Macroecology of local insect communities

The inter-relationships between animal body weight, range size, species richness and abundance are currently the basis of macroecology. Using 41 099 insects sampled from 31 Acacia tree canopies in north-east Tanzania, we first documented the basic macroecological patterns. The relationship between body weight and both species richness and abundance was polygonal with the highest insect species richness and abundance occurring at intermediate body weights. Across individual tree communities, the most statistically robust relationships were found between range size, abundance and species richness and they were all linear. In a second part, we focused on the positive abundance-range size relationship and we could test predictions of six of the eight proposed hypotheses to explain this widely documented pattern of community structure. The relationship is most likely explained by the metapopulation hypothesis stating that with more patches being occupied, local abundance in a given patch increases due to a higher rate of immigration from nearby patches. In addition, we found high slopes for the species-area relationship, typical of island systems and thus it seems reasonable to characterise Acacia trees in the savannah as habitat islands for insects.     

The importance of relative humidity and trophic resources in governing ecological niche of the invasive carabid beetle Merizodus soledadinus in the Kerguelen archipelago

Comprehensive studies to identify species-specific drivers of survival to environmental stress, reproduction, growth, and recruitment are vital to gaining a better understanding of the main ecological factors shaping species habitat distribution and dispersal routes. The present study performed a field-based assessment of habitat distribution in the invasive carabid beetle Merizodus soledadinus for the Kerguelen archipelago. The results emphasised humid habitats as a key element of the insect’s realised niche. In addition, insects faced food and water stress during dispersal events. We evaluated quantitatively how water availability and trophic resources governed the spatial distribution of this invasive predatory insect at Îles Kerguelen. Food and water stress survival durations [in 100%, 70%, and 30% relative humidity (RH) conditions] and changes in a set of primary metabolic compounds (metabolomics) were determined. Adult M. soledadinus supplied with water ad libitum were highly tolerant to prolonged starvation (LT₅₀ = 51.7 ± 6.2 d). However, food-deprived insect survival decreased rapidly in moderate (70% RH, LT₅₀ = 30.37 ± 1.39 h) and low (30% RH, LT₅₀ = 13.03 ± 0.48 h) RH conditions. Consistently, body water content decreased rapidly in insects exposed to 70% and 30% RH. Metabolic variation evidenced the effects of food deprivation in control insects (exposed to 100% RH), which exhibited a progressive decline of most glycolytic sugars and tricarboxylic acid cycle intermediates. Most metabolite levels were elevated levels during the first few hours of exposure to 30% and 70% RH. Augmented alanine and lactate levels suggested a shift to anaerobic metabolism. Simultaneously, peaks in threonine and glycolytic sugars pointed to metabolic disruption and a progressive physiological breakdown in dehydrating individuals. Overall, the results of our study indicate that the geographic distribution of M. soledadinus populations is highly dependent on habitat RH and water accessibility.     

Impacts of antemortem ingestion of alcoholic beverages on insect successional patterns

This paper studies the impacts of antemortem ingestion of alcoholic beverages by the domestic rabbit, Oryctolagus cuniculus L., on postmortem successional patterns of insects during winter and summer 2018 in Riyadh, Saudi Arabia. Insect samples were collected from the carcasses of rabbits fed alcoholic beverages as well as untreated rabbits for 15 days postmortem during two successional studies in each season. The results showed that, during both seasons, the decomposition process for the carcasses of rabbits fed alcoholic beverages antemortem was one to two days longer. The results also showed, however, that alcoholic beverages did not affect insect succession patterns in either season. In fact, the number of insects appeared to be influenced by the ambient temperature during the two seasons, with 4415 insects in the winter compared to 1033 insects in the summer. In total, 30 insect taxa were collected during the winter study from the carcasses of rabbits fed alcoholic beverages antemortem; while 26 of these same taxa were collected from the carcasses of the untreated rabbits. Among the treated rabbits, those fed 25 ml alcoholic beverages treated attracted the highest number of insect taxa (24 taxa). In the summer study, 21 insect taxa were collected in total, 19 from the carcasses of the alcohol-treated rabbits and 13 from untreated rabbits. Among the treated rabbits, those fed 50 ml alcoholic beverages attracted the highest number of insect taxa (14 taxa). These results contribute to the understanding of the factors affecting the use of insects in medical investigations, given that alcoholic beverages are a common addictive agent.     

