In Southeast Asian tropical rainforests, two events, severe droughts associated with the El Niño-Southern Oscillation and general flowering, a type of community-wide mass flowering, occur at irregular, supra-annual intervals. The relationship between these two supra-annual events and patterns of insect population fluctuations has yet to be clearly elucidated. Leaf beetles (Chrysomelidae) are major herbivores and flower-visitors of canopy trees, affecting their growth and reproduction and, in turn, affected by tree phenology; but their population fluctuations in the Southeast Asian tropics have not been extensively investigated. We examined population fluctuation patterns of the 34 most dominant chrysomelid species in relation to the two supra-annual events by conducting monthly light-trapping over seven years in a lowland dipterocarp forest in Borneo. Our results showed large community variation in population fluctuation patterns and a supra-annual (between-year) variation in abundance for most of the dominant chrysomelids that was significantly larger than the annual (within-year) variation. Specifically, in response to a severe drought in 1998, chrysomelid species exhibited different population responses. These results show that population fluctuations of individual species, rather than the entire assemblage, must be analyzed to determine the effects of changes in environmental conditions on the structure of insect assemblages in the tropics, especially in regions where supra-annual environmental changes are relatively more important than seasonal changes.

Bemisia tabaci, biotype B, commonly known as the silverleaf whitefly (SLW) is an alien species that invaded Australia in the mid-90s. This paper reports on the invasion ecology of SLW and the factors that are likely to have contributed to the first outbreak of this major pest in an Australian cotton cropping system. Population dynamics of SLW within whitefly-susceptible crop (cotton and cucurbit) and non-crop vegetation (sowthistle, Sonchus spp.) components of the cropping system were investigated over four consecutive growing seasons (September–June) 2001/02–2004/05 in the Emerald Irrigation Area (EIA) of Queensland, Australia. Based on fixed geo-referenced sampling sites, variation in spatial and temporal abundance of SLW within each system component was quantified to provide baseline data for the development of ecologically sustainable pest management strategies. Parasitism of large (3rd and 4th instars) SLW nymphs by native aphelinid wasps was quantified to determine the potential for natural control of SLW populations. Following the initial outbreak in 2001/02, SLW abundance declined and stabilised over the next three seasons. The population dynamics of SLW is characterised by inter-seasonal population cycling between the non-crop (weed) and cotton components of the EIA cropping system. Cotton was the largest sink for and source of SLW during the study period. Over-wintering populations dispersed from weed host plant sources to cotton in spring followed by a reverse dispersal in late summer and autumn to broad-leaved crops and weeds. A basic spatial source-sink analysis showed that SLW adult and nymph densities were higher in cotton fields that were closer to over-wintering weed sources throughout spring than in fields that were further away. Cucurbit fields were not significant sources of SLW and did not appear to contribute significantly to the regional population dynamics of the pest. Substantial parasitism of nymphal stages throughout the study period indicates that native parasitoid species and other natural enemies are important sources of SLW mortality in Australian cotton production systems. Weather conditions and use of broad-spectrum insecticides for pest control are implicated in the initial outbreak and on-going pest status of SLW in the region.

The massive adoption of Bt cotton throughout China has been accompanied by outbreaks of secondary pests such as Adelphocoris spp. (Heteroptera: Miridae). The Adelphocoris group primarily consists of three species: A. suturalis, A. fasciaticollis and A. lineolatus, which greatly differ in geographical distribution and seasonal dynamics. However, the underlying drivers of these differences remain to be understood. The study of flight behaviour of these three species can yield important insight into their spatial and temporal dynamics and help explain their distribution. We examined flight propensity of the three Adelphocoris spp. under a range of biological and environmental conditions using a computer-monitored flight-mill. Gender and mating status only had minor effects on flight performance in these species, while age exerted great effects on it. Flight capacity was low for one-day-old adults and increased with age until day 10–13, then gradually decreased afterwards. Temperature and relative humidity affected flight propensity, with 20–23°C and 64–68% RH considered optimal for flight of all three species. Between-species comparisons indicated that A. suturalis and A. fasciaticollis had similar flight distance and duration, which were significantly greater than for A. lineolatus. Our findings provide crucial information for understanding geographical distribution and seasonal occurrence and for developing regional forecasting and pest management protocols for Adelphocoris species.

