Larval Movement Research Articles

Effects of plant micro-environment on movement of Helicoverpa armigera (Hübner) larvae and the relationship to a hierarchy of stimuli

Locomotory behaviour of 1st instar Helicoverpa armigera is influenced by a complex of micro-attributes, the leaf “environment”, comprising odours, wax chemistry, trichomes and grip texture. Larval movement speeds on leaves of different types varied more than eight fold. On garden pea, Pisum sativum, there is a hierarchy of stimuli perceived by larvae resulting in differing behavioural responses. Light and angle are paramount in responses to micro-environment. These influence responses to local stimuli. Experiments in darkness produce different responses from those under laboratory light. In darkness, on horizontal surfaces as found for most leaves, preference for leaf surface is driven by micro-environment associated with leaf waxes. Larvae prefer the abaxial surface. In light, on horizontal surfaces, larvae seek enclosed spaces and foray under leaf surfaces. They wander more openly in the dark. Such information is important in building a model of larval behaviour and predicting behaviour on differing plant architectures.

Toxicity and Residual Efficacy of Chlorantraniliprole, Spinetoram, and Emamectin Benzoate to Obliquebanded Leafroller (Lepidoptera: Tortricidae)

Studies were conducted to determine the residual toxicity of spinetoram, chlorantraniliprole, and emamectin benzoate to obliquebanded leafroller, Choristoneura rosaceana (Harris) (Lepidoptera: Tortricidae). Larvae were exposed to apple (Malus spp.) foliage collected at different intervals after an airblast sprayer application at the manufacturer-recommended field rate and half the field rate. A mortality of 100% was recorded at field rate applications of spinetoram, chlorantraniliprole, and emamectin benzoate through 59, 38, and 10 d after treatment (DAT), respectively. Significantly less foliage was consumed by C. rosaceana larvae surviving in the emamectin, chlorantraniliprole, and spinetoram treatments compared with those exposed to untreated foliage. Third-instar C. rosaceana exposed to fresh residues on terminal foliage showed 100% mortality after 5-d exposure to spinetoram residues and after 10-d exposure to chlorantraniliprole and emamectin benzoate. The effects of larval movement from foliage with fresh residues was examined by transferring neonate larvae from foliage treated with spinetoram, chlorantraniliprole, or emamectin benzoate to untreated foliage after various exposure intervals. An exposure of 1, 3, and 6 d was required for spinetoram, chlorantraniliprole, and emamectin benzoate to cause 100% mortality at the field rate, respectively. The higher the concentration of chlorantraniliprole and emamectin benzoate, the less exposure time was necessary to cause high levels of mortality in C. rosaceana neonates. Our results indicate that these novel insecticides are highly toxic to C. rosaceana larvae. Implications of these results for C. rosaceana management programs are discussed.

Bollworm (Lepidoptera: Noctuidae) Behavior on Transgenic Cotton Expressing Cry1Ac and Cry1F Proteins

Bollworm, Helicoverpa zea (Boddie), larvae are known to move away from Bollgard™ (Monsanto Co., St. Louis, MO) cotton terminals. Bollworm larvae are also found more frequently on flower buds (squares) and bolls of Bollgard as compared with those of nontransgenic cotton. However, data are not available for bollworm behavior on commercially available transgenic cotton varieties expressing 2 Bacillus thuringiensis Berliner proteins. Thus, field studies were conducted in Stoneville, MS, during 2007 and 2008 to determine whether bollworm behavior differed among cotton expressing the Cry1Ac and Cry1F proteins (Widestrike®, Phytogen 485, PhytoGen Seed Co., LLC, Indianapolis, IN) and nonBt cotton (Phytogen 425, PhytoGen Seed Co., LLC, Indianapolis, IN). Two-day-old bollworm larvae were placed into terminals of either individual cotton plants or plants within 1-m plots during the flowering period. Comparison of larval movement away from cotton terminals between Widestrike and nonBt plants did not differ at 3, 6, 24, or 48 h after infestation. In addition, larval distribution on fruiting structures did not differ between Widestrike and nonBt cotton. These data indicate that different scouting methods for bollworm larvae should be used for the various Bt cotton technologies commercially available.

Relationship of larval desiccation to Anopheles gambiae Giles and An. arabiensis Patton survival

Relationship of larval desiccation to Anopheles gambiae Giles and An. arabiensis Patton survival

The movement and distribution of Helicoverpa armigera (Hübner) larvae on pea plants is affected by egg placement and flowering.