Effect of dimethoate on the developmental rate of forensic importance Calliphoridae flies

Forensic entomotoxicology has grown to impact judicial systems in developed countries. Where the use of insects and maggots as samples in death investigations as an alternative technique, especially following degradation or loss of the conventionally used samples. Carrion flies feed on dead bodies and may ingest toxic substances found in the dead body, especially when the body was poisoned before death. The knowledge of how the chemicals interact with the insect following ingestion is crucial to forensic entomotoxicologists. The study investigated the impact of dimethoate on the life cycle of four species of Calliphoridae flies, namely Chrysomya megacephala, Chrysomya saffranea, Chrysomya rufifacies and Chrysomya indiana. Various concentrations of dimethoate (1 ppm, 2 ppm, 3 ppm and 4 ppm) were utilized in the study. The rate of development of the carrion flies showed a negative correlation with the concentration of the chemical. This paper glares at the impact of the chemicals may pose to the insects, and how analysis of such impacts can guide forensic investigations of poisoning and help the investigators to solve the crime puzzle.     

Patch size has no effect on insect visitation rate per unit area in garden-scale flower patches

Previous studies investigating the effect of flower patch size on insect flower visitation rate have compared relatively large patches (10–1000s m²) and have generally found a negative relationship per unit area or per flower. Here, we investigate the effects of patch size on insect visitation in patches of smaller area (range c. 0.1–3.1 m²), which are of particular relevance to ornamental flower beds in parks and gardens. We studied two common garden plant species in full bloom with 6 patch sizes each: borage (Borago officinalis) and lavender (Lavandula × intermedia ‘Grosso’). We quantified flower visitation by insects by making repeated counts of the insects foraging at each patch. On borage, all insects were honey bees (Apis mellifera, n = 5506 counts). On lavender, insects (n = 737 counts) were bumble bees (Bombus spp., 76.9%), flies (Diptera, 22.4%), and butterflies (Lepidoptera, 0.7%). On both plant species we found positive linear effects of patch size on insect numbers. However, there was no effect of patch size on the number of insects per unit area or per flower and, on lavender, for all insects combined or only bumble bees. The results show that it is possible to make unbiased comparisons of the attractiveness of plant species or varieties to flower-visiting insects using patches of different size within the small scale range studied and make possible projects aimed at comparing ornamental plant varieties using existing garden flower patches of variable area.     

Infection and colonization of tissues of the aphid Myzus persicae and cassava mealybug Phenacoccus manihoti by the fungus Beauveria bassiana

Histopathogenesis of living insects of Myzus persicae Sulzer (Hemiptera: Aphididae) and Phenacoccus manihoti Matile‐Ferrero (Hemiptera: Pseudococcidae) by Beauveria bassiana (Balsamo) Vuillemin (Ascomycota: Hypocreales) was monitored from penetration through insect death. Important events in aphids included fungal penetration of the integument of the less-resistant leg intersegmental membrane and invasion of natural openings, formation of hyphal bodies in live aphids by three days post-inoculation (PI), and extensive hyphal colonization of the two leg segments closest to the insect body at death of the aphids. Confocal microscopy of green fluorescent protein-labeled B. bassiana in live mealybugs indicated the fungus penetrated the host through the legs and mouthparts. The fungus was scarce in live mealybugs at 1–5 days PI, formed hyphal bodies by six days PI, and growth was limited to parts of dead hosts at 6–7 days PI. In dead mealybugs, hyphal bodies were near solid tissue. Blastospores were in the hemolymph.     

Biostable insect kinin analogs reduce blood meal and disrupt ecdysis in the blood-gorging Chagas’ disease vector,Rhodnius prolixus

Rhodnius prolixus is a blood-gorging hemipteran that takes blood meals that are approximately 10 times its body weight. This blood meal is crucial for growth and development and is needed to ensure a successful molt into the next instar. Kinins are a multifunctional family of neuropeptides which have been shown to play a role in the control of feeding in a variety of insects. In this study, two biostable Aib-containing kinin analogs were tested to see if they interfere with blood-feeding and subsequent development into the next instar. One of the analogs, 1729 (Ac-R[Aib]FF[Aib]WGa), had no effect on the size of the blood meal or on the subsequent molting of the insect into the next instar. This analog also did not interfere with either short-term or long-term diuresis. The second analog, 1728 ([Aib]FF[Aib]WGa), appeared to be an antifeedant. Insects feeding on blood containing this analog (15 μM) only consumed 60% of the blood meal taken by insects fed on blood without analog. Insects feeding on blood containing 1728 had a slower rate of rapid diuresis (diuresis in the first 3–5 h after feeding) leading to less urine being excreted by 5 days post feeding. The consequence of these effects was that insects fed on 1728 did not molt. This data indicates that the biostable Aib-containing analog 1728 disrupts normal growth and development in the blood-feeding insect, R. prolixus.     