Tympanal hearing organs are widely used by insects to detect sound pressure. Such ears are relatively uncommon in the order Diptera, having only been reported in two families thus far. This study describes the general anatomical organization and experimentally examines the mechanical resonant properties of an unusual membranous structure situated on the ventral prothorax of the tsetse fly, Glossina morsitans (Diptera: Glossinidae). Anatomically, the prosternal membrane is backed by an air filled chamber and attaches to a pair of sensory chordotonal organs. Mechanically, the membrane shows a broad resonance around 5.3–7.2 kHz. Unlike previously reported dipteran tympana, a directional response to sound was not found in G. morsitans. Collectively, the morphology, the resonant properties and acoustic sensitivity of the tsetse prothorax are consistent with those of the tympanal hearing organs in Ormia sp. and Emblemasoma sp. (Tachinidae and Sarcophagidae). The production of sound by several species of tsetse flies has been repeatedly documented. Yet, clear behavioural evidence for acoustic behaviour is sparse and inconclusive. Together with sound production, the presence of an ear-like structure raises the enticing possibility of auditory communication in tsetse flies and renews interest in the sensory biology of these medically important insects.

Ecological communities used in biological pest control are usually represented as three-trophic level food chains with top-down control. However, at least two factors complicate this simple way of characterizing agricultural communities. First, agro-ecosystems are composed of several interacting species forming complicated food webs. Second, the structure of agricultural communities may vary in time. Efficient pest management approaches need to integrate these two factors to generate better predictions for pest control. In this work, we identified the food web components of an avocado agro-ecosystem, and unravelled patterns of co-occurrence and interactions between these components through field and laboratory experiments. This allowed us to predict community changes that would improve the performance of the naturally occurring predators and to test these predictions in field population experiments. Field surveys revealed that the food-web structure and species composition of the avocado community changed in time. In spring, the community was characterized by a linear food chain of Euseius stipulatus, an omnivorous mite, feeding on pollen. In the summer, E. stipulatus and a predatory mite, Neoseiulus californicus, shared a herbivorous mite prey. Laboratory experiments confirmed these trophic interactions and revealed that N. californicus can feed inside the prey nests, whereas E. stipulatus cannot, which may further reduce competition among predators. Finally, we artificially increased the coexistence of the two communities via addition of the non-herbivore food source (pollen) for the omnivore. This led to an increase in predator numbers and reduced populations of the herbivore. Therefore, the presence of pollen is expected to improve pest control in this system.

Social insects are among the world's most successful species at invading of new habitats. A good example of this invasive ability is Reticulitermes (Rhinotermitidae), a prominent group of subterranean termites. As a result of human intervention, i.e. transportation and creation of urban heat islands, Reticulitermes have been able to invade and thrive in cities located in areas where the natural habitat is normally too cold for colonization. They commonly infest man-made structures where they can cause extensive damage.

This study was designed to evaluate the invasiveness of Reticulitermes urbis that was probably introduced in France from the Balkans. Invasive potential was assessed on the basis of features typical to invasive social insects, i.e. unicoloniality, low intraspecific aggression, high level of polygyny and colony reproduction by budding. The opportunity to study establishment and spreading processes arose after extensive sampling of an imported Reticulitermes urbis population was performed over the entire city of Domène, France (Rhône-Alpes region).

For the first time, genetic analysis showed that the termites belonged to a single ‘genetic entity’ forming a vast colony covering about seven hectares. The colony was structured as an extended family with separate reproductive centres. We speculate that termites were introduced in a single location from which they gradually budded throughout the old town. Based on the absence of aggression among different nests within the colony, we defined this ‘genetic entity’ as a supercolony.

