An order-specific monoclonal antibody to Diptera reveals the impact of alternative prey on spider feeding behavior in a complex food web

Generalist predators have the capacity to restrict pest population growth, especially early in the season before densities increase. However, their polyphagous feeding habits sometimes translate into reduced pest consumption when they target alternative prey. An order-specific monoclonal antibody was developed to examine the strength of trophic connections between Diptera, a major category of non-pest prey, and linyphiid spiders in alfalfa. We report the development and characterization of a monoclonal antibody with order-level specificity to Diptera. This antibody elicited strong absorbance to 22 Diptera from 13 families, no false-positive reactivity to non-dipteran invertebrates, and antigen detection periods following prey consumption that were comparable between spiders. Over 900 field-collected females of the linyphiid spiders Erigone autumnalis and Bathyphantes pallidus were screened for Diptera antigen. Significantly more B. pallidus screened positive for Diptera (40%) compared to E. autumnalis (16%), indicating differential reliance on these prey. In parallel with the collection of spiders for gut-content analysis, prey availability was estimated at web sites. The two spiders exhibited different feeding responses to prey availability. Consumption of Diptera by B. pallidus was strongly correlated with Diptera abundance whilst the availability of other potential prey did not influence predation rates. Conversely, E. autumnalis did not prey upon Diptera in proportion to availability, but increased Collembola activity-density reduced dipteran consumption. Integration of molecular gut-content analysis with precise sampling of prey demonstrated how two closely related linyphiid spiders exhibit different feeding responses to the availability of prey under natural field conditions. Elucidating the feeding preferences of natural enemies is critical to effective incorporation of biological control by generalist predators in the management of agricultural pests.     

Estimating predation rates from molecular gut content analysis

Several methods have been published to estimate per capita predation rates from molecular gut content analysis relying on intuitive understanding of predation, but none have been formally derived. We provide a theoretical framework for estimating predation rates to identify an accurate method and lay bare its assumptions. Per capita predation can be estimated by multiplying the prey decay rate and the prey quantity in the predators. This assumes that variation in per capita predation rate is approximately normally distributed, prey decay occurs exponentially, and predation is in steady state. We described several ways to estimate steady state predation, including using only qualitative presence-absence data to estimate the decay rate and in addition, we provided a method for estimating per capita predation rate when predation is not in steady state. We used previously published data on aphid consumption by a ladybird beetle in a feeding trial to calculate the predation rate and compare published methods with this theoretically derived method. The estimated predation rate (3.29 ± 0.27 aphids/h) using our derived method was not significantly different from the actual predation rate, 3.11 aphids/h. In contrast, previously published methods were less accurate, underestimating the predation rate (0.33 ± 0.02 to 1.66 ± 0.8 aphids/h) or overestimating it (3.64 ± 0.30 aphids/h). In summary, we provide methods to estimate predation rates even when variation in predation rates is not exactly normally distributed and not in steady state and demonstrate that the prey decay rate, and not the prey detection period, is required.     

Secondary predation: quantification of food chain errors in an aphid-spider-carabid system using monoclonal antibodies

"Secondary predation" occurs when one predator feeds on a second predator, which has in turn eaten a target prey. Detection of prey remains within predators using monoclonal antibodies cannot distinguish between primary and secondary predation, potentially leading to quantitative and qualitative food chain errors. We report the first fully replicated experiments to measure secondary predation effects, using an aphid-spider-carabid system. Aphids, Sitobion avenae, were fed to spiders, Lepthyphantes tenuis, which were allowed to digest their prey for a range of time intervals. The spiders were then fed to carabids, Poecilus (=Pterostichus) cupreus, which were again allowed to digest their prey for set periods. The anti-aphid monoclonal antibody used to identify S. avenae remains in P. cupreus was one that detected an epitope that increased in availability over the first few hours of digestion, amplifying the signal, extending detection periods and thus increasing the chances of detecting secondary predation. Despite this, and the fact that spiders are known to digest their prey more slowly than many other predators, detection of secondary predation was only possible if the carabids were killed immediately after consuming at least two spiders which were, in turn, eaten immediately after consuming aphids. As this scenario is unlikely to occur frequently in the field it was concluded that secondary predation is unlikely to be a serious source of error during field studies.     

