Effects of Season and Vegetation Type on Community Organization of Dung Beetles in a Tropical Dry Forest1

Dung beetles are important components of most terrestrial ecosystems. In tropical rain forests, dung beetle communities can be very rich in number of species and individuals, and they are known to be useful bioindicators of habitat disturbance. In contrast, very little is known about the organization of dung beetle communities in tropical dry forests. The aim of this study was to describe in detail the dung beetle community of a Mexican tropical dry forest and to assess the relative importance of rainfall seasonality and forest structure in affecting the temporal and spatial dynamics of this community. Dung beetles were captured with pitfall traps at the beginning of the rainy season, the middle of the rainy season, and the middle of the dry season, in two distinct forest types: deciduous forest (DF) and semideciduous forest (SDF) at the Estación de Biología Chamela. Both rainfall seasonality and forest structure affected the community organization of dung beetles. During both rainy periods, 14 species were captured, but only three during the dry season. Dung beetles captured during the dry season were only found in the SDF. When comparing the beginning and the middle of the rainy season, differences in abundance and guild structure were also observed between both periods and between forest types, but these differences were much less pronounced.     

Rain forest provides pollinating beetles for atemoya crops

Small beetles, usually species of Nitidulidae, are the natural pollinators of atemoya (Annona squamosa L. x A. cherimola Mill. hybrids; custard apple) flowers but commercial atemoya growers often need to carry out labor-intensive hand pollination to produce enough high-quality fruit. Because Australian rain forest has plant species in the same family as atemoya (Annonaceae) and because many rain forest plants are beetle pollinated, we set out to discover whether tropical rain forest in far north Queensland harbors beetles that could provide this ecosystem service for atemoya crops. Orchards were chosen along a gradient of increasing distance from tropical rain forest (0.1-24 km). We sampled 100 flowers from each of nine atemoya orchards and determined the identity and abundance of insects within each flower. To assess the amount of pollination due to insects, we bagged six flowers per tree and left another six flowers per tree accessible to insects on 10 trees at an orchard near rain forest. Results indicated that atemoya orchards < or = 0.5 km from rain forest were predominantly visited by five previously unrecognized native beetle pollinators that are likely to originate in tropical rain forest. These native beetles occurred reliably enough in crops near rain forest to have a positive effect on the quantity of fruit produced but their contribution was not great enough to satisfy commercial production needs. Management changes, aimed at increasing native beetle abundance in crops, are required before these beetles could eliminate the need for growers to hand pollinate atemoya flowers. Appreciation of the value of this resource is necessary if we are to develop landscapes that both conserve native biodiversity and support agricultural production.     

How much have we learned about seasonality in tropical insect abundance since Wolda (1988)?

Seasonal patterns in climatic conditions affect the life cycles and temporal patterns in the abundance of most temperate insect species. In tropical regions where there is no winter season, the situation may be different. For a better understanding of the evolution of seasonal life cycles, and the dynamics affecting temporal patterns in abundance of tropical insect populations and assemblages, it is important to study the life cycles of tropical insects and the presence or absence of seasonality in relation to climatic conditions. By reviewing studies on temporal patterns of abundance, this article examines the patterns of seasonality in adult tropical forest insects and discusses the variation in such patterns in various forest types. Seasonal and aseasonal patterns were found to be common in tropical dry and wet regions, respectively. In wet regions, which lack a distinctive dry season, there exists a wide variety of temporal patterns in addition to aseasonal patterns: distinctively seasonal and supra‐annual fluctuations in some insect species. Some of the problems of hidden ecological mechanisms underlying seasonal patterns in abundance are discussed, and the definition of seasonality in temporal patterns of insect abundance at a particular stage in the life cycle is considered. Methodological problems are also discussed.     

Population persistence of the parasitoid fly Zaira cinerea (Fallén) (Diptera: Tachinidae) utilizing multiple host carabid beetles with different seasonality and quality