Ovarian and fat body protein concentrations in Ips sexdentatus (Coleoptera: Scolytidae) parasitized by nematodes

The protein concentrations of fat body and ovaries in Ips sexdentatus either uninfected or infected by Parasitaphelenchus sp., P. sexdentati, or Contortylenchus diplogaster were measured at various stages of insect development, from preswarming maturation to the first oviposition (24 hr after mating). Weight variations of the fat body and ovaries in insects infected by C. diplogaster show the same evolution as those observed in uninfected insects, but at a much lower level. Fat body proteins in uninfected insects reach their minimum level during swarming, but they remain fairly constant throughout the maturation of the first egg. After dropping shortly after swarming, the ovarian protein level in such insects increases in two stages during ovarian maturation. The first stage, which corresponds to a slow protein incorporation, takes place during the first 12 hr after mating. During the second stage, i.e., beyond 12 hr, a significant level of proteins is rapidly incorporated into the ovaries. In insects infected by Parasitaphelenchus fat body proteins are reduced and protein incorporation into the ovaries is reduced; Parasitaphelenchus would thus affect at least some proteins required for ovarian maturation in their host. Fat body protein levels are even more affected by C. diplogaster than by Parasitaphelenchus, while incorporation into ovaries seems to be less affected in spite of slower ovarian growth. C. diplogaster might thus essentially act both upon proteins which are not required for the ovarian maturation of their host and upon nonproteinaceous substances that are required for such maturation. Results are discussed in relation to the possible mode of action of parasitic nematodes.     

Effects of native pollinator communities on the physiological and chemical parameters of loquat tree (Eriobotrya japonica) under open field condition

Wild and managed pollinators are the key component of biodiversity, contributing to important ecosystem services such as pollination and supporting human food security. Pollination by insects is a crucial component of the food chain that ensures the production of fruits and strongly affects the fruit quality, but the effect of insect pollination on fruit physiological and chemical parameters is largely unknown. The current study was conducted to determine the insect pollinators diversity and their relative abundance in the loquat (Eriobotrya japonica) orchard during 2017–2019. Further, the effect of insect pollinators pollination on the physiological and chemical parameters of fruit quality as compared to control pollinated flowers was investigated. The results revealed that a total of 22 species from 3 families (Apidae, Halictidae, and Syrphidae) were identified during the flowering season. The Apidae and Syrphidae were the most frequently observed families with major groups honey bees (67.89%) and hoverflies (21.57%), respectively. Moreover, results indicated that the fruit yield by the open-pollinated flowers (22.31 ± 0.34 kg/tree) was significantly higher than the control pollinated flowers (14.80 ± 0.25 kg/tree). Physiological and chemical parameters of loquat fruit differed significantly when fruits obtained from open-pollinated flowers as compared to control pollinated flowers. These results suggested that native insect pollinators play important role in the fruit quality of loquat. Hence, maintenance of appropriate habitat of native pollinators near loquat orchards is necessary to ensure good productivity and fruit quality.     

Physiological factors for tolerance of <Emphasis Type="Italic">Kosteletzkya virginica</Emphasis> (L.) Presl to one-instar bollworms of <Emphasis Type="Italic">Helicoverpa armigera</Emphasis> (Hubner)

An experiment was designed to investigate the tolerance and response of the Kosteletzkya virginica (L.) Presl to one-instar bollworms of Helicoverpa armigera (Hubner). In this experiment, the insects obviously brought an enhancement in damaged rate of leaf area (DRLA), average diameter of bitten hole (ADBH) and average grade of leaf damage (AGLD) in K. virginica seedlings. When amount of insect increased to 4 per top leaf, the average DRLA, AABH, ADBH and AGLD were 8.6%, 9.2 mm, 2.7 mm and 2.0 mm, respectively, and the seedlings showed a potential insect-tolerance to this insect stress. Furthermore, with an increase of insect density, MDA, relative permeability of membrane (RPM), O₂^−· production and soluble sugar concentration all enhanced, whereas activities of SOD and POD increased and subsequently declined. By statistical analysis, it was drawn that bio-toxicity of O₂^−· was the first destroying factor, cell membrane decomposition ranked the second, and the destruction of membrane lipid peroxidation was the slightest to K. virginica seedlings. Moreover, under the insect stress, POD was the most significant factor in protecting the seedlings, soluble sugar acted as the subordinate one, and the protection of SOD was the slightest compared to two others. In addition, insect stress obviously affected chlorophyll-fluorescence characteristics, and resulted in a significant increase in Fo and qN, and a significant reduction in Fv/Fm, ETR and qP during experiment.     