Immunological determination of digestive rates in the syntopic scorpions Urodacus armatus Pocock and Urodacus novaehollandiae Peters

Scorpions have lengthy periods of inactivity, which may be caused either by a long physiological digestion time or predator avoidance or both. We used a quantitative immunological assay to monitor the amount of prey antigen remaining in the hepatopancreas of Urodacus armatus and U. novaehollandiae for 32 days after a meal to test the hypothesis of a long digestion time. In both species, prey antigen concentration in the hepatopancreas increased between 0.25 and 0.5 days after feeding, probably because of incomplete transfer of prey proteins from the large preoral cavity to the hepatopancreas at this stage of digestion. This was followed by a rapid decline, and by 3 days after feeding less than 25% of ingested antigen remained in each species. Small prey residues could still be detected up to 32 days. Prey decay curves in both species were best fitted by a log-log transformation, and were not significantly different. Since digestion is essentially complete after 3 days, it appears that longer periods of post-feeding inactivity are for predator avoidance, not digestion. However, the 32-day detection period exceeds those reported for other invertebrates, and suggests an unusual digestive physiology in scorptions.     

Stomach evacuation rate in the planktivorous Antarctic fish Pagothenia borchgrevinki

Summary Specimens of the Antarctic fish Pagothenia borchgrevinki were collected from just below the sea-ice in McMurdo Sound over the period 5–16 November 1987. The stomach contents of 54 freshly captured fish were analysed and showed very strong similarities with an earlier, more extensive, dietary analysis conducted at the same location (Foster et al. 1987). There was as much variation in stomach contents from fish within a school, as there was between schools, contrary to the expectation that fish within a school would have shared a more common feeding history. Fish were maintained in holding tanks for up to 48 h after capture; groups were sacrificed at 6 h intervals and the stomach contents analysed to determine evacuation rates. Evacuation rates of total stomach contents and individual prey species were fitted with an exponential model of decay. The exponential time constant for decay of stomach contents was 32 h (Table 2), while time constants for individual prey species ranged from 12 h for small prey species to 49 h for the larger crustacea. The feeding rate of P. borchgrevinki on important prey species was calculated from the above data (Table 2). Low feeding rates, and the low numbers of P. borchgrevinki argue against removal by predation as being the explanation for the observed reduction in plankton numbers seen in shallow waters (Foster 1989).     

Changing handling times during feeding and consequences for prey size selection of 0+ zooplanktivorous fish

The interrelationship of fish size, prey size and handling time within a 15-min feeding period was studied in three size groups of 0 + roach, Rutilus rutilus, and bleak, Alburnus alburnus. Four size classes of cladoceran prey were used to measure changes in feeding rate and handling time from initial rapid feeding to sustained feeding. Observed differences in increase of handling time between prey size classes led to a change in the prey profitability ranking of those size classes within the first 2 min of the experiments. A 1-min feeding period is interpreted as reflecting an intermediate motivational status between extreme hunger and satiation. The use of average handling times for this period revealed a substantial change in prey profitability estimates compared to previous studies which used handling times based on short-term (a few seconds up to 1 min) feeding. It is not the largest prey items a fish can handle and swallow that are most profitable, but prey of intermediate size. By this approach a closer fit between expectations derived from optimal foraging theory and empirical data on prey size selection of 0 + zooplanktivorous fish is qualitatively achieved. Optimal prey size was found to be close the mouth gape width in small fish of 15 mm standard length, decreasing to 50% of mouth gape width in fish of 40 mm standard length.     

The feeding rates ofPleurobrachia (ctenophora) andSagitta (chaetognatha), with notes on the potential seasonal role of planktonic predators in the dynamics of north sea zooplankton communities

The zooplankton off the north-east coast of England has been the subject of a number of studies focusing on its productivity. It has also been shown to be representative of the zooplankton of much of the western North Sea. The community contains a number of predatory species, three of which are widely described as ‘voracious’, the ctenophorePleurobrachia pileus, the chaetognathSagitta elegans and the hyperiid amphipodThemisto compressa (≡ Parathemisto gaudichaudi). This study investigates the role of these planktonic predators in this community, with special reference to the seasonal changes in predation pressure. The functional response ofPleurobrachia pileus feeding onAcartia was determined from laboratory experiments. It was found to be linear at prey densities typical of UK coastal waters, although the linear relationship appeared to break down at low and high prey densities. Feeding rate data forSagitta elegans were obtained from gut content analysis and published laboratory derived estimates of digestion time. Of the 1,789 individuals examined 198 (11.1%) had food remains in the gut. A linear relationship betweenSagitta length and prey size was established and the daily feeding rate ofSagitta elegans was estimated to be 0.4 prey items d⁻¹ ind⁻¹. For comparative purposes, the proportion of the copepod standing stock removed bySagitta elegans, Pleurobrachia pileus andThemisto gaudichaudi was estimated for each month of the year. From this model it was shown thatThemisto applied the most predation pressure, andSagitta elegans applied the least predation pressure of the three planktonic predators considered. The impact ofPleurobrachia will be to a large extent offset due to its peak of seasonal abundance coinciding with the zooplankton peak in the summer.     