Zaira cinerea (Fallén) is a parasitoid fly (Diptera: Tachinidae) that attacks adult carabid beetles. To better understand mechanisms of population persistence in this species, we examined seasonality of host beetle abundance, the frequency of parasitism, and the timing of fly eclosion. In addition, we evaluated host quality using numbers of larvae or puparia per individual beetle as a measure of quality. The fly parasitized only large carabids (≥15 mm body length); the lengths of fly puparia reached 7.4–10.8 mm during development in beetle abdomens, and larger hosts are likely essential. Of the 18 large carabid species collected in this study, we chose two, Carabus maiyasanus Bates and Leptocarabus procerulus (Bates), because they were large and abundant (87% of total catch). The two carabids had different phonologies; C. maiyasanus was abundant from spring to summer, and its abundance dropped sharply in autumn, while L. procerulus was abundant in autumn and rare from spring to summer except July. Parasitism was observed in all the months from May to November except June, and adult flies eclosed more than once a year (in early summer, late summer, and mid‐autumn), indicating that the species is multivoltine. Host quality of L. procerulus was higher than that of C. maiyasanus. Carabus maiyasanus was mainly used as a host from spring to summer, and L. procerulus was used in autumn. Thus, adult beetles of one or both species are available over most of spring, summer, and autumn, allowing population persistence of this fly species over time.     

Host plant scents attract rolled-leaf beetles to Neotropical gingers in a Central American tropical rain forest

Leaf volatile chemicals are known to reduce herbivory rates by repelling or intoxicating insect herbivores and by attracting the predators and parasitoids of herbivores. However, leaf volatiles may also be used by insect herbivores as cues to locate their host plants. Leaf volatiles are suggested to be important host search cues for herbivores in structurally complex and diverse habitats, such as tropical rain forests. A group of insect herbivores, the rolled-leaf beetles (Coleoptera: Chrysomelidae: Hispinae), have maintained a highly specialized interaction with Neotropical gingers (Zingiberales) for ca. 60 million years. In this study, we explored chemical attraction to host plants under controlled laboratory conditions, using four sympatric rolled-leaf beetle species, Cephaloleia dorsalis Baly, Cephaloleia erichsonii Baly, Cephaloleia fenestrata Weise, and Cephaloleia placida Baly. For each beetle species, we investigated (i) whether it was repelled or attracted by leaf scents produced by four host and four non-host plant species, including Neotropical gingers in the families Marantaceae, Costaceae, and Zingiberaceae; and (ii) its ability to use scents to detect its host plant. We found that rolled-leaf beetles can detect and are attracted by leaf volatiles from both host and non-host gingers. Additionally, when beetles were simultaneously exposed to leaf volatiles from host and non-host plants, three rolled-leaf beetle species were significantly more attracted by volatiles from their host plants than from non-hosts. Only one of the beetle species was not able to discriminate between host and non-host scents.     

Species diversity and community structure of rove beetles (Coleoptera: Staphylinidae) attracted to dung of sika deer in coniferous forests of southwest Japan

Insect communities of mammal dung have been known as excellent model ecosystems for scientific study. Ecological surveys of diversity and seasonal patterns of coprophilous rove beetles in relation to wild mammals have rarely been conducted, although the high potential species diversity and abundance of the rove beetles are known. In order to investigate biodiversity of these beetles, we analyzed species composition, abundance, feeding guild and seasonality of rove beetles that were attracted to sika deer Cervus nippon dung by using dung‐baited pitfall traps for a 1.5‐year study in two plantations (cypress, cedar) and one secondary natural forest (pine) in Fukuoka Prefecture, southwest Japan. Consequently, saprophagous Anotylus sp. (Oxytelinae) was dominant in all forests. Analyses of feeding guild structure showed the number of individuals were dominated by saprophagous beetles, but the number of species were dominated by predatory beetles. Seasonal effects suggested that the species richness and abundance of rove beetles are possibly regulated by scarabaeoid dung beetles. These findings feature one example of a coprophilous rove beetle community.     

Beetle assemblages of indigenous and alien decomposing fruit in subtropical Durban,South Africa

Ecological theory predicts that insect assemblages on indigenous plants will be more diverse than those on alien plants. However, this theory refers primarily to herbivores, and its applicability to decomposers is unclear. Here, we compare beetle assemblages from the fallen fruit of the two most common plants producing large fleshy fruit at our study site in Durban, South Africa: one indigenous African plant (the toad tree, Tabernaemontana ventricosa, Apocynaceae) and one invasive tropical American one (the granadilla, Passiflora edulis, Passifloraceae), at various stages of the decomposition process, thus spanning a continuum between herbivory and detritivory. Beetles found on the two plants included both alien (some categorized as pests of stored fruit) and indigenous species (including some localized endemics). We found that the mean diversity and abundance were not significantly different between the two plant species (with nine beetles from four morphospecies in the average sample) and that the beetle assemblages from the two plant species largely overlap. Statistical analyses suggested that other factors such as stage of fruit decomposition and seasonality could have greater influence on diversity and abundance than the provenance of the plant species. We conclude that insect–plant interactions in the emerging ecosystems that include indigenous and alien species in both groups are complex and that the importance of interactions between species of different provenances may have previously been underestimated.     

