Suitability of Asian citrus psyllid, Diaphorina citri, as prey for ladybeetles

Given the apparent importance ofladybeetles as biological control agents of theinvasive Asian citrus psyllid, Diaphorinacitri Kuwayama (Homoptera: Psyllidae), aseries of experiments were undertaken to assessthe nutritional suitability of this pest as aprey item. Five species of Coccinellidae wereshown to develop successfully on a diet ofpsyllid nymphs and four species produced viableeggs. Eggs of the flour moth, Ephestiakuehniella Zeller (Lepidoptera: Pyralidae)were used as a reference diet. Larvae of Curinus coeruleus Mulsant, Cyclonedasanguinea L., Exochomus childreniMulsant, Harmonia axyridis Pallas, andOlla v-nigrum Mulsant all had survival ona diet of D. citri nymphs not differentfrom 100%, although developmental times wereextended and adult dry weights were reducedrelative to the Ephestia egg diet. Species were ranked (highest to lowest) forlarval performance on the D. citri dietrelative to the Ephestia egg diet as:E. childreni, 0.85;O. v-nigrum,0.82; C. coeruleus, 0.80;H.axyridis, 0.71;C. sanguinea, 0.48. Most females of C. sanguinea ceasedoviposition on the second day followingtransferal to the D. citri diet, but thefecundity and fertility of females of the otherspecies were not different from those feedingon Ephestia eggs. Generation times onthe Ephestia egg diet at 24°C(time to egg hatch + larval developmental time+ pupation time + adult prereproductive period)were (mean ± SEM): C. coeruleus, 56.7± 1.32 d;C. sanguinea, 28.0 ±0.88 d;E. childreni, 60.8 ± 1.96 d;H. axyridis, 32.2 ± 1.47 d;O.v-nigrum, 25.8 ± 1.12 d. Adult females ofC. coeruleus, H. axyridis and O.v-nigrum consumed the most psyllids in oneh, C. sanguinea was intermediate, andE. childreni consumed the least.     

Cloning and characterization of cDNA probes for the analysis of metallothionein gene expression in the Mediterranean bivalves: <Emphasis Type="Italic">Ruditapes decussatus</Emphasis> and <Emphasis Type="Italic">Cerastoderma glaucum</Emphasis>

cDNA probes have been developed for subsequent use in monitoring the cadmium exposure of the clam Ruditapes decussatus and the cockle Cerastoderma glaucum using metallothionein (MT) gene expression in different tissues of these species. Two partial MT cDNAs were isolated from Ruditapes decussatus and Cerastoderma glaucum. The identification of the nucleotide sequences showed that the cDNAs consist of 480 bp coding 72 amino acid proteins containing 21 cysteine residues organized in Cys–X–Cys motifs as classically described for MTs. The induction of MT gene expression in CdCl₂ treated bivalves was confirmed by dot blot analysis and suggests a potential specific tissue expression rate.     

Rb-Cs ratio as an indicator of fish diet in lakes of the Patagonia, Argentina

The ratios of Rb to Cs contents were studied in five fish species from seven lakes located in the Patagonia Andean Range, Argentina in order to trace fish diet. The species studied were native velvet catfish (Diplomistes viedmensis) and creole perch (Percichthys trucha), and exotic brown trout (Salmo trutta), rainbow trout (Oncorhynchus mykiss), and brook trout (Salvenilus fontinalis). Rainbow trout specimens from two farms were also studied, as well as fish food items and native mussels (Diplodon chilensis). Rb and Cs concentrations were determined by instrumental neutron activation analysis. A positive correlation of Cs concentration in the muscle of velvet catfish with fish length was observed, probably associated with the long biological half-life of this element in this species, whereas the Rb concentration remained constant, hence inhibiting the use of Rb-Cs ratios as a tracer in this case. Seasonal variations observed for rainbow trout and Cs concentration background bias in one of the lakes studied are also a limiting factor to the use of Rb-Cs ratios as a diet tracer. Rb-Cs ratios allowed clear differentiation of rainbow trout raised in farms from the natural specimens that lived in the same environment, in agreement with Rb-Cs ratios determined in both diets. Rb-Cs ratios in rainbow trout showed significant differences between Rivadavia and Futalaufquen lakes compared to Moreno and Nahuel Huapi lakes, which could be associated with a higher participation of plankton in the diet in the first case. No relevant variations in Rb-Cs ratios of brown trout were observed, probably because of the similarity in the diet.     