Dactylopius tomentosus (Lamarck) (Hemiptera: Dactylopiidae) is a cochineal insect whose host range is restricted to Cylindropuntia species (Caryophyllales: Cactaceae). This insect has been utilized successfully for biological control of Cylindropuntia imbricata (Haw.) F.M. Knuth in Australia and South Africa. Despite this, its biology has not been studied previously, probably due to the widely held belief that the biology of all Dactylopius species is similar. This study investigated the life cycle and the morphological and reproductive characteristics of D. tomentosus. Results revealed some unique characteristics of D. tomentosus: (i) eggs undergo a much longer incubation period, an average of 17 days compared to <1 day in its congeners; (ii) eggs are laid singly but are retained as an egg mass secured in a mesh of waxy threads attached to the female; (iii) the developmental times of males and females are longer compared to other Dactylopius spp. due to a longer egg incubation period; (iv) D. tomentosus does not undergo parthenogenesis; (v) D. tomentosus is smaller in size than its congeners; and (vi) male mating capacity and reproductive potential were both high and variable between males. There was a significant, strong, positive relationship (r=0.93) between female mass and fecundity, whereas the relationship between the number of females mated per male that became gravid and their fecundity was negative (r=−0.68). Besides contributing to our knowledge of this economically important species, the finding of unique characteristics of D. tomentosus biology underlines the need to study each species in this genus.

Integrated pest management strategies for cereal processing facilities often include both pheromone-baited pitfall traps and crack and crevice applications of a residual insecticide such as the pyrethroid cyfluthrin. In replicated pilot-scale warehouses, a 15-week-long experiment was conducted comparing population trends suggested by insect captures in pheromone-baited traps to direct estimates obtained by sampling the food patches in untreated and cyfluthrin-treated warehouses. Warehouses were treated, provisioned with food patches and then infested with all life stages of Tribolium castaneum (Herbst). Food patches, both those initially infested and additional uninfested, were surrounded by cyfluthrin bands to evaluate if insects would cross the bands. Results show that insect captures correlated with population trends determined by direct product samples in the untreated warehouses, but not the cyfluthrin-treated warehouses. However, dead insects recovered from the floor correlated with the insect densities observed with direct samples in the cyfluthrin-treated warehouses. Initially, uninfested food patches were exploited immediately and after six weeks harbored similar infestation densities to the initially infested food patches. These data show that pest management professionals relying on insect captures in pheromone-baited traps in cyfluthrin-treated structures could be deceived into believing that a residual insecticide application was suppressing population growth, when the population was actually increasing at the same rate as an untreated population.

Invasive plants have been shown to negatively affect the diversity of plant communities. However, little is known about the effect of invasive plants on the diversity at other trophic levels. In this study, we examine the per capita effects of two invasive plants, purple loosestrife (Lythrum salicaria) and reed canary grass (Phalaris arundinacea), on moth diversity in wetland communities at 20 sites in the Pacific Northwest, USA. Prior studies document that increasing abundance of these two plant species decreases the diversity of plant communities. We predicted that this reduction in plant diversity would result in reduced herbivore diversity. Four measurements were used to quantify diversity: species richness (S), community evenness (J), Brillouin's index (H) and Simpson's index (D). We identified 162 plant species and 156 moth species across the 20 wetland sites. The number of moth species was positively correlated with the number of plant species. In addition, invasive plant abundance was negatively correlated with species richness of the moth community (linear relationship), and the effect was similar for both invasive plant species. However, no relationship was found between invasive plant abundance and the three other measures of moth diversity (J, H, D) which included moth abundance in their calculation. We conclude that species richness within, and among, trophic levels is adversely affected by these two invasive wetland plant species.