Various population fluctuation patterns of light-attracted beetles in a tropical lowland dipterocarp forest in Sarawak

The population fluctuation pattern of light-attracted beetles was studied from August 1992 to September 1998 (for 73 months) using ultraviolet light-traps set at three vertical levels in a tropical lowland dipterocarp forest in Sarawak, Malaysia. During our study, a general flowering occurred from April to July in 1996, and flowering on a small scale in 1997 and 1998. We analyzed the data for eight scarabaeid and six meloid species, some of which were anthophilous species. Various fluctuation patterns were observed among the beetle species in aspects of both seasonality and correlation with the supraannual phenological pattern. Three large chafer species (Scarabaeidae, Melolonthini) showed a clear seasonal fluctuation pattern with a peak once from March to May every year, the peak monthly catch greatly fluctuating annually. Other scarabaeid beetles did not show such a clear seasonal population pattern and hardly fluctuated annually. Populations of an anthophilous scarabaeid species, Parastasia bimaculata, a specific pollinator of Homalomena propinqua (Araceae), hardly fluctuated, probably because of its response to the constant flowering of its floral hosts. Monthly catches of an anthophilous scarabaeid, Anomala sp., and meloid beetles showed clear supraannual patterns in response to the general flowering and were significantly correlated with the flowering intensity with or without a lag of a month. The fluctuation pattern of meloids suggests a supraannual population fluctuation pattern of their hosts, i.e., megachilid/anthophorid bees. Received: November 9, 1999 / Accepted: February 8, 2000     

Variations in dung beetle assemblages across a gradient of hunting in a tropical forest

Populations of large mammals are severely depleted by hunting in tropical forests, with direct effects on plant regeneration. But indirect consequences on commensal taxa depending on them for food resources, like coprophagous beetles, are less documented. Cascading effects of species loss across Scarabaeinae are expected, with likely significant negative implications for ecosystem functions. We examined dung beetle assemblages using pitfall traps at three rain forest sites in French Guiana ranging from intact mammalian fauna (Nouragues) to moderate (Kaw) and heavy (Matoury) defaunation. The site with the most depauperate mammalian fauna showed significantly lower dung beetle species richness than the two other two sites, which were not different from each other. Mean abundance and biomass per trap were not different across sites whereas community composition strongly differed among sites. A positive correlation was observed between body size and the individual contribution to dissimilarity between Nouragues and Kaw. The species contributing the most to dissimilarity were large. By contrast, one medium-sized species, dominant in Matoury, contributed the most to dissimilarity between Matoury and other sites. Diurnal genera of large tunnellers showed a higher diversity and abundance in Nouragues compared to other sites, whereas a nocturnal genus showed no differences. Large rollers were more abundant in Kaw compared to other sites. None of the groups of small beetles but one were affected by defaunation. Our results suggest that loss of large mammal populations affects dung beetle assemblage structure and causes decreasing abundance or disappearance of large tunnellers species that have a major impact on several dung beetle-mediated ecological processes.     

Microhabitat use and seasonality of the sexually dimorphic West African centaurus beetle Augosoma centaurus

The sexually dimorphic dynastine centaurus beetle, genus Augosoma (Coleoptera: Scarabeidae), is endemic to tropical Africa where two species are found (A. centaurus and A. hippocrates). These beetles are consumed by rural populations, cause damage in plantations and are targets of insect collectors and traders. We present information on size differences and analyzed intersexual niche divergence and seasonality of A. centaurus in seven study sites in three West African countries (Ivory Coast, Togo and Nigeria). We recorded 711 light-attracted and/or opportunistically encountered individuals, as well as another 97 beetles in standardized transect surveys. In the latter, we found the adult sex ratio was equal, but was significantly skewed towards females in light-attracted and/or opportunistically encountered individuals. In a sample of 298 adult beetles, males were significantly larger than females, with almost no size overlap between sexes. Beetle activity was highly seasonal with most animals observed in November, active from 19:00 h to 24:00 h. Differences in habitat use were not significant between sexes, with most individuals observed in secondary forest. Males were found higher on vegetation than females and beetles of both sexes were found on Pandanus and raffia palms. Beetles were larger in sites with more vegetation cover, and there was a significant effect of tree species on body size of both sexes. Study area or country had no effect on any of the studied parameters. Our study confirms that transect surveys without light trapping can be an effective tool for understanding large-sized tropical beetles of similar ecological characteristics.     

