Australian Plague Locust Chortoicetes Terminifera Research Articles

Seeing the locust in the swarm: accounting for spatiotemporal hierarchy improves ecological models of insect populations

Ecological phenomena operate at different spatial scales and are not uniform across landscapes or through time. One ecological theory that attempts to account for scaling and spatiotemporal variances is hierarchical patch dynamics. It introduces a hierarchical patch network with smaller spatiotemporal scales being nested within larger scales. However, few studies have modeled its presence within animal population dynamics. Locusts are an excellent model for investigating the spatiotemporal hierarchy of animal population dynamics, due to their high migratory capacity, large geographic ranges that extend across widely differing environments, and available long‐term data on distributions. Here, we investigated the influence of preceding vegetation growth on desert locust Schistocerca gregaria and Australian plague locust Chortoicetes terminifera outbreaks on three spatial levels (species range > geographic region > land unit) and between seasons. Both species are dryland herbivores with population dynamics linked to habitat productivity pulses after rain. We used NDVI data (MODIS imagery) as a measure of vegetation growth in hierarchical generalized additive models at different scales. Locust outbreaks were either preceded by vegetation growth between 78 and 32 days (Australian plague locusts) or 32 and 20 days before (desert locust) the observation. Although prior vegetation growth characterized outbreaks of both species, the temporal pattern of NDVI differed between spatiotemporal levels. All model selection criteria selected for a similar spatial hierarchy for both species: geographic region > land unit which supports the hierarchical patch dynamics paradigm. Further, it illuminates important timing differences between geographic regions and land units for preceding vegetation growth and locust outbreaks which can help locust managers identify when and where outbreaks occur. By acknowledging the spatiotemporal patterning of locust abundance, we account for heterogeneity of population dynamics throughout species ranges. Our findings demonstrate the importance of incorporating spatiotemporal variation in population models of insects and other animals.

Body condition constrains immune function in field populations of female Australian plague locust Chortoicetes terminifera.

The insect innate immune system comprises both humoral and cellular defence responses. In the laboratory, the insect immune system is well characterized. In the field, however, little is known about the role of constitutive insect immune function and how it varies within and between populations. Laboratory studies suggest that host nutrition has significant impact upon insect immune function. Thus, the rationale for this study was to sample natural populations of the Australian Plague Locust Chortoicetes terminifera to establish whether locust body condition (as determined by protein and lipid content) impacted their constitutive immune system and, as a result, has the potential to impact on their capacity to respond to a pathogenic challenge. We found that body condition varied greatly between individual female locusts within sites and that haemolymph protein levels, but not body lipid content, varied between sites. Moreover, our measures of immune function were correlated with the haemolymph levels of protein (in the case of haemocyte density), lipid (prophenoloxidase activity) or both (lysozyme-like antimicrobial activity). We discuss the implications of these findings for the role of biological pesticides in the control of locust populations.

Embryonic diapause in the Australian plague locust relative to parental experience of cumulative photophase decline

The Australian plague locust Chortoicetes terminifera (Walker) exhibits facultative embryonic diapause during autumn. To approximate natural photoperiod changes during late summer and autumn, locust nymphs were reared under different total declines in laboratory photophase (−0.5, −0.75, −1.0, −1.25, −1.5, −1.75, −2h each lowered in 15min steps) in a 24h photoperiod to quantify any effect on the subsequent production of diapause eggs. Induction of diapause eggs was significantly affected by accumulated photoperiod decline experienced by the parental generation throughout all development stages from mid-instar nymph to fledgling adult. The incidence of embryonic diapause ranged from nil at −0.5h to 86.6% diapause at −2h. Continued declines in photoperiod for post-teneral locusts (transitioned from −1h until fledging to −1.75h) produced a further increase in the proportion of diapause eggs. The results were unaffected by time spent at any given photoperiod, despite a previously indicated maximal inductive photoperiod of 13.5h being used as the mid-point of all treatments. Implications for the seasonal timing processes of photoperiodism in C. terminifera, which has a high migratory capacity and a latitudinal cline in the timing of diapause egg production across a broad geographic range, are discussed.