The distribution and movement of 1st instar Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) larvae on whole garden pea (Pisum sativum L.) plants were determined in glasshouse trials. This economically-important herbivore attacks a wide variety of agricultural, horticultural and indigenous plants. To investigate the mechanisms underlying larval intra-plant movement, we used early-flowering and wild-type plant genotypes and placed eggs at different vertical heights within the plants, one egg per plant. Leaf water and nitrogen content and cuticle hardness were measured at the different plant heights. Of 92 individual larvae, 41% did not move from the node of eclosion, 49% moved upwards and 10% moved downwards with the distance moved being between zero and ten plant nodes. Larvae from eggs placed on the lower third of the plant left the natal leaf more often and moved further than larvae from eggs placed in the middle or upper thirds. The low nutritive value of leaves was the most likely explanation for more movement away from lower plant regions. Although larvae on flowering plants did not move further up or down than larvae on non-flowering plants, they more often departed the leaflet (within a leaf) where they eclosed. The final distribution of larvae was affected by plant genotype, with larvae on flowering plants found less often on leaflets and more often on stipules, tendrils and reproductive structures. Understanding intra-plant movement by herbivorous insects under natural conditions is important because such movement determines the value of economic loss to host crops. Knowing the behaviour underlying the spatial distribution of herbivores on plants will assist us to interpret field data and should lead to better informed pest management decisions.

Distribution and retention of Petrolisthes armatus in a coastal plain estuary: The role of vertical movement in larval transport

Since transport of planktonic larvae is essential to the maintenance and expansion of many marine species, we examined the spatial and temporal distribution of green porcelain crab Petrolisthes armatus (Gibbes, 1850) larvae and the possible underlying physical and behavioral mechanisms using a combination of field observations and numerical modeling. The field study consisted of observations of larval abundance and distribution as well as hydrographic surveys of the Satilla River estuary on the east coast of the USA in August 2006. Larvae were found throughout the water column within the tributaries but primarily at depth in the main river. A numerical model was used to examine the effect of flow and possible larval behavior responsible for the observed distribution and the consequences for larval retention in the estuary. Model results that included downward larval movement are consistent with the field observations, supporting the hypothesis that P. armatus larvae vertically migrate within the water column, which aids in their retention within the estuary.

Morphology–flow interactions lead to stage-selective vertical transport of larval sand dollars in shear flow

Many larvae and other plankton have complex and variable morphologies of unknown functional significance. We experimentally and theoretically investigated the functional consequences of the complex morphologies of larval sand dollars, Dendraster excentricus (Eschscholtz), for hydrodynamic interactions between swimming and turbulent water motion. Vertical shearing flows (horizontal gradients of vertical flow) tilt organisms with simple geometries (e.g. spheres, ellipsoids), causing these organisms to move horizontally towards downwelling water and compromising their abilities to swim upwards. A biomechanical model of corresponding hydrodynamic interactions between turbulence-induced shear and the morphologically complex four-, six- and eight-armed stages of sand dollar larvae suggests that the movements of larval morphologies differ quantitatively and qualitatively across stages and shear intensities: at shear levels typical of calm conditions in estuarine and coastal environments, all modeled larval stages moved upward. However, at higher shears, modeled four- and eight-armed larvae moved towards downwelling, whereas six-armed larvae moved towards upwelling. We also experimentally quantified larval movement by tracking larvae swimming in low-intensity shear while simultaneously mapping the surrounding flow fields. Four- and eight-armed larvae moved into downwelling water, but six-armed larvae did not. Both the model and experiments suggest that stage-dependent changes to larval morphology lead to differences in larval movement: four- and eight-armed stages are more prone than the six-armed stage to moving into downwelling water. Our results suggest a mechanism by which differences can arise in the vertical distribution among larval stages. The ability to mitigate or exploit hydrodynamic interactions with shear is a functional consequence that potentially shapes larval evolution and development.