Temporal coexistence of dung-dweller and soil-digger dung beetles (Coleoptera, Scarabaeoidea) in contrasting Mediterranean habitats

The western part of the Mediterranean basin is a transitional biogeographical region for the distribution of the representatives of the main guilds of dung beetles; towards the south, Aphodiinae (dung-dwellers) become scarce, whereas northwards Scarabaeinae (soil-diggers) progressively disappear. The number of species in local dung beetle assemblages is enhanced by this double faunistic contribution. Annual dung beetle assemblages were sampled in two sub-Mediterranean sites, which differed by 600 m in elevation, in order to determine the phenological dynamics related to the way of using dung (dung-dwellers/Aphodiinae vs. soil-diggers/Scarabaeinae and Geotrupinae). Aphodiids were active all year round, although they were affected by summer drought and, at high elevation, by the length of the cold season. This reduced activity was related to an impoverishment of Aphodiinae and to reduced temporal segregation between species. In contrast, soil-diggers were not active all year round and showed different species assemblages in the two sites. An extension of the activity period of these beetles was observed due to the occurrence of cold resistant species at high elevation. Our results suggested that the occurrence of soil-diggers seemingly did not affect the seasonality of dung-dwellers; their local abundance showed no negative correlation and, most importantly, phenological differences between dung-dwellers were always significantly higher than the seasonal differences between dwellers and diggers.     

Simplification of a coffee foliage-dwelling beetle community under low-shade management

Coffee agroforests may be structurally and floristically complex and may contain a significant fraction of species from biodiverse and threatened tropical montane forest biotas; hence, understanding the dynamics of tropical forest biodiversity in coffee agroecosystems has emerged as a centrally important area of tropical conservation biology research. We conducted a morphospecies analysis on foliage-dwelling beetles collected from coffee plants on four coffee farms in southern Chiapas, Mexico, to characterize variation in the abundance, species richness, and species composition of this mega-diverse taxon in relation to coffee cultivation system, spatio-temporal variation, and predator removal. We constructed thirty-two cages to exclude birds and bats on four farms, each enclosing 7–10 coffee plants and paired with an adjacent uncaged control plot, and then collected beetles from coffee foliage with D-Vac aspirators in each plot once every 3 months for one year.We classified the 2662 beetles collected into 293 morphospecies, representing 42 families of beetles. Extrapolation and interpolation analyses revealed a very high level of species richness, with no plateau and only a slight leveling trend observed in our species accumulation curves. We found that low-shade systems contain equal or higher beetle abundance, lower species richness, more highly homogenized species composition, and higher abundance of coffee berry borer pests on coffee foliage than do high-shade systems. We observed no effect of flying vertebrate exclusion on the coffee foliage beetle assemblage, but did find significant variation in abundance, species richness, and species composition of coffee foliage beetles across seasons and study sites.The increased beetle biodiversity of high-shade coffee cultivation systems has important implications both for the preservation of native biodiversity in coffee growing regions and for the control of agricultural pests such as the coffee berry borer.     

Host specificity of ambrosia and bark beetles (Col., Curculionidae: Scolytinae and Platypodinae) in a New Guinea rainforest

Abstract.  1. Bark and ambrosia beetles are crucial for woody biomass decomposition in tropical forests worldwide. Despite that, quantitative data on their host specificity are scarce.
2. Bark and ambrosia beetles (Scolytinae and Platypodinae) were reared from 13 species of tropical trees representing 11 families from all major lineages of dicotyledonous plants. Standardised samples of beetle-infested twigs, branches, trunks, and roots were taken from three individuals of each tree species growing in a lowland tropical rainforest in Papua New Guinea.
3. A total of 81 742 beetles from 74 species were reared, 67 of them identified. Local species richness of bark and ambrosia beetles was estimated at 80–92 species.
4. Ambrosia beetles were broad generalists as 95% of species did not show any preference for a particular host species or clade. Similarity of ambrosia beetle communities from different tree species was not correlated with phylogenetic distances between tree species. Similarity of ambrosia beetle communities from individual conspecific trees was not higher than that from heterospecific trees and different parts of the trees hosted similar ambrosia beetle communities, as only a few species preferred particular tree parts.
5. In contrast, phloeophagous bark beetles showed strict specificity to host plant genus or family. However, this guild was poor in species (12 species) and restricted to only three plant families (Moraceae, Myristicaceae, Sapindaceae).
6. Local diversity of both bark and ambrosia beetles is not driven by the local diversity of trees in tropical forests, since ambrosia beetles display no host specificity and bark beetles are species poor and restricted to a few plant families.     