Effects of spawning Pacific salmon on terrestrial invertebrates: Insects near spawning habitat are isotopically enriched with nitrogen‐15 but display no differences in body size

When Pacific salmon (Oncorhynchus spp.) spawn and die, they deliver marine‐derived nutrient subsidies to freshwater and riparian ecosystems. These subsidies can alter the behavior, productivity, and abundance of recipient species and their habitats. Isotopes, such as nitrogen‐15 (¹⁵N), are often used to trace the destination of marine‐derived nutrients in riparian habitats. However, few studies have tested for correlations between stable isotopes and physiological responses of riparian organisms. We examined whether increases in δ ¹⁵N in terrestrial insect bodies adjacent to salmon spawning habitat translate to changes in percent nitrogen content and body size. This involved comparisons between distance from a salmon‐bearing river, marine‐derived nutrients in soils and insects, soil moisture content, and body size and nitrogen content in two common beetle families (Coleoptera: Curculionidae, Carabidae). As predicted, δ¹⁵N in riparian soils attenuated with distance from the river but was unaffected by soil moisture. This gradient was mirrored by δ¹⁵N in the herbivorous curculionid beetles, whereas carabid beetles, which feed at a higher trophic level and are more mobile, did not show discernable patterns in their δ¹⁵N content. Additionally, neither distance from the river nor body δ¹⁵N content was related to beetle body size. We also found that nitrogen‐15 was not correlated with total percent nitrogen in insect bodies, meaning that the presence of spawning salmon did not increase the percent nitrogen content of these insects. We conclude that while salmon‐derived nutrients had entered terrestrial food webs, the presence of δ¹⁵N alone did not indicate meaningful physiological changes in these insects in terms of percent nitrogen nor body size. While stable isotopes may be useful tracers of marine‐derived nutrients, they cannot necessarily be used as a proxy for physiologically important response variables.     

Influence of insects and fungal pathogens on individual and population parameters of <Emphasis Type="Italic">Cirsium arvense</Emphasis> in its native and introduced ranges

Introduced weeds are hypothesized to be invasive in their exotic ranges due to release from natural enemies. Cirsium arvense (Californian, Canada, or creeping thistle) is a weed of Eurasian origin that was inadvertently introduced to New Zealand (NZ), where it is presently one of the worst invasive weeds. We tested the ‘enemy release hypothesis’ (ERH) by establishing natural enemy exclusion plots in both the native (Europe) and introduced (NZ) ranges of C. arvense. We followed the development and fate of individually labelled shoots and recorded recruitment of new shoots into the population over two years. Natural enemy exclusion had minimal impact on shoot height and relative growth rate in either range. However, natural enemies did have a significant effect on shoot population growth and development in the native range, supporting the ERH. In year one, exclusion of insect herbivores increased mean population growth by 2.1–3.6 shoots m⁻², and in year two exclusion of pathogens increased mean population growth by 2.7–4.1 shoots m⁻². Exclusion of insect herbivores in the native range also increased the probability of shoots developing from the budding to the reproductive growth stage by 4.0× in the first year, and 13.4× in the second year; but exclusion of pathogens had no effect on shoot development in either year. In accordance with the ERH, exclusion of insect herbivores and pathogens did not benefit shoot development or population growth in the introduced range. In either range, we found no evidence for an additive benefit of dual exclusion of insects and pathogens, and in no case was there an interaction between insect and pathogen exclusion. This study further demonstrates the value of conducting manipulative experiments in the native and introduced ranges of an invasive plant to elucidate invasion mechanisms.     

Occurrence and characterization of injuries caused by Mycotretus apicalis Lacordaire, 1842 (Coleoptera: Erotylidae) on cultivation of Pleurotus sajor-caju

When carrying out experiments on the production of the edible mushroom Pleurotus sajor-caju in the Laboratory of Edible Mushrooms, Universidade Federal de Lavras, Lavras, Brazil, in the second half of 2007, the presence of beetles later identified as belonging to the species Mycotretus apicalis was verified. This is the first recorded instance of this insect in cultures of P. sajor-caju in Brazil. The larvae and adults of this insect feed on the fruiting bodies of commercial harvests, resulting in reduction in mushroom quality. To provide evaluation of the injuries caused by these insects, substrates colonized by P. sajor-caju were infested with 4, 8, 16, 32 and 64 insects per block of substrate being the qualitative and quantitative losses then noted. Despite the lack of an observed decrease in biological efficiency, the injuries caused by these insects affected the commercial quality of the mushrooms, which may result in economic losses. The results showed that infestations of 32 insects per 0.8 kg of substrate led to a depreciation in the prices of mushrooms meant to be sold.     