A method for in situ estimation of prey selectivity and predation rate in large plankton, exemplified with the jellyfish Aurelia aurita (L.)

A method to estimate predation rates of large predatory zooplankton, such as jellyfish and ctenophores, is outlined. Large plankton size allows direct visual tracking of the predator during the process of foraging. The presented method is novel in the sense that it measures predation rate of a specific individual plankton predator in situ.After prey has been evacuated from the gut of an individual predator, the predator is incubated in situ, and observed by SCUBA-divers who recapture the individual after a defined time. Given that this incubation time is shorter than prey digestion time, predation rate can be calculated as increase in gut content over time. Clearance rates for different prey can be calculated from predation rates and prey concentrations in the water, allowing accurate estimates of prey selectivity. Thus, the problem of unknown feeding history and feeding environment, which can otherwise be a problem in prey selectivity studies of in situ-captured predators, is circumvented. Benefits and limitations of the method are discussed.The method was applied to adult medusae of the common jellyfish Aurelia aurita. A large variation in number of captured prey was detected both among individual jellyfish and among the various oral arms and gastric pouches within individuals. Clearance rates varied strongly with prey type. The medusae selected large crustacean prey (cladocerans and copepods/copepodites) over echinoderm larvae and copepod nauplii. Prey distribution within the medusae indicates that both tentacles and oral arms were used as prey capturing sites. Food passage time from prey capturing organs to gastric pouches was estimated.     

Feeding chronology of juvenile piranhas,Pygocentrus notatus,in the Venezuelan llanos

Synopsis During the 1988 rainy season, I studied the 24 h feeding chronology of juvenile (40–68 mm standard length) piranhas, Pygocentrus notatus (Characidae: Serrasalminae) from a natural population inhabiting a small savanna stream in Apure State, Venezuela. Stomach contents analyses, supported by laboratory determinations of digestion rate, showed that these fish are primarily diurnal carnivores. Predatory activity on 4–5 August 1988 increased markedly after sunrise, peaked around 1100 h, and essentially stopped after sunset. Means of stomach content weight-to-fish weight ratios among the periods sampled were significantly different. Small fish were the major prey at all hours (81% of total prey volume). Underlying factors responsible for the observed 24 h feeding patterns were not investigated, but avoidance of predation by adult piranhas, which were very active near sunset, may have been important.     

Development of a Monoclonal Antibody for the Detection and Quantification of Predation on Slugs within the Arion hortensis agg. (Mollusca: Pulmonata)

The Arion hortensis agg. (Mollusca: Pulmonata) are major slug pests of agriculture and horticulture throughout much of the temperate World. A monoclonal antibody was created that could specifically identify and quantify the remains of these slugs within the carabid predator Pterostichus melanarius Illiger, a polyphagous species found in arable crops in Europe and North America. The antibody was shown to be specific for the two species of pest slug within this species aggregate, Arion distinctus Mabille and A. hortensis Férussac, and did not cross-react with any other invertebrates tested, including other slugs in the same genus. It proved to be highly sensitive in an enzyme-linked immunosorbent assay. The mean detection period for the remains of A. distinctus in predator foregut samples was 3.28 days at 16°C. However, A. distinctus remains could be identified in male carabids for 30% longer than in females, emphasizing the importance of separate analyses. The value of the antigen half-life as a measure of the detection period was questioned because analysis of covariance showed that the regression slopes for antigen decay were not significantly different between the two sexes, giving very similar half-lives (approx 18.5 h for females and 19 h for males). Calculated quantities of soluble slug proteins in predator foreguts declined more rapidly over time than concentrations, allowing separate assessment of the importance of these two variables on detection periods. It was concluded that a valuable new antibody had been created and characterized, which can be used for the analysis of predation in the field.     

