infection did not develop in the locust, but was highly prevalent in the two grasshopper species. We hypothesize that absolute absence of infection in S. cancellata may constitute a case of density-dependent prophylactic resistance, an elevation of the baseline immunity of an organism in order to cope with disease that is prevalent in species exhibiting phase polyphenism.
Economic importance of locusts is well established throughout the world owing to their swarming behaviour. The damage caused by the hoppers on a small scale is mostly confined to local vegetation, primarily crops. The crop damage goes unnoticed, but they are persistent in nature and the effects they leave on planned systems, such as crop fields, are much more serious. Therefore, many taxa (genera or species) of the family Acrididae are considered as potential pests of farms, forests and even pastures. The family comprises about 10,000 species in suborder Caelifera out of a total of nearly 11,000 species. These insects exist in two polymorphic forms, solitary and gregarious. Latter form results in migratory swarms of voraciously feeding hoppers that migrate in a much coordinated fashion. Damage caused is much more apparent and extensive leading to famine-like conditions. In general, distribution of locusts and grasshoppers decreases with increasing latitudes, i.e. their occurrence increases towards the equator. These insects are polyphagous rather than being host specific and consume a variety of unrelated plant species. They are well distributed throughout the world but show significant difference in different habitats. Difference in habitat relates directly to difference in host plants because of variability in various abiotic factors of ecosystem, like altitude, latitude, precipitation, etc. Because of these facts, they are reasonably good biotic indicators of threatened habitats or ecosystems and therefore help in conservation and preservation of particular areas. In this chapter, important locust species have been included. Their diagnostic characters, life cycle, economic importance and control measures have been provided. Though these insects are important pests but natural control by climate, parasitism and predators have not been found adequate. For that reason, various artificial control measures have been suggested for their management.
The Orthoptera are the most species‐rich group among the lower neopterans, and there is a tremendous amount of diversity in biology, ecology, and morphology in the order. This chapter presents a general overview of the systematics of the Orthoptera, as well as diversity in form and function in the order, and provides a brief synopsis of each of the known families. The most notable study was by Flook, who produced the first modern phylogeny of the Orthoptera, based on 31 in‐group taxa representing all major lineages and few ribosomal loci; they also reclassified some superfamilies. The monophyly of the Orthoptera has been supported by morphological and molecular data. The taxonomic classification of the Orthoptera has a tumultuous and complex history, as different taxonomists proposed conflicting classification schemes based on different character sets, such as fossil wing venation, internal organs, external morphology, and the male phallic complex.
Dealing with crisis situations involves significant collaborative decision-making to recover lives and preserve properties. In order to reach timely and appropriate decisions, crisis response organizations need to rapidly obtain an accurate situation awareness of the crisis context. A process by which they need to gather, access, and exchange near real-time information about the events circumstances throughout the entire crisis life cycle. Such activities imply a huge participation of collaborating organizations and goes even beyond their internal borders to reach the entire crisis-stricken community. Recent crisis and disaster situations have demonstrated the crucial role citizens can and must play in responding to such events. The growing development of advanced technologies has open the door for large public to be a key factor in making decisions and conducting guided response actions. We propose in this paper a comprehensive approach that integrates crisis crowdsourcing tasks and techniques to crisis decision-making activities. To demonstrate its relevance, we present a study of crisis scenario based on the context of Desert Locust Plague Survey and Control in the Algerian National Institute of Plant Protection (INPV).
Dichroplus maculipennis is one of the most damaging grasshopper species of Argentina. Individuals of this species at high density are historically known to show aggregation behavior and dispersal flights, attributes that might suggest that it does exhibit to some extent phase polyphenism in relation to population density. Phase polyphenism is a complex phenomenon and the amplitude of phase change is usually species-dependent. Morphological differences between gregarious and solitarious locusts can be measured and analyzed in order to characterize the phase status. The objective of this study was to evaluate morphometric differences between individuals of a D. maculipennis field population in the southern Pampas region of Argentina during non-outbreak and outbreak conditions including the magnitude of sexual size dimorphism related to variation in density. Collected individuals in the outbreak condition totaled 804 (422 females, 382 males) and those in non-outbreak condition were 325 (141 females, 184 males). Six morphometric characters were measured and two ratios (F/C and E/F) usually used to discriminate between solitarious and gregarious individuals in true locust species were calculated. Results show that size traits of D. maculipennis change over time at the population level, and that these changes correlate with outbreak vs non-outbreak populations. Females and males of D. maculipennis in outbreak conditions are significantly larger than in non-outbreak conditions. Furthermore, significant change over time was recorded in values of the two ratios calculated. D. maculipennis showed female biased sexual size dimorphism in both outbreak and non-outbreak conditions. There is a smaller difference in body size among females and males in outbreak conditions than in females and males in non-outbreak conditions. These results may be an indication of the presence of density-dependent phenotypic plasticity in this species, but additional experiments are required in order to establish a causal relationship between population density and changes in size traits.