Navigational Decision Making in Drosophila Thermotaxis

A mechanistic understanding of animal navigation requires quantitative assessment of the sensorimotor strategies used during navigation and quantitative assessment of how these strategies are regulated by cellular sensors. Here, we examine thermotactic behavior of the Drosophila melanogaster larva using a tracking microscope to study individual larval movements on defined temperature gradients. We discover that larval thermotaxis involves a larger repertoire of strategies than navigation in smaller organisms such as motile bacteria and Caenorhabditis elegans. Beyond regulating run length (i.e., biasing a random walk), the Drosophila melanogaster larva also regulates the size and direction of turns to achieve and maintain favorable orientations. Thus, the sharp turns in a larva's trajectory represent decision points for selecting new directions of forward movement. The larva uses the same strategies to move up temperature gradients during positive thermotaxis and to move down temperature gradients during negative thermotaxis. Disrupting positive thermotaxis by inactivating cold-sensitive neurons in the larva's terminal organ weakens all regulation of turning decisions, suggesting that information from one set of temperature sensors is used to regulate all aspects of turning decisions. The Drosophila melanogaster larva performs thermotaxis by biasing stochastic turning decisions on the basis of temporal variations in thermosensory input, thereby augmenting the likelihood of heading toward favorable temperatures at all times.

Slowdown promotes muscle integrity by modulating integrin-mediated adhesion at the myotendinous junction

The correct assembly of the myotendinous junction (MTJ) is crucial for proper muscle function. In Drosophila, this junction comprises hemi-adherens junctions that are formed upon arrival of muscles at their corresponding tendon cells. The MTJ mainly comprises muscle-specific alphaPS2betaPS integrin receptors and their tendon-derived extracellular matrix ligand Thrombospondin (Tsp). We report the identification and functional analysis of a novel tendon-derived secreted protein named Slowdown (Slow). Homozygous slow mutant larvae exhibit muscle or tendon rupture, sluggish larval movement, partial lethality, and the surviving adult flies are unable to fly. These defects result from improper assembly of the embryonic MTJ. In slow mutants, Tsp prematurely accumulates at muscle ends, the morphology of the muscle leading edge changes and the MTJ architecture is aberrant. Slow was found to form a protein complex with Tsp. This complex is biologically active and capable of altering the morphology and directionality of muscle ends. Our analysis implicates Slow as an essential component of the MTJ, crucial for ensuring muscle and tendon integrity during larval locomotion.

Modelling the transport of common sole larvae in the southern North Sea: Influence of hydrodynamics and larval vertical movements

In the present work we used a particle-tracking model coupled to a 3D hydrodynamic model to study the combined effect of hydrodynamic variability and active vertical movements on the transport of sole larvae in the southern North Sea. Larval transport from the 6 main spawning grounds was simulated during 40 day periods starting on 2 plausible spawning dates, the 15/04 and the 01/05, during 2 years, 1995 and 1996. In addition to a “passive” behaviour, 3 types of active vertical movements inspired from previous studies have been tested: (1) Eggs and early larvae float in the surface waters, late larvae migrate toward the bottom and stay there until the end of the simulation; (2 and 3) Eggs float in the surface waters, early larvae perform diel vertical migrations in the surface waters, and (2) Late larvae perform diel vertical migrations in the bottom waters until the end of the simulation; or (3) Late larvae perform tidally synchronised vertical migrations in the bottom waters until the end of the simulation. These behaviours have been implemented in the model with vertical migration rates, positive or negative, which can account for buoyancy or real swimming activity. Variations in larval transport were analysed in terms of mean trajectories, final larvae distribution, larval retention above nurseries, and connectivity. Results suggest that the variations in larval retention above nurseries due to the varying hydrodynamic conditions are not consistent in space i.e. not the same for all the spawning sites. The effect of active vertical movements on larval transport is also not consistent in space: Effects of active vertical movements include decreased retention above nurseries, decreased transport and/or decreased horizontal dispersion of larvae through reduced vertical shear (depending on the zone). The variability in larval retention due to hydrodynamic variability is higher than variability due to differences in the behaviour of larvae. In terms of connectivity, exchanges of larvae between the 6 areas considered are moderate: 10 connections happened out of the 30 possible, and the amount of larvae exchanged is much lower than the amount of larvae retained except in a few cases. This is not incompatible with the possible existence of subpopulations of sole in the Eastern Channel and southern North Sea.