The feeding ecology of the pit-making ant lion larva,Myrmeleon bore: Feeding rate and species composition of prey in a habitat

The prey species composition and feeding rate of the pit-making ant lion larva,Myrmeleon bore Tjeder, which inhabits open sandy areas, were examined. Not less than 30 prey species, most of which were ants, were collected during a research period of 1.5 years. First instar larvae most often (81.1%) captured ants. Although 3rd instar larvae captured larger-sized prey than individuals of any other instar, they also captured small prey. The feeding rate of 3rd instar larvae was estimated by using the frequency of observed predation (FOP; (no. of ant lions handling a prey)/(total no. of pits observed)), the prey-handling time and the rhythm of daily foraging activity. FOP ofM. bore larvae was constant on the whole from spring to autumn. It was estimated that each captured 1.25 prey per day on average during this period. This estimate, however, was the feeding rate for days on which there was no rain. Assuming that the larvae cannot capture prey due to pit destruction when there is more than 10 mm of rainfall per day, the figure was reduced to 1.03 prey/day. The estimated feeding rate was evaluated with reference to larval foraging behavior.     

The influence of time and temperature on molecular gut content analysis： Adalia bipunctata fed with Rhopalosiphum padi

Gut content analysis is a useful tool when studying arthropod predator-prey interactions. We used polymerase chain reaction （PCR） technique to examine how detection of prey DNA in the gut content of predators was influenced by digestion time and temperature. Such knowledge is critical before applying PCR-based gut content analysis to field collected predators. Larvae of the two-spotted ladybeetle （Adalia bipunctata L.） were fed with the bird cherry-oat aphid （Rhopalosiphum padi L.） at either 21℃ or 14℃. After consuming one aphid, the predators were allowed to digest the prey for a range of time periods up to 24 hours. The influence of temperature on A. bipunctata feeding behavior was also recorded. From the fed larvae, total DNA was extracted and PCR reactions with R. padi specific primers were run. The number ofA. bipunctata that tested positive for R. padi DNA was negatively related to the length of digestion time. Temperature influenced larval feeding behavior but did not have a significant effect on R. padi DNA detection. After pooling the data from both temperature treatments we estimated the time point when R. padi DNA could be amplified from 50% of the fed A. bipunctata by PCR to be 4.87 hours. With such a rapid decrease in prey DNA detection success, positive PCR reactions will most likely be the result of predation events occurring shortly before capture. If a defined digestion temperature range has proven not to influence prey detection, PCR data obtained from predators collected within that particular range can be interpreted in the same way.     

Rates of predation on mammals by gombe chimpanzees, 1972–1975

Rates of chimpanzee predation on mammals are calculated using data on 75 kills recorded during focal observation in Gombe National Park, Tanzania, from January 1972 to April 1975. The chimpanzees were members of two study communities (Kanyawara, or Northern, and Kahama, or Southern, community), and were observed as focal individuals for 14,583 hr by more than 30 researchers and field assistants working in pairs. The rate of predation by females was too low to allow reasonable estimates. For males, the mean rate of killing during the study period was 0.31 kills per male per 100 hr (N=17 males), or 4.65 kills per 100 hr in the two communities. In contrast to results from Mahale Mountains, there was no difference in predation rate between wet and dry seasons. However, predation rates varied over time, increasing by four times between the first three and last four seasons of the sample period. In an average year the 15 adult and subadult male chimpanzees are calculated to have killed 204 prey per year in an area of 16 km², varying between 99 and 420 prey per year in periods of low and high predation rate. Red colobus were the most frequent prey, followed by bushpig and bushbuck. Predation rates varied greatly on different prey species, and were not related to either the proportion of time spent within 200 m of male chimpanzees, or to their population densities. In relation to encounter rates and population density, baboons, blue monkeys, and redtail monkeys were killed at a fraction of the rate of red colobus monkeys, which suffered severe mortality from chimpanzee predation. Predation on bushpig and bushbuck also appears to have been high in relation to population density. The amount of food provided by predation is estimated to have averaged 600 kg per year for chimpanzees in the two communities (totalling 14–17 adult or subadult males, 18–20 adult of subadult females, and about 19 infants or juveniles). This suggests that adult males consumed around 25 kg of meat per year, although any average figure undoubtedly masks considerable individual variation. Present data suggest that chimpanzees in Gombe and Tai National Park, Ivory Coast, prey on mammals at rates higher than other populations.     