Negative dietary effects of Colorado potato beetle eggs for the larvae of native and introduced ladybird beetles

Aphidophagous ladybird beetles (Coleoptera: Coccinellidae) are attracted to and feed heavily on aphids, but many species will also feed opportunistically on other prey that they encounter. In potatoes (Solanum tuberosum L.) in Washington State, USA, coccinellids feed on both green peach aphids (“GPA,” Myzus persicae Sulzer) and eggs of the Colorado potato beetle (“CPB,” Leptinotarsa decemlineata Say). The guild of aphidophagous ladybirds includes two native species, Hippodamia convergens Guérin-Méneville and Coccinella transversoguttata Brown. Recently, an introduced species, Coccinella septempunctata L., has invaded and apparently displaced its native congener. A second exotic, Harmonia axyridis Pallas, has colonized the area and is becoming more abundant. We compared larval development of each species on a monotypic diet of GPA, a monotypic diet of CPB eggs, or a mixed diet of both GPA and CPB eggs. Our goal was to answer two questions: (1) do larvae of the four ladybird species benefit from including CPB eggs in their diet and (2) do the four ladybird species differ in their ability to utilize CPB eggs as prey? No larva of any species completed development on a pure diet of CPB eggs, and survivorship was highest for all species when they fed on a pure diet of GPA. One native species, H. convergens, and one exotic species, H. axyridis, exhibited significantly lower survivorship on a mixed diet of both CPB eggs and GPA, compared to a pure GPA diet; H. axyridis also took longer to develop from egg to adult when both prey were provided. Survivorship of the two Coccinella spp. was not altered by the inclusion of CPB eggs with GPA, although CPB eggs lengthened the development time of C. transversoguttata. Adult size was not consistently affected by diet for any of the coccinellids. Overall, no ladybird species benefited from the inclusion of potato beetle eggs in its diet. The two Coccinella species responded similarly to the inclusion of CPB eggs, and so we would not expect any difference in the success of coccinellid larval development in potato fields following the replacement of C. transversoguttata by C. septempunctata. Hippodamia convergens and H. axyridis, the two species whose survivorship was depressed by combining CPB egg and aphid prey, were also the two species that consumed the greatest number of CPB eggs during successful larval development. A comparison of total egg consumption by each species cohort suggested that displacement of the other species by H. axyridis would not alter CPB biological control, because the higher per capita feeding rate by H. axyridis larvae compensated for individuals’ greater mortality risk on a diet including CPB eggs.     

A laboratory study on the demography and competition of three species of littoral cladocerans from Lake Huetzalin,Xochimilco, Mexico

Lake Huetzalin (Xochimilco) is a shallow waterbody in Mexico City with a dominance of the littoral cladocerans Simocephalus vetulus, Alona rectangula, and Pleuroxus aduncus. Here, we present data on the life table and population dynamics of these three cladoceran species on two types of diets (alga Scenedesmus acutus and detritus). We also analyzed the effect of competition on population growth using Scenedesmus, which proved to be the better diet than detritus. We hypothesize that feces of the larger cladoceran species (S. vetulus) could be a food source for the smaller taxa (A. rectangula and P. aduncus). Experiments were conducted in 100 ml beakers with 50 ml of medium in each at a temperature of 23 ± 1°C. We studied the demography of three test species using two food types with four replicates for each treatment in the life table experiments. Based on the data thus obtained we further studied the competition between the cladocerans on a diet of Scenedesmus. The maximal growth rates obtained for P. aduncus, S. vetulus, and A. rectangula fed Scenedesmus acutus were: 0.1, 0.3, and 0.5 d⁻¹, respectively. Among the test species, S. vetulus had the highest survivorship of 77 days when cultured on detritus and P. aduncus the lowest of 20 days on Scenedesmus. The gross reproductive rate (offspring female⁻¹ lifespan⁻¹) ranged from 6 neonates in Pleuroxus to 160 in Simocephalus per female. From the competition experiments conducted using alga as the diet, we observed that A. rectangula and, especially P. aduncus, had higher growth rates in the presence of S. vetulus than in the controls. This facilitation could be one of the reasons for higher species diversity in the littoral of water bodies.     