Same-shape distribution model and rate summation approach are widely used to describe the insect developmental process. In this approach, by integrating a nonlinear deterministic developmental rate model and a probabilistic same-shape distribution model, the proportion of the cohort completing development is quantified as a function of accumulating developmental rates, which themselves are temperature dependent. This method is considered to be more accurate in modelling insect phenology because it can address a well-known biological fact, individual variability, that insect individual developmental rates respond to temperature differently, and because rate-summation essentially simulates developmental rates under variable temperatures instead of constant temperatures. By comparing insect development and reproduction with respect to their responses to temperatures, we argue for the extension of the same-shape and rate-summation approaches to modelling insect reproduction process under variable temperatures. We justify our arguments by the fact that individual variation universally exists in almost all biological characteristics, and the phenomenon that insect development and reproduction respond to temperature very similarly, which is supported by some endocrinological evidences reported in literature. In addition, the approach for testing the applicability of the original same-shape developmental modelling, experimentally verifying the sameness of the same-shape curves or that the shape of the curves is invariant with respect to the temperature regimes, equally applies to our extended version for reproduction modelling. We successfully tested the extension and its applicability with our experimental data of 1800 Russian wheat aphids' (RWA) (Diuraphis noxia (Mordvilko)) reproduction under various temperature and plant growth stage regimes. We also extended Taylor's (1981) nonlinear model for insect development to describe RWA mean (median) nymphal production under different temperatures and barley plant growth stages. Three same-shape distribution models, Weibull distribution, Stinner's model and logistic model, are used to construct the same-shape reproduction distribution models for RWA. The extensions performed in this paper contribute a new modelling approach for predicting insect reproduction under field variable temperatures and plant growth stages. The prediction model can be parameterized with data from typical laboratory demography experiments and further integrated into simulation models for insect population dynamics. Finally, we discussed why the sameness test of the same-shape distribution curves is sufficient in validating the approach and proposed a strategy for dealing with exceptional cases where the sameness test fails.

There is a severe shortage of knowledge of bee biogeography. Some former studies have highlighted a link between bee diversity and xeric ecosystems, but we know practically nothing of the macro-ecological factors driving bee diversity. The present study aims to analyse the main macro-ecological factors driving bee species-richness in the Saharan region. Our dataset includes 25,000+ records for localities in Africa, between 37° and 10°N. Maps and GIS were used to get a first overview of the distribution of the studied taxa. Partial least squares analysis (PLS) was used to study the impact of a set of ecological factors on the bee species richness (SR). The mapping highlighted the clustering of the highest bee SR values in some parts of the Saharan area (e.g. Maghreb, western Africa). In Central Sahara, there is an obvious topological coincidence of the high SR, the local mountain chains and the inland waters. The PLS helped to quantify the relationships between bee SR and a set of eco-climatic variables. It also highlighted a residual variance not explained by the considered descriptors. Our results recover the tight link between bee SR and xeric ecosystems. They also suggest that, within these ecosystems, bee SR is driven by an optimum of the energy-water balance (on which adjustment is allowed by the above gradients).

Subterranean termites (Reticulitermes grassei) were surveyed over successive seasons in a managed eucalyptus plantation in southeastern Portugal for 26 months. Termite activity in seven diameter categories of lying dead wood was investigated by a modified line intersection method (LIS). Each item sampled was inspected and assessed for termite attack and for general (i.e. fungal) decay status using standard protocols. Line intersection is quantitative to the extent that it can link foraging and decay parameters to woody biovolume. It was found that termites selected items with larger diameter, the observed trend showing an exponential character with greater termite attack as diameter increased. Attack by termites was positively associated with prior decay by fungi. A clear positive relationship was shown between rainfall and total woody biovolume containing live termites, underlining the importance of moisture for termite activity. Subterranean termites appeared to be important wood decomposers in the woodland studied, with an average of 30% of lying dead wood branches showing signs of termite attack.