Density-dependent effects of multiple predators sharing a common prey in an endophytic habitat

Multiple predator species feeding on a common prey can lead to higher or lower predation than would be expected by simply combining their individual effects. Such emergent multiple predator effects may be especially prevalent if predators share feeding habitat. Despite the prevalence of endophagous insects, no studies have examined how multiple predators sharing an endophytic habitat affect prey or predator reproduction. We investigated density-dependent predation of Thanasimus dubius (Coleoptera: Cleridae) and Platysoma cylindrica (Coleoptera: Histeridae) on a bark beetle prey, Ips pini (Coleoptera: Scolytidae), in a laboratory assay. I. pini utilize aggregation pheromones to group-colonize and reproduce within the stems of conifers. T. dubius and P. cylindrica exploit these aggregation pheromones to arrive simultaneously with the herbivore. Adult T. dubius prey exophytically, while P. cylindrica adults enter and prey within the bark beetle galleries. Larvae of both predators prey endophytically. We used a multiple regression analysis, which avoids confounding predator composition with density, to examine the effects of varying predator densities alone and in combination on herbivore establishment, herbivore reproduction, and predator reproduction. Predators reduced colonization success by both sexes, and decreased I. pini reproduction on a per male and per female basis. The combined effects of these predators did not enhance or reduce prey establishment or reproduction in unexpected manners, and these predators were entirely substitutable. The herbivores net replacement rate was never reduced significantly below one at prey and predator densities emulating field conditions. Similar numbers of each predator species emerged from the logs, but predator reproduction suffered from high intraspecific interference. The net replacement rate of P. cylindrica was not affected by conspecifics or T. dubius. In contrast, the net replacement rate of T. dubius decreased with the presence of conspecifics or P. cylindrica. Combinations of both predators led to an emergent effect, a slightly increased net replacement rate of T. dubius. This may have been due to predation by larval T. dubius on pupal P. cylindrica, as P. cylindrica develops more rapidly than T. dubius within this shared habitat.     

Tracking predator density dependence and subterranean predation by carabid larvae on slugs using monoclonal antibodies

1. Subterranean carabid larvae are more numerous than surface‐active adults, yet very little is known about their ecological significance, dietary preferences or ability to regulate populations of prey species, particularly pests. Part of the reason for this is that predator–prey interactions beneath the soil are almost impossible to observe. 2. Extensive field studies have shown that adult Pterostichus melanarius (Illiger) can affect the temporal and spatial dynamics of their slug prey. However, if larvae too are feeding on slugs, this could radically affect overall predator–prey dynamics. 3. We tested the hypotheses that P. melanarius larvae would kill and consume two slug species, Deroceras reticulatum Müller and Arion intermedius Normand, under laboratory and semi‐field conditions, and that there would be no significant difference in rates of predation on these slug species. 4. A new monoclonal antibody was developed that was capable of detecting the presence of slug proteins in the guts of P. melanarius larvae. 5. Pterostichus melanarius larvae killed both A. intermedius and D. reticulatum in the laboratory, feeding to a greater extent, and growing more rapidly, on the latter. The larvae were equally effective at reducing numbers of both slug species in a crop of wheat grown in semi‐field mini plots, but predation was affected by density‐dependent intra‐specific competition amongst the beetle larvae. 6. Future modelling of the dynamic interactions between carabids and slugs will need to take into account predation by larvae.     

Influence of larval dietary supply on the food consumption, food utilization efficiency, growth and development of the lacewingChrysoperla carnea

In order to derive quantitative estimates of predation rate from serological gut analysis data, one must have an estimate of the interval during which a meal can be detected after feeding. In practice this has turned out to be ‘D_max,’ defined as ‘...the time from finishing a meal until that meal could just no longer be detected in any individuals.’ However D_max substitutes an absolute limit for what is really a continuous variable with significant variation. We examined this problem in a study of the detectability ofHelicoverpa zea Boddie (Lepidoptera: Noctuidae) fifth instar remains in the guts ofPolistes metricus Say (Hymenoptera: Vespidae). Wasps were maintained onTrichoplusia ni (Hübner) (Lepidoptera: Noctuidae) fifth instars before being fed a singleH. zea fifth instar. They were killed and frozen at 0, 24, 48 and 96 h intervals, with those held for more than 24 h fed a singleT. ni fifth instar at 24 h intervals in order to simulate continued feeding. Wasp abdomens were assayed by immunodot, using a monoclonal antibody toH. zea arylphorin. There was a logarithmic decay in the proportion ofP. metricus positive over time, a singleH. zea fifth instar meal having a detectability half-life of 19.4 h at field temperatures. If prey antigen detectability decays exponentially, then a detectability half-life is a more appropriate unit of detectability than an absolute detectability period.     