Distribution,abundance, and feeding of a disjunct population of lady crab in the southern Gulf of St. Lawrence,Canada

The lady crab (Ovalipes ocellatus) is one of the most common native species of swimming crab (Portunidae) of the Atlantic Coast of North America but most populations occur south of Cape Cod, Massachusetts. There is a disjunct population in Northumberland Strait (southern Gulf of St Lawrence), which was the focus of this study. Adult lady crabs were collected by trawling in water >4 m deep from May to October 1999 to 2005 to determine abundance, distribution, and diet. Lady crab occurred only in a small area (about 2,500 km²) in the central part of Northumberland Strait where bottom water temperature was >18°C during summer, and the substrate was mainly sand or sandy gravel. Male lady crab attained a maximum carapace width (CW) of 112 mm compared to 92 mm CW for females. The summer and autumn diet consisted mainly of infauna. The principal prey (each >5% of diet by weight) were: small bivalve molluscs (primarily Atlantic razor clam Siliqua costata and Macoma sp.; 43%), small rock crab (Cancer irroratus; 13%), polychaetes (11%), fish remains (9%), and small lady crab (9%). All stomachs collected during May (water temperature ≤10°C) were empty. There was little evidence of any difference in feeding intensity between 0700 h and 1900 h.     

Fruit diet of Alouatta guariba and Brachyteles arachnoides in Southeastern Brazil: comparison of fruit type, color, and seed size

Fruit is an important food resource for neotropical primates. In this study I compare the fruit diet of sympatric brown howlers (Alouatta guariba) and southern muriquis (Brachyteles arachnoides). Feeding behavior was studied over 12 months and fruit species consumed were identified and assigned to the categories fruit type, fruit color, and seed size. Observed-fruit feeding records were compared with expected records determined from local availability of the fruit of the tree species. I also determined dietary overlap. Fruit consumption occupied 8 and 12% of the feeding time of A. guariba and B. arachnoides, respectively. Fruit from eight tree species were consumed by the former and fruit from twenty-two species by the latter. Patterns of fruit selection of A. guariba and B. arachnoides varied widely. Although howlers and muriquis converge behaviorally by selecting fruit with common attributes (fleshy/unprotected, violet and brown/black-colored), unlike A. guariba, B. arachnoides fed on immature seeds of fleshy/protected and dry fruit. Large seeds were ingested, and defecated intact, by B. arachnoides only. There was little overlap of fruit diet even within categories that had been selected by both, suggesting that dietary divergence is occurring at the interspecific level. Different resource exploitation probably mediates the coexistence of A. guariba and B. arachnoides in low diversity, semideciduous forests, where the environment imposes narrow limits on primate food choices.     

Microspore embryogenesis and the development of a double haploidy protocol for cow cockle (Saponaria vaccaria)

Factors affecting microspore embryogenesis of cow cockle (Saponaria vaccaria) were evaluated including donor plant growing conditions, genotype, bud size, density, medium composition, and culture conditions. Of the two donor plant (day/night) temperature regimes evaluated (10/5°C and 20/15°C), plants grown at 20/15°C were the most embryogenic. An embryogenic frequency of greater than 350 embryos/100 buds was observed in the most embryogenic genotype, cv. ‘White Beauty’. Buds from 3–9 mm in length were evaluated for their embryogenic potential; buds that were 4–7.9 mm produced the most embryos/100 buds. Of all the media compositions evaluated, NLN medium with 15% sucrose resulted in the most embryos. Cow cockle microspores required an initial period of 32°C for 3 days for production of microspore-derived embryos (MDEs).     