Functional localization of neuronal components controlling larval peristaltic movements in Drosophila

Functional localization of neuronal components controlling larval peristaltic movements in Drosophila

Subunit-specific and homeostatic regulation of glutamate receptor localization by CaMKII in Drosophila neuromuscular junctions

For the efficient transfer of information across neural circuits, the number of synaptic components at synapses must be appropriately regulated. Here, we found that postsynaptic calcium/calmodulin dependent protein kinase II (CaMKII) modulates the localization of glutamate receptors (GluRs) at Drosophila larval neuromuscular junctions (NMJs). Expression of an inhibitory peptide of CaMKII, Ala, in muscle cells enhanced the density of GluRIIA, which is a major and calcium-permeable subunit of GluR, at synapses of third instar larval NMJs. On the other hand, postsynaptic expression of a constitutively active form of CaMKII (T287D) reduced synaptic GluRIIA. These results suggest that CaMKII regulates GluRIIA at NMJs. Moreover, postsynaptic expression of T287D abolished the accumulation of the scaffolding protein discs large (DLG) at synapses, while exerting no significant effects on the presynaptic area and the localization of cell adhesion molecule fasciclin II (FasII). The amplitude of excitatory junctional potentials (EJPs) was enhanced in Ala-expressing larvae, whereas it was unaffected in T287D-expressing larvae in spite of the prominent loss of GluRIIA. The amplitude of miniature EJPs (mEJPs) was significantly reduced and quantal content was significantly increased in T287D-expressing larvae. Notably, another class of GluR containing GluRIIB was enhanced by the postsynaptic expression of T287D. These results suggest that the homeostatic mechanism in T287D larvae works to maintain the level of synaptic responses. Thus, the Drosophila larval NMJs have several regulatory systems to ensure efficient muscle excitability which is necessary for proper larval movement.

Spinal Interneurons Differentiate Sequentially from Those Driving the Fastest Swimming Movements in Larval Zebrafish to Those Driving the Slowest Ones

Studies of neuronal networks have revealed few general principles that link patterns of development with later functional roles. While investigating the neural control of movements, we recently discovered a topographic map in the spinal cord of larval zebrafish that relates the position of motoneurons and interneurons to their order of recruitment during swimming. Here, we show that the map reflects an orderly pattern of differentiation of neurons driving different movements. First, we use high-speed filming to show that large-amplitude swimming movements with bending along much of the body appear first, with smaller, regional swimming movements emerging later. Next, using whole-cell patch recordings, we demonstrate that the excitatory circuits that drive large-amplitude, fast swimming movements at larval stages are present and functional early on in embryos. Finally, we systematically assess the orderly emergence of spinal circuits according to swimming speed using transgenic fish expressing the photoconvertible protein Kaede to track neuronal differentiation in vivo. We conclude that a simple principle governs the development of spinal networks in which the neurons driving the fastest, most powerful swimming in larvae develop first with ones that drive increasingly weaker and slower larval movements layered on over time. Because the neurons are arranged by time of differentiation in the spinal cord, the result is a topographic map that represents the speed/strength of movements at which neurons are recruited and the temporal emergence of networks. This pattern may represent a general feature of neuronal network development throughout the brain and spinal cord.

Marine reserve networks for species that move within a home range

Marine reserves are expected to benefit a wide range of species, but most models used to evaluate their effects assume that adults are sedentary, thereby potentially overestimating population persistence. Many nearshore marine organisms move within a home range as adults, and there is a need to understand the effects of this type of movement on reserve performance. We incorporated movement within a home range into a spatially explicit marine reserve model in order to assess the combined effects of adult and larval movement on persistence and yield in a general, strategic framework. We describe how the capacity of a population to persist decreased with increasing home range size in a manner that depended on whether the sedentary case was maintained by self persistence or network persistence. Self persistence declined gradually with increasing home range and larval dispersal distance, while network persistence decreased sharply to 0 above a threshold home range and was less dependent on larval dispersal distance. The maximum home range size protected by a reserve network increased with the fraction of coastline in reserves and decreasing exploitation rates outside reserves. Spillover due to movement within a home range contributed to yield moderately under certain conditions, although yield contributions were generally not as large as those from spillover due to larval dispersal. Our results indicate that, for species exhibiting home range behavior, persistence in a network of marine reserves may be more predictable than previously anticipated from models based solely on larval dispersal, in part due to better knowledge of home range sizes. Including movement within a home range can change persistence results significantly from those assuming that adults are sedentary; hence it is an important consideration in reserve design.