Parasitism of Eggs of the Australian Plague Locust Chortoicetes terminifera (Walker) (Orthoptera: Acrididae) by Scelio fulgidus Crawford (Hymenoptera: Scelionidae)

In eastern Australia, parasitism of eggs of the Australian plague locust, Chortoicetesterminifera (Walker) by the wasp Scelio fulgidus Crawford was surveyed between 1975 and 1994. In the arid interior, where most plagues of C. terminifera originate, parasitism was moderate to high (15-45% of eggpods), yet locusts increased to plague proportions in spite of parasitism. The consistently moderate parasitism of C. terminifera in the interior, in spite of its low rainfall, is a result of S. fulgidus development being well synchronized with that of its host. *After several generations in the interior, C. terminifera typically migrated from the interior to sub-coastal agricultural areas. When locusts invaded agricultural areas during summer, parasitism was only slightly lower than that in the interior, though parasitism declined between summer and autumn. Often the locust population in agricultural areas collapsed before the next summer and parasitism was very high in the eggpods of remnant locusts. The high post-outbreak parasitism levels were not reached during 1990-94, when a preventative control program kept locust populations from reaching plague proportions: lower host numbers mean a lower absolute abundance of S. fulgidus, so that when host populations collapsed, the parasitism in residual locust populations increased less. [

Insect Migration: Tracking Resources through Space and Time.

Part I. Insect Migration in Relation to Weather and Climate: 1. Long-range insect migration in relation to climate and weather: Africa and Europe D. E. Pedgley, D. R. Reynolds and G. M. Tatchell 2. Insect migration in North America: synoptic-scale transport in a highly seasonal environment S. J. Johnson 3. Migration of the brown planthopper Nilaparvata lugens and the white-backed planthopper Sogatella furcifera in East Asia: the role of weather and climate R. Kisimoto and K. Sogawa 4. Migration of the oriental armyworm Mythimna separata in East Asia in relation to weather and climate. I. Northeastern China R. -L. Chen, Y. -J Sun, S. -Y. Wang, B. -P. Zhai and X. -Y. Bao 5. Migration of the oriental armyworm Mythimna separata in East Asia in relation to weather and climate. II. Korea J. -H. Lee and K. -B. Uhm 6. Migration of the oriental armyworm Mythimna separata in East Asia in relation to weather and climate. III. Japan K. Hirai 7. Insect migration in an arid continent. I. The common armyworm Mythimna convecta in eastern Australia G. McDonald 8. Insect migration in an arid continent. II. Helicoverpa spp. in eastern Australia P. C. Gregg, G. P. Fitt, M. P. Zalucki and D. A. H. Murray 9. Insect migration in an arid continent. III. The Australian Plague Locust Chortoicetes terminifera and the native budworm Helicoverpa punctigera in Western Australia K. J. Walden Part II. Adaptions for Migration: 10. Migratory potential in insects: variation in an uncertain environment A. G. Gatehouse and X. -X. Zhang 11. Insect migration in heterogeneous environments K. Wilson 12. The regulation of migration in Helicoverpa armigera J. Colvin 13. Physiological integration of migration in Lepidoptera J. N. McNeil, M. Cusson, J. Delisle, I. Orchard and S. S. Tobe 14. Aerodynamics, energetics and reproductive constraints of migratory flight in insects R. Dudley Part III. Forecasting Migrant Pests: 15. Operational aspects of forecasting migrant insect pests R. K. Day and J. D. Knight 16. Geographic information systems and remotely sensed data for determining the seasonal distribution of habitats of migrant insect pests T. P. Robinson 17. Forecasting systems for migrant pests. I. The brown planthopper Nilaparvata lugens in China B. -H. Zhou, H. -K. Wang and X. -N. Cheng 18. Forecasting systems for migrant pests. II. The rice planthoppers Nilaparvata lugens and Sogatella furcifera in Japan T. Watanabe 19. Forecasting systems for migrant pests. III. Locusts and grasshoppers in West Africa and Madagascar M. Lecoq Part IV. Overview and Synthesis: 20. Forecasting migrant insect pests J. I. Magor 21. Insect migration: a holistic conceptual model V. A. Drake, A. G. Gatehouse and R. A. Farrow Index.