Omnivory involves numerous feeding relationships and a complex web of interactions. When using omnivores in biocontrol, these interactions need to be understood to maximize feeding on the target species and minimize non-target interactions. Dicyphus hesperus is used along with Encarsia formosa for biocontrol of whiteflies in greenhouse tomato crops. Dicyphus hesperus is a generalist omnivore which feeds on all components of the system. To quantify these interactions, stable isotope analysis was used to identify trophic position with nitrogen isotopes (δ15N) and plant sources with carbon isotopes (δ13C). Feeding trials were used to establish baseline isotopic data for D. hesperus and their diet, including Verbascum thapsus, an alternative plant food. Cage trials were used to monitor population abundances and the isotopic signature of D. hesperus. In feeding trials, D. hesperus were enriched relative to their food, suggesting an elevated trophic position. However, large amounts of isotopic variation were found within all diet components, with only V. thapsus exhibiting a distinct signature. In cage trials, the average δ15N and δ13C of the omnivore declined over time, coinciding with declines in total available prey, though it may be confounded by changes in temperature. The range of δ13C, but not the range of δ15N, also declined over time. This suggests a change in the plant source within the diet, but also some unquantified variability within the population. We suggest that diet variability exists within D. hesperus populations, declining as prey become less abundant.

A Belgian field strain (MR-VP) of Tetranychus urticae (Koch) (Acari: Tetranychidae) exhibits different levels of resistance to four frequently used METI (mitochondrial electron transport inhibitor)-acaricides, i.e. tebufenpyrad, fenpyroximate, pyridaben and fenazaquin. Resistance factors for these compounds were 184, 1547, 5971 and 35, respectively. A 23.5-fold increase in 7-ethoxy-4-trifluoromethylcoumarin O-deethylation activity suggested that metabolic resistance through elevated levels of cytochrome P450 dependent monooxygenase-activity is a possible resistance mechanism.

However, synergism studies with different metabolic inhibitors revealed some contrasting resistance mechanisms between the METI-acaricides. Tebufenpyrad resistance could only be synergized after pre-treatment with the monooxygenase inhibitor piperonyl butoxide (PBO), whereas pyridaben resistance was strongly synergized both by PBO and the esterase inhibitor S,S,S-tributylphosphorotrithioate (DEF). Resistance levels to fenpyroximate could neither be suppressed by PBO nor by DEF. Although METI-acaricides are structurally related, these findings probably reflect a different role of esterases and mono-oxygenases in metabolic detoxification between these compounds. The overall lack of synergism by diethylmaleate (DEM) suggests that glutathione-S-transferases are not an important factor in resistance to METIs.

Reciprocal crosses between susceptible females and resistant males showed no maternal effect, and resistance to METI-acaricides was inherited generally as a dominant trait. Backcrosses with F1 females revealed striking differences in the mode of inheritance. Although resistance to fenpyroximate and pyridaben was under monogenic control, resistance to tebufenpyrad was under control of more than one gene.