Contrasting diversity dynamics of phoretic mites and beetles associated with vertebrate carrion

Carrion is an ephemeral and nutrient-rich resource that attracts a diverse array of arthropods as it decomposes. Carrion-associated mites often disperse between animal carcasses using phoresy, the transport of one species by another. Yet few studies have contrasted the dynamics of mite assemblages with other insect taxa present at carrion. We examined and compared the changes in abundance, species richness and composition of mite and beetle assemblages sampled at kangaroo carcasses in a grassy eucalypt woodland at four different times over a 6-month period. We found that the majority of mites were phoretic, with the mesostigmatid genera Uroseius (Uropodidae), Macrocheles (Macrochelidae) and Parasitus (Parasitidae) the most abundant taxa (excluding astigmatid mites). Abundance and richness patterns of mites and beetles were very different, with mites reaching peak abundance and richness at weeks 6 and 12, and beetles at weeks 1 and 6. Both mites and beetles showed clear successional patterns via changes in species presence and relative abundance. Our study shows that mesostigmatid mite assemblages have a delay in peak abundance and richness relative to beetle assemblages. This suggests that differences in dispersal and reproductive traits of arthropods may contribute to the contrasting diversity dynamics of carrion arthropod communities, and further highlights the role of carrion as a driver of diversity and heterogeneity in ecosystems.     

Revegetation and its Effect on the Ground-Dwelling Beetle Fauna of Matiu-Somes Island, New Zealand

A study of beetle (Coleoptera) communities was conducted in three revegetated sites of different ages (5, 17, and 100 years) and in a remnant coastal habitat dominated by Muehlenbeckia complexa (a liane) on Matiu‐Somes Island, Wellington Harbor, New Zealand. The 25‐ha island has had a 110‐year history as a pastoral agricultural quarantine station. Beetles were surveyed from May 1997 to April 1998 using pitfall traps. We collected a total of 3,430 adult beetles from 78 beetle species belonging to 22 families. Various environmental factors influencing the distribution of beetles in revegetated habitats were investigated. The most important factors were canopy height and canopy density (functions of vegetation age). Overall, results suggest that as habitat/vegetational heterogeneity increases at a site, beetle diversity and abundance also increase. Thus, older replanted sites contained a greater species richness and abundance of beetles than newly replanted sites. Revegetation is, thus, successfully facilitating the establishment and recolonization of the beetle fauna on Matiu‐Somes Island.     

How many species of host-specific insects feed on a species of tropical tree?

The assumptions on the host specificity of beetles that led Terry Erwin to suggest that there may be over 30 million arthropod species were tested for 10 species of trees and their insect associates at a rainforest site in Papua New Guinea. The data included 391 species and 4696 individuals of herbivorous beetles collected during a one year period using hand collecting, beating, branch clipping, intercept flight traps and pyrethrum knockdown. Insect host specificity was assessed by feeding trials in captivity. The data suggest that between 23 and 37 monophagous leaf-feeding species are most likely to be present in this system, whereas Erwin's method yields an estimate of 138 monophagous species. The major factors responsible for the discrepancy between our observations and Erwin's assumptions appears to be (a) the importance of transient species; (b) the insect fauna that is shared among tree species; (c) some generalist wood-eating species may inflate the apparent species richness of leaf-feeding beetles; and (d) the proportion of specialist species varies significantly among tree species. We conclude that studies reporting the proportion of specialist insect herbivores associated with particular tropical tree species will yield only a portion of the information needed to estimate global arthropod species richness, but may be useful for elucidating certain aspects of food-web ecology in tropical rain forests.     

Factors influencing duiker dung decay in north‐east Gabon: are dung beetles hiding duikers?