The role of two plant-derived volatiles in the foraging movement of 1st instar Helicoverpa armigera (Hübner): time to stop and smell the flowers

Positive phototaxis and negative geotaxis are behaviours that 1st instar Helicoverpa armigera use to direct their foraging movement upward towards nutritious new plant growth and reproductive structures. Odours emitted by fruits or seeds can attract larvae directly via chemotaxis. In this study we clarify the effect of leaf and flower odours on foraging 1st instar H. armigera. Using a Y-tube olfactometer we tested for chemotaxis towards two plant volatiles and found larvae were not attracted. Bioassays for phototaxis towards UV, blue, green and white light showed that a green leaf volatile ((Z)-3-hexenyl acetate) and a flower volatile (phenylacetaldehyde) reduced larval phototaxis towards blue light. Feeding on a host plant reduced phototaxis towards blue and green light. We concluded that the upward movement of 1st instars on plants is largely due to phototaxis towards the blue wavelengths of skylight. Plant attributes such as volatile chemicals affect the expression of phototaxis and therefore, indirectly influence larval movement to locate food resources.

Tomato-aphid-hoverfly: a tritrophic interaction incompatible for pest management

Trichome-based tomato resistance offers the potential to reduce pesticide use, but its compatibility with biological control remains poorly understood. We evaluated Episyrphus balteatus De Geer (Diptera, Syrphidae), an efficient aphidophagous predator, as a potential biological control agent of Myzus persicae Sulzer (Hemiptera, Aphididae) on trichome-bearing tomato cultivars. Episyrphus balteatus’ foraging and oviposition behavior, as well as larval mobility and aphid accessibility, were compared between two tomato cultivars (Lycopersicon esculentum Mill. ‘Moneymaker’ and ‘Roma’) and two other crop plants; broad bean (Vicia faba L.) and potato (Solanum tuberosum L.). Hoverfly adults landed and laid more eggs on broad beans than on three species of Solanaceae. Hoverfly larval movement was drastically reduced on tomato, and a high proportion of hoverfly larvae fell from the plant before reaching aphid prey. After quantifying trichome abundance on each of these four plants, we suggest that proprieties of the plant surface, specifically trichomes, are a key factor contributing to reduced efficacy of E. balteatus as a biological agent for aphid control on tomatoes.

Evaluating existing movement hypotheses in linear systems using larval stream salamanders

Because of their linear nature, streams provide a restrictive framework to understand the movement ecology of many animals. Stream movements have been characterized under two competing hypotheses. The colonization hypothesis dictates that small individuals experience passive drift, but concurrent, upstream movement by larger individuals replaces the loss of small individuals. Alternatively, the production hypothesis suggests that downstream movements are a consequence of limited resource availability. Previous research suggests that large larvae should move upstream and vice versa for small larvae, which should therefore be found downstream more often. We conducted a mark–recapture study of larval red salamanders ( Pseudotriton ruber (Sonnini de Manoncourt and Latreille, 1801)) to assess the validity of these hypotheses. We found that no larvae exhibited downstream movement (skew = 0.361, p = 0.019; biased upstream), and large larvae were the only size cohort to exhibit directional movement upstream (skew = 0.901, p = 0.035). Contrary to predictions under the colonization hypothesis, small larvae were found upstream more frequently than large larvae (N = 871, H = 16.29, df = 2, p < 0.001). Our results suggest that larval movements are related to abiotic stream conditions, and we conclude that neither hypothesis fully explains stream movement. In the absence of drift, new movement hypotheses are necessary to describe persistent upstream movement in streams. These hypotheses should consider individual causes of movement and the direction of movements that will improve the fitness of the organism.

A Shell of Its Former Self: CanOstrea luridaCarpenter 1864 Larval Shells Reveal Information About a Recruit's Birth Location?