Volatile compounds from Liposcelis bostrychophila (Psocoptera: Liposcelididae) and their environment and their effects on settling behaviour

Headspace from above either Liposcelis bostrychophila Badonnel reared on powdered food; insects without food or from powdered food only were collected on five occasions over a period of four weeks. Volatiles were analysed by thermal desorption gas chromatography-mass spectrometry (TD-GCMS) to look for ecologically significant volatile compounds. Hexanoic acid (HA) was the major compound in the insect only and diet only volatiles (insect 25.6 ± 1.6%, diet 32.9 ± 1.13%). Isobutyric acid was the main compound detected in the volatiles from both insects and diet (35.3 ± 6%). Butyric acid (BA) and acetoin (HB) were also present at >2% of the total peak areas. HB was not detected in the insect only volatiles. Bioassays showed that hexanoic acid was the most repellent chemical. Mixtures of compounds representing the proportions of HA, BA, IBA, and HB in the volatiles did not have any prolonged effect on settling or selection by booklice in a two choice bioassay. L. bostrychophila can avoid individual volatile chemicals but the effects can be masked when they are incorporated into mixtures. As some volatile compounds can be detected by booklice they may govern dispersal, but further work is required to clarify their significance.     

Mechanisms of dsRNA uptake in insects and potential of RNAi for pest control: A review

RNA interference already proved its usefulness in functional genomic research on insects, but it also has considerable potential for the control of pest insects. For this purpose, the insect should be able to autonomously take up the dsRNA, for example through feeding and digestion in its midgut. In this review we bring together current knowledge on the uptake mechanisms of dsRNA in insects and the potential of RNAi to affect pest insects. At least two pathways for dsRNA uptake in insects are described: the transmembrane channel-mediated uptake mechanism based on Caenorhabditis elegans’ SID-1 protein and an ‘alternative’ endocytosis-mediated uptake mechanism. In the second part of the review dsRNA feeding experiments on insects are brought together for the first time, highlighting the achievement of implementing RNAi in insect control with the first successful experiments in transgenic plants and the diversity of successfully tested insect orders/species and target genes. We conclude with points of discussion and concerns regarding further research on dsRNA uptake mechanisms and the promising application possibilities for RNAi in insect control.     

The trehalose transporter 1 gene sequence is conserved in insects and encodes proteins with different kinetic properties involved in trehalose import into peripheral tissues

We recently cloned a trehalose transporter gene (Tret1) that contributes to anhydrobiosis induction in the sleeping chironomid Polypedilum vanderplanki Hinton. Because trehalose is the main haemolymph sugar in most insects, they might possess Tret1 orthologs involved in maintaining haemolymph trehalose levels. We cloned Tret1 orthologs from four species in three insect orders. The similarities of the amino acid sequence to TRET1 in P. vanderplanki were 58.5–80.4%. Phylogenetic analysis suggested the Tret1 sequences were conserved in insects. The Xenopus oocyte expression system showed apparent differences in the K_m and V_max values for trehalose transport activity among the six proteins encoded by the corresponding orthologs. The TRET1 orthologs of Anopheles gambiae (K_m: 45.74 ± 3.58 mM) and Bombyx mori (71.58 ± 6.45 mM) showed low trehalose affinity, whereas those of Apis mellifera (9.42 ± 2.37 mM) and Drosophila melanogaster (10.94 ± 7.70 mM) showed high affinity. This difference in kinetics might be reflected in the haemolymph trehalose:glucose ratio of each species. Tret1 was expressed not only in the fat body but also in muscle and testis. These findings suggest that insect TRET1 is responsible for the release of trehalose from the fat body and the incorporation of trehalose into other tissues that require a carbon source, thereby regulating trehalose levels in the haemolymph.     