Sodium polyacrylamide polyacrylate, a gelling agent in diets for cabbage looper, omnivorous looper and western avocado leafroller

Ingredient substitutions for agar or carrageenan in artificial diets for lepidopterous larvae were evaluated. A sodium polyacrylamide polyacrylate gelling agent, Water-Lock G-400, was compared with agar for solidifying diets of the cabbage looper, Trichoplusia ni (Hübner), omnivorous looper, Sabulodes aegrotata (Gueneé), and the western avocado leafroller, Amorbia cuneana Walsingham. Water-Lock G-400 is considerably less expensive than agar or carrageenan, it does not require heating to gel, and it is made from a dependable supply of agricultural starch. Sabulodes aegrotata pupae from larvae reared on agar were significantly heavier than those reared on Water-Lock G-400. However, the remainder of the variables observed (larval survival, developmental times, fecundity, sex ratio and pupal weights for A. cuneana and T. ni) were all independent of diet. Decreasing the total amount of ingredients in a Water-Lock-G-400 diet produced fewer and smaller T. ni pupae than did an agar diet when the larvae were reared using a mass production protocol. However, these lower values were still above acceptable levels for mass production and reduced the cost of diet production by 65%.Further ingredient substitutions impaired larval development (i.e., replacing pinto beans with soy protein or combinations of soy protein and -cellulose), while others did not (i.e., excluding pinto beans and reducing water content and replacing pinto beans with -cellulose or corn cob grits). Moisture control by adding corn cob grits to diets increased the yield of pupae, while removing water from diets increased survivorship and the yield of pupae.     

Effect of CryIC toxin from Bacillus thuringiensis on larval feeding behavior of Spodoptera exigua

The lack of data on the effect of Bacillus thuringiensis (B.t.) toxins on larval feeding behavior of the pest Spodoptera exigua (Hübner) (Noctuidae: Amphypyrini) prompted us to investigate the effect of three delivery systems of CryIC, a commercial formulation, inclusion bodies, and the activated CryIC toxin. The commercial formulation was the least and CryIC toxin the most lethal form to neonates of susceptible colonies. All but two of the treatments in choice tests with neonates and third instars showed significant avoidance of B.t. treated diet, with greater proportion of larvae from susceptible (UCR-S and AUBURN-S) and resistant (AUBURN-R) colonies on untreated diet than on diet treated with any of the CryIC forms and concentrations tested. Furthermore, third instars consumed significantly more control than treated diet for all CryIC forms, colonies and concentrations. The avoidance of CryIC toxin by neonates and third instars strongly suggests that CryIC, which also is present in the commercial formulation and in the inclusion bodies, is responsible for eliciting avoidance behavior by S. exigua larvae. Behavioral observations of third instars in a no-choice test on either treated or control diet indicated that questing behavior in susceptible larvae appears to be positively related with presence of CryIC toxin in the diet. Furthermore, resistant third instars were on the whole more active than susceptible thirds on both treated and control diet. Resistant thirds raised on CryIC treated diet (AUBURN-RC) spent more time eating treated diet than resistant larvae raised on control diet (AUBURN-R), suggesting that diet conditioning plays an important role on feeding behavior of S. exigua. The implications of these results are discussed.     

The effect of Euglena viridis on immune response of rohu, Labeo rohita (Ham.)