The effect of delayed mating on reproductive potential, longevity and oviposition period of female redbanded leafroller, Argyrotaenia velutinana (Walker) and Pandemis leafroller, Pandemis pyrusana Kearfott, was investigated in the laboratory. Virgin female or male moths of each species were held for 1, 2, 4, 6 or 10 days prior to pairing with one-day-old virgin conspecifics of the opposite sex. In addition, reproductive potential was assessed when both sexes of each species were aged for those periods prior to pairing. The expected reproduction of female A. velutinana was reduced by 34, 53, 71 and 81% for 2, 4, 6 and 10-day delays in female mating, respectively. For P. pyrusana, expected reproduction was reduced by 47, 74, 85 and 93% for 2, 4, 6 and 10-day delays in female mating, respectively. Increasing male age at mating in both species had a lesser effect on female reproductive output compared with increasing female age at mating. As male A. velutinana age at mating increased, the expected reproduction of female A. velutinana was reduced by 15, 45, 54 and 70% for 2, 4, 6 and 10-day delays, respectively. Comparing male P. pyrusana of various ages at mating, expected reproduction was reduced by 14, 42, 64 and 79% for 2, 4, 6 and 10-day delays in mating, respectively. The decrease in female reproduction when both sexes were aged prior to mating was higher than when either sex alone was aged prior to pairing with a one-day-old virgin of the opposite sex. The expected reproduction of female A. velutinana was reduced by 60, 83, 96 and 98% for 2, 4, 6 and 10-day delays in mating of both sexes, respectively. Only 7.5% of female eggs hatched when both sexes of A. velutinana were aged ten days prior to mating. When simultaneously aging both sexes of P. pyrusana prior to mating, expected reproduction was reduced by 71, 93, 96 and 99% for 2, 4, 6 and 10-day delays in mating, respectively. No P. pyrusana eggs hatched after a ten-day delay of mating for both sexes. For both species, female longevity increased and duration of oviposition period decreased with increasing female age at mating. Our results demonstrate that delayed mating in both females and males negatively affects female reproductive output in both species and that simultaneous aging of both sexes prior to mating has a greater effect than aging either sex alone. Our results suggest that laboratory studies that have paired aged females or aged males with conspecifics of optimal reproductive maturity have likely underestimated the effects of delayed mating on reproductive output.

Predators are important determinants of the spatiotemporal distribution of prey within a given habitat. The predator effects may vary with diet specialisation, the associated risk posed to prey and, if multiple predators are present, the predator-predator interactions. We examined the spatiotemporal distribution of the herbivorous spider mite Tetranychus urticae and the associated specialist and generalist predators Phytoseiulus persimilis and Neoseiulus californicus on bean plants. Tetranychus urticae is a key pest on numerous agricultural crops. Both predators are used singly and in combination for biological control of spider mites. Population development and within-plant distribution of the spider mites and the predators were compared among five treatments: T. urticae without predators, with either predator alone and with both predators in combination at full and half densities. The spider mites were suppressed to zero density in both predator combination treatments but not in the single predator treatments. The predators determined the spatiotemporal distribution of the spider mites through density- and behaviour-mediated effects, and these effects were linked to diet specialisation. The specialist P. persimilis exerted stronger density-mediated effects on the spider mite distribution than did the generalist N. californicus. Either predator induced in the spider mites early upward migration on plants. The predators also affected each other's distribution. The aggregation level of N. californicus was lowered by P. persimilis but not vice versa. In combination, the predators were more dispersed than when alone, reducing the predator-free space and leading to the local extinction of T. urticae.

Two Napier millet (Pennisetum purpureum×P. glaucum) hybrids, namely PBN 83 and PBN 233 and one sorghum (Sorghum bicolor) variety, SL 44, were assessed for their potential role as a trap crop in the management of the stem borer, Chilo partellus (Swinhoe) (Lepidoptera: Crambidae) on maize. Oviposition preference and larval survival and development were determined for different test plants under laboratory and screen house conditions. Further, field dispersal of C. partellus larvae was assessed between Napier millet and maize crops. Results from no-choice and dual-choice tests indicated that Napier millet hybrids were preferred for oviposition over maize by C. partellus moths. Sorghum was, however, not preferred over maize in this respect. Napier millet hybrids were poor larval hosts, and a rapid decline in larval numbers was noticed within the first five days after hatching and virtually no larvae survived to pupation. Leaf area eaten by the borer larvae was significantly less on these hybrids than on maize or sorghum. Plant damage was more severe in maize and sorghum than Napier millet hybrids. No appreciable larval shift was noticed from Napier millet hybrids to the adjoining maize crop. The evaluated Napier millet hybrids, therefore, had potential for use as trap crop in C. partellus management. Sorghum, however, did not hold promise in this respect.