We analysed seasonality of dung decay time and the influence of rainfall, leaf fall, beetle attack and moisture on dung decay. Our study was carried out at the Ipassa Reserve, north-east Gabon. We compared the seasonality of dung decay with the seasonality of dung beetle abundance and guild structure. Dung beetle activity was the main factor influencing dung decay in our study site. Decay time was the highest during the main dry season (3.4 days) and the lowest during the short rainy season (0.7 days). Dung decay time was closely related to dung beetle abundance, especially to the abundance of nocturnal beetles. We discuss the implications of such results for duiker survey methods based on dung pellet counts in areas where decay time is extremely short or unknown.     

Using dung beetles to evaluate the effects of urbanization on Atlantic Forest biodiversity

We used dung beetles to evaluate the impact of urbanization on insect biodiversity in three Atlantic Forest fragments in Londrina, Paraná, Brazil. This study provides the first empirical evidence of the impact of urbanization on richness, abundance, composition and guild structure of dung beetle communities from the Brazilian Atlantic Forest. We evaluated the community aspects (abundance, richness, composition and food guilds) of dung beetles in fragments with different degrees of immersion in the urban matrix using pitfall traps with four alternative baits (rotten meat, rotten fish, pig dung and decaying banana). A total of 1 719 individuals were collected, belonging to 29 species from 11 genera and six Scarabaeinae tribes. The most urban‐immersed fragment showed a higher species dominance and the beetle community captured on dung presented the greatest evenness. The beetle communities were distinct with respect to the fragments and feeding habits. Except for the dung beetle assemblage in the most urbanized forest fragment, all others exhibited contrasting differences in species composition attracted to each bait type. Our results clearly show that the degree of urbanization affects Atlantic Forest dung beetle communities and that the preservation of forest fragments inside the cities, even small ones, can provide refuges for Scarabaeinae.     

How do beetle assemblages respond to cyclonic disturbance of a fragmented tropical rainforest landscape?

There are surprisingly few studies documenting effects of tropical cyclones (including hurricanes and typhoons) on rainforest animals, and especially insects, considering that many tropical forests are frequently affected by cyclonic disturbance. Consequently, we sampled a beetle assemblage inhabiting 18 upland rainforest sites in a fragmented landscape in north-eastern Queensland, Australia, using a standardised sampling protocol in 2002 and again 12 months after the passage of Severe Tropical Cyclone Larry (March 2006). The spatial configuration of sites allowed us to test if the effects of a cyclone and those from fragmentation interact. From all insect samples we extracted 12,568 beetles of 382 species from ten families. Beetle species composition was significantly different pre-and post-cyclone although the magnitude of faunal change was not large with 205 species, representing 96% of all individuals, present in both sampling events. Sites with the greatest changes to structure had the greatest changes in species composition. At the site level, increases in woody debris and wood-feeding beetle (Scolytinae) counts were significantly correlated but changes in the percent of ground vegetation were not mirrored by changes in the abundance of foliage-feeding beetles (Chrysomelidae). The overall direction of beetle assemblage change was consistent with increasing aridity, presumably caused by the loss of canopy cover. Sites with the greatest canopy loss had the strongest changes in the proportion of species previously identified in the pre-cyclone study as preferring arid or moist rainforest environments. The magnitude of fragmentation effects was virtually unaltered by the passage of Cyclone Larry. We postulate that in the short-term the effects of cyclonic disturbance and forest fragmentation both reduce the extent of moist, interior habitat.     

Comparative water relations of adult and juvenile tortoise beetles: differences among sympatric species

Relative abundance of two sympatric tortoise beetles varies between drought and 'wet' years. Differing abilities to conserve water may influence beetle survival in changing environments. Cuticular permeability (CP), percentage of total body water (%TBW), rate of water loss and percentage of body lipid content were determined for five juvenile stages and female and male adults of two sympatric species of chrysomelid beetles, the golden tortoise beetle, Charidotella bicolor (F.) and the mottled tortoise beetle, Deloyala guttata (Olivier). There were significant differences in %TBW and lipid content among juvenile stages. Second instars had the greatest difference in CP (37.98 and 11.13 microgcm(-2)h(-1)mmHg(-1) for golden and mottled tortoise beetles, respectively). Mottled tortoise beetles had lower CP and greater %TBW compared with golden tortoise beetles, suggesting that they can conserve a greater amount of water and may tolerate drier environmental conditions. This study suggests that juvenile response to environmental water stress may differentially affect the survival of early instars and thus affect the relative abundance of adult beetles in the field. This is supported by the low relative abundance of golden tortoise beetle larvae in a drought year and the higher abundance in two 'wet' years.