The study evaluated the effect of dietary doses of Euglena viridis on the immune response and disease resistance of Labeo rohita fingerlings against infection with the bacterial pathogen Aeromonas hydrophila. L. rohita fingerlings were fed with diet containing 0 (Control), 0.1 g, 0.5 g, 1.0 g Euglena powder kg⁻¹ dry diet for 90 days. Biochemical (serum total protein, albumin, globulin, albumin:globulin ratio), haematological (WBC, RBC, haemoglobin content) and immunological (superoxide anion production, lysozyme, serum bactericidal activity) parameters of fish were examined after 30, 60 and 90 days of feeding. Fish were challenged with A. hydrophila 90 days post-feeding and mortalities were recorded over 10 days post-infection. The results demonstrate that fish fed with Euglena showed increased levels of superoxide anion production, lysozyme, serum bactericidal activity, serum protein and albumin (P < 0.05) compared with the control group. Following challenge with A. hydrophila less survivability was observed in the control group (56.65%) than the group fed the experimental diets. The group fed 0.5 g Euglena kg⁻¹ dry diet showed the highest percentage survival (75%). These results indicate that Euglena stimulates the immunity and makes L. rohita more resistant to A. hydrophila infection.     

A comparative study of the food niches of lake-dwelling triclads and leeches

The food niches of four species of triclads and three species of non-parasitic leeches living in the littoral zone of British lakes of different trophic status were investigated, over one year, using a serological technique. Antisera against ten potential prey groups were employed. The basic data were adjusted to compensate for differences in predator size and seasonal changes in field temperatures. Data on two of the leech species have been presented elsewhere, but comparisons of the diet of all seven predator species are made in this paper. Much overlap in diet between the various predator species occurs, but, with one exception, each of the genera has a major food resource. The Polycelis spp. feed extensively on oligochaetes, Dugesia polychroa on molluscs, Dendrocoelum lacteum on Asellus, Erpobdella octoculata on chironomids and Glossiphonia complanata on molluscs. Helobdella stagnalis is a generalist feeder. Problems of coexistence of the leech species, and of the leech and triclad species are discussed.     

Effects of glucose-supplemented diets on food intake, nymphal development, and fecundity of glucose-averse, non-glucose-averse, and heterozygous strains of the German cockroach,Blattella germanica

Life history parameters were determined for glucose-averse (glu/glu), wild-type (glu+/glu+) and heterozygous (glu/glu+) genotypes of Blattella germanica (L.) (Blattodea: Blattellidae) fed diets supplemented with glucose. Glu/glu nymphs consumed less glucose-supplemented diet, gained less weight, developed slower and had a lower rate of survival than glu/glu nymphs fed the same diet without added glucose, or glu+/glu+ and glu/glu+ fed either diet. Prior to formation of the first oötheca, female glu/glu consumed less glucose-supplemented diet per day than glu+/glu+ and glu/glu+, which presumably delayed egg case production. Oötheca-bearing glu/glu and glu/glu+ females consumed less glucose-supplemented diet than glu+/glu+ females. Despite a difference in female total diet intake, there was no effect of diet or genotype on fecundity. However, the intrinsic rate of increase (r) for glulglu on unsupplemented diet was less than that of glu+/glu+ and glu/glu+, suggesting that individuals with both glu alleles may be at a selective disadvantage in environments lacking diets containing glucose plus a toxicant.     

Behavioral Ecology of Sympatric Chimpanzees and Gorillas in Bwindi Impenetrable National Park,Uganda: Diet

Via a field study of chimpanzees (Pan troglodytes schweinfurthii) and gorillas (Gorilla gorilla beringei) in Bwindi Impenetrable National Park, Uganda, we found that their diets are seasonally similar, but diverge during lean seasons. Bwindi chimpanzees fed heavily on fruits of Ficus sp., which were largely ignored by the gorillas. Bwindi gorilla diet was overall more folivorous than chimpanzee diet, but was markedly more frugivorous than that of gorillas in the nearby Virunga Volcanoes. During 4 mo of the year Bwindi gorilla diet included more food species than that of the chimpanzees. Three factors in particular—seasonal consumption of fibrous foods by gorillas, interspecific differences in preferred fruit species, and meat consumption by chimpanzees—contributed to dietary divergence between the two species. When feeding on fruits, gorillas ate Myrianthus holstii more frequently than chimpanzees did, while chimpanzees included more figs in their annual diet. Chimpanzee diet included meat of duikers and monkeys; gorilla frequently consumed decaying wood.     