Meco, J., Muhs, D.R., Fontugne, M., Ramos, A.J.G., Lomoschitz, A. & Patterson, D. 2010: Late Pliocene and Quaternary Eurasian locust infestations in the Canary Archipelago. Lethaia, Vol. 44, pp. 440–454.
The Canary Archipelago has long been a sensitive location to record climate changes of the past. Interbedded with its basalt lavas are marine deposits from the principal Pleistocene interglacials, as well as aeolian sands with intercalated palaeosols. The palaeosols contain African dust and innumerable relict egg pods of a temperate-region locust (cf. Dociostaurus maroccanusThunberg 1815). New ecological and stratigraphical information reveals the geological history of locust plagues (or infestations) and their palaeoclimatic significance. Here, we show that the first arrival of the plagues to the Canary Islands from Africa took place near the end of the Pliocene, ca. 3 Ma, and reappeared with immense strength during the middle Late Pleistocene preceding MIS (marine isotope stage) 11 (ca. 420 ka), MIS 5.5 (ca. 125 ka) and probably during other warm interglacials of the late Middle Pleistocene and the Late Pleistocene. During the Early Holocene, locust plagues may have coincided with a brief cool period in the current interglacial. Climatically, locust plagues on the Canaries are a link in the chain of full-glacial arid–cold climate (calcareous dunes), early interglacial arid–sub-humid climate (African dust inputs and locust plagues), peak interglacial warm–humid climate (marine deposits with Senegalese fauna), transitional arid–temperate climate (pedogenic calcretes), and again full-glacial arid–cold climate (calcareous dunes) oscillations. During the principal interglacials of the Pleistocene, the Canary Islands recorded the migrations of warm Senegalese marine faunas to the north, crossing latitudes in the Euro-African Atlantic. However, this northward marine faunal migration was preceded in the terrestrial realm by interglacial infestations of locusts. □Locust plagues, Canary Islands, Late Pliocene, Pleistocene, Holocene, palaeoclimatology.
Outbreaks of locusts cause enormous economic losses to agriculture in many countries. To develop environmentally friendly strategies for their control, much research has been focused on the factors that influence locust biology, particularly infochemical-mediated interactions. We present herein the identification and synthesis of both Z and E isomers of phytal (3,7,11,15-tetramethylhexadec-2-enal, 1), which are involved in chemical communication and behaviour of the Moroccan locust, Dociostaurus maroccanus, a serious agricultural pest. The compound was identified by comparison of its chromatographic and spectrometric features and microchemical reactions with those of a synthetic sample. The natural compound was shown to have the R,R configuration by chiral HPLC analysis, and its structure is unique as an insect pheromone component. Both isomers of phytal are produced by sexually mature adult males and elicit electroantennographic responses in antennae of both sexes. In two-choice olfactometer bioassays, males and females significantly preferred the stream enriched with racemic phytal to the control. In contrast, hydrogenated phytal was behaviourally inert. Both isomers of phytal are specific to D. maroccanus as they are absent in the closely related, habitat-sharing species Dociostaurus jagoi and Calliptamus wattenwylianus. Legs and wings are the main release sites of the compound: approximately 90 % of that emitted by living individuals. In biosynthetic studies, phytal appears to proceed from oxidation of phytol (2) after injection of deuterated phytol into the abdomen of the insect or after administration in the diet. Our results demonstrate that phytal is a candidate sex pheromone component of the Moroccan locust; it is produced by mature males, and might be eavesdropped upon by conspecific males.
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