Alighting of horse flies (Diptera: Tabanidae) and non-biting muscids (Diptera: Muscidae) was studied at Khartoum, Sudan, using black cylindrical models mimicking a goat, calf and cow. Flies were intercepted by attaching electrocution grids or clear adhesive film to models. Alighting sites and defensive behaviour were also documented on hosts through observation. Female Tabanus sufis (Jennicke), T. taeniola (Palisot) and Atylotus agrestis (Wiedemann) were the main tabanids captured. Muscids landed in equal numbers on all sizes of models. They had a strong preference for the upper portions of both models and hosts. Landings of T. taeniola and A. agrestis increased with model size, but not so for T. sufis. T. taeniola and A. agrestis scarcely alighted on the legs of models whereas 60–78% of T. sufis did so. Landings of T. sufis on artificial legs did not vary with model size. Landings of all tabanids on the lower and upper portions of a model increased with model size. For both hosts and models, most tabanids (88–98%) alighted on the lower half and legs. Most muscids (63–89%) alighted on the upper half. Landing of tabanids on the cow was 34.9 and 69.3 times greater than that on the calf and goat, respectively. These results are discussed in relation to strategies for the control of blood-sucking flies associated with farm animals using either insecticide-treated live baits or their mimics.

The activity of detoxifying enzymes (glutathione-S-transferases (GST), mixed-function oxidases (MFO), and esterases (EST)) and the presence of insensitive variants of target proteins (sodium channel and acetylcholinesterase) were examined in individual male and female codling moths. Twenty-nine populations from 11 countries and two laboratory strains were examined. Populations were classified as either unsprayed or sprayed. The ranges of enzyme activities across field populations varied 15-fold, 485-fold and fourfold for GST, MFO and EST, respectively. MFO was the only enzyme whose activity differed in a binomial classification of orchards based on their spray history. Few differences in enzyme activities were found due to sex among populations; and, in these cases, males had higher GST and lower MFO and EST activities than females. Activities of the three enzymatic systems across all populations were positively correlated. Populations from Greece, Argentina and Uruguay had significant percentages of moths with elevated GST and MFO activities. The co-occurrence of moths expressing both elevated MFO and low EST activities was found in conventional orchards from the Czech Republic and France. Chile was the only country where populations from treated orchards did not include a significant proportion of individuals with enhanced enzyme activity. The kdr mutation was found at significant levels in ten populations from five countries, including all French and Argentinean populations. The mutation in AChE was only detected in the Spanish population.

Morphologically, early immature stages of the economically important pest called screwworms, Cochliomyia hominivorax (Coquerel) (Diptera: Calliphoridae), and non-pest secondary screwworms, Cochliomyia macellaria (Fabricius) (Diptera: Calliphoridae), are nearly indistinguishable. Correct identification is crucial to the ongoing eradication and exclusion program protecting the United States, Mexico and Central America from reinvasion of screwworms persistent in South America and the Caribbean. Amplified fragment length polymorphism (AFLP) polymerase chain reaction was used to differentiate populations of C. hominivorax and to discriminate them from C. macellaria. Ten primer pairs screened for interspecific discrimination of C. hominivorax from C. macellaria showed 52 discrete bands, allowing the two species to be readily distinguished; divergent branches on resulting dendrograms showed 100% bootstrap support. C. macellaria populations grouped at the 92% level; C. hominivorax populations grouped at the 68% level. Of the 52 bands, seven were monomorphic for both species, 22 were specific to C. macellaria, ten were present only in C. hominivorax and the remaining 13 bands differentiated C. hominivorax populations. Separate studies using ten strains of C. hominivorax showed a higher level of genetic similarity within than between populations. Analyses using 72 bands (19 monomorphic bands, 53 bands grouped all ten strains at the 58% similarity level) resolved seven mutant strains from Mexico (85% similarity level); all ten strains were resolved at the 72% similarity level. Diagnostic bands were identified for species and strain identification. We conclude that AFLP can be a valuable tool for studies of interspecific and intraspecific genetic variation in screwworm populations.