The importance of non-pollen plant parts as food sources for the common blossom thrips, Frankliniella schultzei

Like other flower thrips, Frankliniella schultzei Trybom (Thysanoptera: Thripidae) feeds on pollen. However, the influence of a pollen diet on the life history of F. schultzei may not be as significant as reported for other thrips species. Frankliniella schultzei was reared successfully and with low mortalities (20%) on Wax Mallow, (Malvaviscus arboreus Cav.) plant part diets. Development times and fecundity on a petal diet were not significantly different from that on a pollen diet. Fecundity on a diet combining M. arboreus pollen, petal and leaf tissues was significantly higher than those individually containing these tissues. In laboratory choice tests, F. schultzei females encountered petal most often of the three plant parts. Pollen and leaf were encountered with similar frequencies. A significantly higher proportion of petal encounters (0.8) resulted in feeding than did pollen encounters (0.5). Few leaf encounters (0.1) were followed by feeding. Adult and larval F. schultzei were found in M. arboreus flowers but not on leaves. All parts of the flower were inhabited and not just the pollen-bearing petal apices and anthers. We propose that feeding on pollen within M. arboreus flowers is just one of many influences on the life history of F. schultzei and suggest that this may extend to other thrips species/host-plant combinations.     

Feeding,Diet, and Jaw Form in West African Colobus and Procolobus

The functional link between mandibular morphology and masticatory stress has been documented by both experimental and comparative investigation. Somewhat more tenuous is the purported connection between dietary variation and the form of the jaws in primates. Several factors complicate the inference of such a connection, including anecdotal or incomplete dietary data from field studies and allometric effects on skeletal form that may have little to do with diet per se. We compared the jaws of sympatric colobines from West Africa to test the effect of diet on mandibular form. Procolobus badius and Colobus polykomos occupy the same habitat yet differ in diet primarily due to the exploitation of hard seeds by C. polykomos. The fact that the two taxa are comparable in body size also obviates the need for allometric qualifications. Colobus polykomos is expected to possess more robust mandibular corpora than Procolobus badius. In fact, the jaws of Colobus polykomos do not differ consistently from those of Procolobus badius in terms of biomechanical function. This apparent failure of mandibular morphology to reflect differences in diet and feeding behavior may be due to a variety of factors. We suspect that functional demands related to canine tooth support are contributing to obliteration of the expected biomechanical signal. Successful prediction of dietary effects on mandibular form requires consideration of competing structural and functional demands. The influence of diet on mandibular corporeal morphology is not equivalent across different primate species.     

Prickly coexistence or blunt competition? Opuntia refugia in an invaded rodent community

Endemic Nesoryzomys swarthi and invasive Rattus rattus exist in unlikely sympatry in Galápagos as female N. swarthi suffer from competition with R. rattus. This study evaluates the role of feeding habits in facilitating their co-occurrence. Spool-and-line tracking of 85 N. swarthi and 33 R. rattus was used to quantify their selected diets, foods of which were used in captive trials of 46 N. swarthi and 34 R. rattus to quantify their preferred diets. Selected diets were compared between species and seasons using niche measures, and contrasted to preferred diets to qualify inferences about competition. Diet overlap was highest in the wet season when food—particularly fruit—abundance was highest and R. rattus diet breadth was broadest. Preferred and selected diets were marginally correlated for R. rattus but uncorrelated for N. swarthi, suggesting that R. rattus interfere with N. swarthi foraging. Diet overlap was highest between female N. swarthi and R. rattus, perhaps due to female breeding requirements. Male N. swarthi avoided R. rattus-preferred foods, possibly to avoid aggressive encounters with R. rattus. During the dry season, when foods declined and the R. rattus population crashed, diet overlap was lowest as R. rattus diet narrowed in the absence of fruits. Female, and particularly male, N. swarthi diet broadened, with emphasis on acquiring Opuntia foods but N. swarthi-preferred and selected diets were uncorrelated, suggesting that their foraging was inhibited by R. rattus. In conclusion, the narrower diet breadth of R. rattus in contrast to N. swarthi suggests that this species may be less adapted to food acquisition at this site, particularly when fruits are absent. The year-round presence of R. rattus, however, appears to inhibit N. swarthi foraging for its preferred diet, and they instead specialise on Opuntia foods, which were uneaten by R. rattus and may provide N. swarthi with a localised competition refuge from encounters with R. rattus. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Similarities,differences, and seasonal patterns in the diets ofEulemur rubriventer andEulemur fulvus rufus in the Ranomafana National Park,Madagascar