Despite the interest in restoring remnant populations of the Olympia oyster, Ostrea lurida Carpenter 1864,† little is known about connectivity among populations. Identifying the sources of settling larvae could broaden our understanding of the degree to which particular populations are reliant on their neighbors for their persistence. Calcified structures such as the otoliths of fish and statoliths of invertebrates are increasingly being exploited as useful ''natural tags'' that help track individual movements and, when applicable to larvae, could help to pinpoint important source populations. In controlled laboratory culturing experiments, we explored the prospects for using the chemistry of larval shells (prodissoconchs) as natural tags of larval source by examining whether larval shells record shifts in seawater element chemistry, whether larval shells undergo ontogenetic shifts in element uptake, and whether the chemistry of the shell formed during brooding is compromised by subsequent shell thickening during the planktonic phase. Results from a two-way ANOVA examining the effect of seawater element concentration and ontogeny showed that element/ Ca in the shell increased in response to increasing seawater elemental concentrations for Ba, Ce, Pb, and Mn, whereas shell Cu/Ca did not change. Ostrea lurida shell chemistry also showed strong ontogenetic shifts in element/Ca for Mg, Sr, and Cu during the transition from larva to settler. Settler shell Mg/Ca strongly increased compared with planktonic shell, whereas Sr/Ca and Cu/Ca showed the opposite pattern. Further, the chemistry of the shell formed during brooding (at the birth location) did change as a function of environmental conditions experienced during the planktonic phase for the elements Ba and Ce, but that change was limited to regions of the brooded shell just adjacent to the planktonic shell. When the brooded portions of larval shells were sampled closer to the umbo, the brooded shells chemistry remains intact. The combined results suggest that larval Ostrea lurida shells act as recorders of environmental change and show promise as tools to track larval movements.

Opposing Aminergic Modulation of Distinct Spinal Locomotor Circuits and Their Functional Coupling during Amphibian Metamorphosis

The biogenic amines serotonin (5-HT) and noradrenaline (NA) are well known modulators of central pattern-generating networks responsible for vertebrate locomotion. Here we have explored monoaminergic modulation of the spinal circuits that generate two distinct modes of locomotion in the metamorphosing frog Xenopus laevis. At metamorphic climax when propulsion is achieved by undulatory larval tail movements and/or by kicking of the newly developed adult hindlimbs, the underlying motor networks remain spontaneously active in vitro, producing either separate fast axial and slow appendicular rhythms or a single combined rhythm that drives coordinated tail-based and limb-based swimming in vivo. In isolated spinal cords already expressing distinct axial and limb rhythms, bath-applied 5-HT induced coupled network activity through an opposite slowing of axial rhythmicity (by increasing motoneuron burst and cycle durations) and an acceleration of limb rhythmicity (by decreasing burst and cycle durations). In contrast, in preparations spontaneously expressing coordinated fictive locomotion, exogenous NA caused a dissociation of spinal activity into separate faster axial and slower appendicular rhythms by decreasing and increasing burst and cycle durations, respectively. Moreover, in preparations from premetamorphic and postmetamorphic animals that express exclusively axial-based or limb-based locomotion, 5-HT and NA modified the developmentally independent rhythms in a similar manner to the amines' opposing effects on the coexisting circuits at metamorphic climax. Thus, by exerting differential modulatory actions on one network that are opposite to their influences on a second adjacent circuit, these two amines are able to precisely regulate the functional relationship between different rhythmogenic networks in a developing vertebrate's spinal cord.

Behaviour and ecology of the western corn rootworm (Diabrotica virgifera virgifera LeConte)

Abstract1 The western corn rootworm (WCR) is a historic pest with a legacy of resistance and behavioural plasticity. Its behaviour and nutritional ecology are important to rootworm management. The success of the most effective and environmentally benign rootworm management method, annual crop rotation, was based on an understanding of rootworm behaviour and host–plant relationships. Enthusiastic adoption of crop rotation, provided excellent rootworm management, but also selected for behavioural resistance to this cultural control.2 Though well‐studied, significant gaps in WCR biology remain. Understanding the topics reviewed here (mating behaviour, nutritional ecology, larval and adult movement, oviposition, alternate host use, and chemical ecology) is a starting point for adapting integrated pest management and insect resistance management (IRM) to an expanding WCR threat. A presentation of significant questions and areas in need of further study follow each topic.3 The expansion of WCR populations into Europe exposes this pest to new environmental and regulatory conditions that may influence its behaviour and ecology. Reviewing the state of current knowledge provides a starting point of reference for researchers and pest management decision‐makers in North America and Europe.4 The trend toward increasing adoption of transgenic maize will place an increasing premium on understanding WCR behaviour. IRM plans designed to promote sustainable deployment of transgenic hybrids are grounded on assumptions about WCR movement, mating and ovipositional behaviour. Preserving the utility of new and old management options will continue to depend on a thorough understanding of WCR biology, even as the ecological circumstances and geography of WCR problems become more complex.