The value of insect pollination to yield of oilseed rape (Brassica rapa) in Bangladesh

Brassica rapa L., is a crop grown globally and studies have indicated that insect pollination can improve yields. However, the importance of insect pollination in this crop depends on cultivar reproductive biology, insect pollinator species and their abundances. In Bangladesh, the acreage of B. rapa for oilseed production has been expanding, but little is known about whether insects contribute to yield improvements. Using the commonly grown variety Tori-7, we found that plants with inflorescences left exposed to flower visiting insects (body width > 1.5 mm) had a 30.8% greater seed yield compared to those where insect flower visitors were excluded. Of 794 insect flower visiting individuals recorded from observation and trapping surveys conducted across four separate fields, Apis bees (four spp.) were the most abundant (66.1%), followed by flies Musca domestica (14.7%), Sepsis fulgens (6.3%) and hoverflies (3.0%; 3 spp; Syrphidae). Other flower visitors included ants, wasps, beetles, butterflies and moths. For the cultivar assessed, we calculated the economic value of oilseed rape was $US 87.5 million per annum in Bangladesh, of which the economic value of insect pollination was $US 26.92 million per annum. Thus, one in every four dollars earned by our Bangladeshi growers resulted from insect crop pollination. This demonstrates to growers the need to promote and protect insect pollination to optimize their economic returns.     

Leaf litter quality affects aquatic insect emergence: contrasting patterns from two foundation trees

Reciprocal subsidies between rivers and terrestrial habitats are common where terrestrial leaf litter provides energy to aquatic invertebrates while emerging aquatic insects provide energy to terrestrial predators (e.g., birds, lizards, spiders). We examined how aquatic insect emergence changed seasonally with litter from two foundation riparian trees, whose litter often dominates riparian streams of the southwestern United States: Fremont (Populus fremontii) and narrowleaf (Populus angustifolia) cottonwood. P. fremontii litter is fast-decomposing and lower in defensive phytochemicals (i.e., condensed tannins, lignin) relative to P. angustifolia. We experimentally manipulated leaf litter from these two species by placing them in leaf enclosures with emergence traps attached in order to determine how leaf type influenced insect emergence. Contrary to our initial predictions, we found that packs with slow-decomposing leaves tended to support more emergent insects relative to packs with fast-decomposing leaves. Three findings emerged. Firstly, abundance (number of emerging insects m^?2 day^?1) was 25 % higher on narrowleaf compared to Fremont leaves for the spring but did not differ in the fall, demonstrating that leaf quality from two dominant trees of the same genus yielded different emergence patterns and that these patterns changed seasonally. Secondly, functional feeding groups of emerging insects differed between treatments and seasons. Specifically, in the spring collector-gatherer abundance and biomass were higher on narrowleaf leaves, whereas collector-filterer abundance and biomass were higher on Fremont leaves. Shredder abundance and biomass were higher on narrowleaf leaves in the fall. Thirdly, diversity (Shannon’s H′) was higher on Fremont leaves in the spring, but no differences were found in the fall, showing that fast-decomposing leaves can support a more diverse, complex emergent insect assemblage during certain times of the year. Collectively, these results challenge the notion that leaf quality is a simple function of decomposition, suggesting instead that aquatic insects benefit differentially from different leaf types, such that some use slow-decomposing litter for habitat and its temporal longevity and others utilize fast-decomposing litter with more immediate nutrient release.     

Insect biodiversity meets ecosystem function: differential effects of habitat and insects on carrion decomposition

1. Ecological processes are maintained in different environments by different species performing similar functional roles. Yet, little is known about the role of the environment in shaping insect biodiversity associated with a process that is ephemeral and patchy. 2. In this study, the mass loss of carrion in response to contrasting habitat types (grassland or tree) was quantified experimentally, as well as the presence, diversity and composition of insect assemblages. Differences in insect assemblages between these two habitats were also examined. 3. It was found that the presence of insects led to a doubling in mass loss, but that grassland or tree habitat type had no effect on this process. By contrast, habitat type had a significant effect on the composition of generalist ant and beetle assemblages, but not on specialist fly assemblages. Given the colonisation of insects, carrion mass loss was negatively associated with increasing evenness of fly assemblages and increasing ant abundance. Variation in fly assemblage composition was also found to correlate with variation in carrion mass loss. 4. This study highlights the major role of habitat type in shaping the composition of generalist insects at carrion, but the minor role in affecting specialist and highly vagile insects. This complements the authors' findings that insect colonisation of carrion was critical to accelerated mass loss, and that fly assemblages were responsible for variation in this process, regardless of habitat. The present study sheds new light on the contribution of insect biodiversity to decomposition in variable environments, with consequences for carrion food webs and nutrient cycling.