I studied the diets of two sympatric species ofEulemur (E. fulvus rufus andE. rubriventer) in the Ranomafana National Part in southeastern Madagascar from July 1988 through August 1989. Both species were highly frugivorous throughout the year and devoted similar amounts of time to feeding daily; the composition of their diets were similar. Three aspects of both lemur species' diets were correlated with seasonal food availability: changes in interspecific dietary overlap, the length of feeding bouts, and the amount of time devoted to feeding daily. Throughout the year neither species had a more diverse or more folivorous diet than its sympatric congener. However, there were several consistent year-round differences between their diets.E. f. rufus initiated more feeding bouts daily that were shorter in duration than those ofE. rubriventer. E. f. rufus also consistently exploited more unripe fruits and mature leaves thanE. rubriventer did throughout the study.E. f. rufus migrated from the study site during a period of fruit scarcity. These dietary patterns are discussed here in regard to feeding patterns observed in other sympatric congeneric primate species, whether these dietary differences can contribute to these two species' ability to coexist, and how differences in diet may be influenced by differences in social structure. I suggest that subtle, consistent differences in diet and seasonal dietary differences are sufficient to allow these two species to coexist.     

Consumption of nematodes by fungivorous mites,Tyrophagus spp. (Acarina: Astigmata: Acaridae)

Summary Free-living nematodes may be attacked and eaten by soil mites which are normally considered fungivores or saprophages. Three species in the genus Tyrophagus, common inhabitants of grassland soils and also common pests in stored products, museums and laboratories, are predators of nematodes. All active stages of the mites will voraciously consume nematodes. When offered nematodes and a choice of other food (baker's yeast and algae), 11% of the Tyrophagus putrescentiae, 23% of the T. zachvatkini, and 56% of the T. similis tested fed on nematodes. Tyrophagus zechvatkini and similis were reared on a diet consisting entirely of nematodes, and developed at rates similar to a fungal diet and produced viable offspring. Agar cultures of Aphelenchus avenae which were inoculated with five mating pairs of Tyrophagus zachvatkini had populations that were one-third less than mite-free controls. Observations indicate that nematodes may be attacked by tyrophagid mites when in a dry, anhydrobiotic state.     

Host plant influence on chemical defense in conifer sawflies (Hymenoptera: Diprionidae)

Host diet affects the defensive efficacy of Neodiprion sawflies. In laboratory assays with wood ants (Formica obscuripes), secretions from larvae reared on Pinus banksiana were the most repellent, while those from P. resinosa feeders were the least so. This was explained diterpene resin acid content, but not total monoterpene content. The terpene content of regurgitant generally reflected dietary concentrations. Compounds were sequestered nonselectively by larvae. Host-based differences in defense persisted at the behavioral level. P. banksiana feeders regurgitated greater volumes of fluid and were less likely to be disabled or killed by ants in one-on-one interactions than were larvae fed on P. resinosa. The defensive advantages of host diet conflicted with developmental requirements. N. sertifer reared on P. banksiana (the best diet for defense in all cases) had lower cocoon weights (a correlate of fecundity) than those reared on other diets, and had prolonged larval development compared to insects fed P. sylvestris. No such tradeoff was detected in N. lecontei. Larvae of both species strongly preferred P. banksiana over P. resinosa in feeding choice assays.