Natural Selection and the Maintenance of Colour Pattern Polymorphism in the Australian Plague Locust Chortoicetes terminifera

Twelve samples of C. termini/era from seven locations in eastern Australia were analysed for colour pattern polymorphism. Although there was heterogeneity between the samples the overall frequencies of the colour pattern genotypes were very similar. Males and females showed consistent differences in their genotype frequencies and this is presumed to reflect differential selection between the two sexes. A comparison between observed genotype frequencies and those expected under random mating and in the absence of selection revealed large differences. In particular, genotypes heterozygous for two dominant genes were consistently underrepresented. While these differences could result from non-random mating it is argued that they are more likely to be due to viability differences between the genotypes.

The role of pressure in controlling the entry of water into the developing eggs of the Australian plague locust Chortoicetes terminifera (Walker)

AbstractThe normal internal hydrostatic pressure and the additional pressure necessary to rupture the egg shell was measured in the eggs of Chortoicetes terminifera, Newly laid white eggs burst at c 0.15 kg cm‐2, but after external tanning the chorion withstands c 0.5 kg cm‐2 when removed from its tanned foam ‘corset’ and 1.0 kg cm‐2 if left embedded in the egg pod material. Older eggs with formed cuticles often withstand 2.0 kg cm‐2 but yield at rather lower pressures if they develop ‘pin‐holes’. As the OP of the egg contents always exceeds 7.7 kg cm‐2 the rigidity of the wall is clearly insufficient to permit the generation of high hydrostatic pressures capable of preventing water entry during the non‐absorbing phases of development. Real hydrostatic pressures are lower than 0.06 kg cm‐2 in the young intact egg and reach only c 0.5 and 0.3 kg cm‐2, respectively, during the absorptive and post‐absorptive phases of development.Several events contribute to the sigmoid form of the water uptake curve. Water is at first excluded by a permeability barrier associated with the chorion. Absorption is delayed until the yolk is completely enclosed by the serosal cell layer. After undergoing cleavage, the yolk is then rapidly mobilized to furnish precursors for cuticle synthesis; in consequence, the internal OP rises from δ 0.76d̀K to 0.93d̀K despite the massive inflow of water which is governed by the osmotic gradient. At blastokinesis the serosa becomes detached from the cuticle; cuticle deposition and yolk mobilization are halted, the OP falling rapidly to cδT 0.53d̀K. The bulk entry of water then ceases. Any excessive hydrostatic pressures which develop later are relieved by the formation of self‐sealing ‘pin‐holes’.

Observations on the Feeding Activity of the Australian Plague Locust Chortoicetes terminifera (Walker) in Field Populations in Eastern Australia

Observations on the Feeding Activity of the Australian Plague Locust Chortoicetes terminifera (Walker) in Field Populations in Eastern Australia

On the abundance of the Australian plague locust Chortoicetes terminifera (Walker) in relation to the presence of trees

By the use of belt transects through selected tree stands, in the Bogan–Macquarie Outbreak Area of Chortoicetes terminifera (Walker), it was possible to show quantitatively that the abundance of non-swarming locusts is greatly limited by the presence of trees. Thus, if the former community dominants were re-established in those outbreak centres which were originally densely timbered, the production of swarms in them would probably be prevented, and locust damage thereby reduced. It was found that the abundance of adult locusts with in tree stands is not related to tree density, as such, but to a "barrier effect" of trees in depth, acting in such a way as to diminish the chances that an individual will penetrate to a given depth in the stand as that depth is increased. Hoppers (predominantly 4th instar), the non-swarming residue of bands hatching outside tree stands, appear to be similarly affected. On the other hand, the population density of hoppers hatching within stands, both at the time of hatching and when the majority reach the 4th instar, is correlated with tree density as well as with distance within the stand, suggesting that adult female locusts are influenced hy tree density in their selection of oviposition sites. The effect of tree density, as such, on the density distribution of locusts apparently disappears gradually as locusts grow and become increasingly mobile, because after they reach the adult stage the relationship no longer exists. The evidence obtained suggests that the limiting effect of trees on locust abundance is largely due to the reduction of light intensity that they bring about, the insects being affected per medium of their positive phototactic response.