生态因子对红螯相手蟹捕食毛蚶苗种的影响

敌害生物的捕食在控制海洋底栖生物群落的丰度和组成中起着关键性的作用。以红螯相手蟹(Sesarma haematocheir)和毛蚶(Scapharca subcrenata)为试验对象,研究了红螯相手蟹的密度、规格、性别,以及毛蚶的密度、规格、海水温度和底质条件对毛蚶苗种存活的影响。结果表明,蟹表现出了第二种类型的功能反应,高密度底播毛蚶苗种可以显著提高成活率;当毛蚶苗种壳长达到20mm以上时,蟹的摄食速率显著下降;随着蟹个体的增大,其摄食速率显著增加,毛蚶的存活率下降;当蟹的密度逐渐增加的时候,同种个体之间的干扰竞争显著提高了毛蚶存活率;雄蟹凭借强有力的螯导致了更多毛蚶苗种的死亡;海水温度较低的春季和秋季底播毛蚶苗种可以显著提高成活率;底质条件的复杂性和异质性为毛蚶的存活提供了"庇护空间",从而减少了敌害生物捕食所带来的损失。     

Digestion rate in relation to starvation in the larva of a carabid predator, Poecilus cupreus

Prey antigen levels were determined by a quantitative enzyme-linked immunosorbent assay in larvae of a carabid predator, Poecilus cupreus L. under laboratory conditions. We determined prey consumption and rate of prey protein decay in larvae having starved for different periods. Prey consumption increased exponentially over 7 days of starvation. The rate of prey immunoreactive material decay seemed to be logarithmic, similar in larvae which had starved for different periods. Most of the digestion took place in the first 3 days period after feeding, irrespective of the amounts ingested. The rate of decay increased with increasing period of starvation. There were also signs of food retention in the alimentary canal in larvae which starved longer.

---

Zusammenfassung Mit eine quantitativen enzymabhängigen Immunoabsorptionstest wurde immunoreaktives Material aus Beutetieren als Eiweissgehalt (IRM/P) in Larven eines polyphagen räuberischen Carabiden, Poecilus cupreus, bestimmt. Wir bestimmten den Beuteverzehr und die Geschwindigkeit des IRM/P Abbaus bei Larven, die während verschiedener Zeit gehungert hatten. Der Beuteverzehr nahm exponentiell zu über 7 Tage Hunger. Die Geschwindigkeit des Beute- IRM/P Abbaus schien logarithmisch. Die Beuteaufnahme nahm fast zwanzigfach zu über 7 Tage Hunger von 2.7 ng auf 50.2 ng IRM/P/10 Mikroliter Larvenextrakt. Der grösste Teil der Verdauung erfolgte am zweiten bis dritten Tag nach der Nahrungsaufnahme, unabhängig von der verdauten Menge. Das Niveau 4 Tage nach der Fütterung zeigte, dass Larven, die vorgängig 7 Tage gehungert hatten, 5.0 ng IRM/P/10 Microliter Extrakt zurückhielten; dies war mehr als die Aufnahmemenge nichthungernder Larven. Die Verdauungsgeschwindigleit nahm zu mit der Dauer des Hungerns, doch wurde auch mehr Beute im Nahrungskanal zurückgehalten.

     

Amplified detection, using a monoclonal antibody, of an aphid-specific epitope exposed during digestion in the gut of a predator.

Monoclonal antibodies are invaluable tools for identifying and quantifying prey remains in the fore-guts of predators. However, they must be target-specific, detect an epitope that is well replicated within the prey (to enhance assay sensitivity) and, critically, recognise a site that can resist digestion. A monoclonal antibody is reported that proved to be aphid-specific and capable of detecting, and accurately identifying, as little as 16.5 ng of aphid protein within a heterologous mixture of invertebrate material. The antibody was selected by screening hybridoma lines for antibodies that bound with semi-digested aphid proteins. The antibody detected an epitope that was found, against expectation, to significantly increase in concentration with time (by approx. 50% over 6 h) in the gut of the carabid predator Pterostichus melanarius. The resultant extended antigen detection period and half-life, and the high specificity of this antibody, showed it to be an enhanced tool for studying interactions between aphids and their predators in the field. It was concluded that the antibody was initially generated to a surface epitope on a high molecular weight native protein (> 200 kD). This epitope, however, was then either replicated on internal sites progressively revealed by digestion, or new epitopes became available as the conformation of the protein changed during digestion.