Effects of time-dependent intraspecific competition on offspring survival in the butterfly, Anthocharis scolymus (L.) (Lepidoptera: Pieridae)

Effects of mothers' eclosion and oviposition timing on the survival of their offspring in the pierid butterfly Anthocharis scolymus (L.) was examined. I recorded the performance of individual eggs and larvae that differed in their mother's eclosion and oviposition timing in a natural population, where A. scolymus feeds on Turritis glabra (L.) Bernh. Eggs laid early in the season, and larvae emerging from these eggs, had higher survival than eggs laid later, and larvae emerging from eggs that were laid later in the season, the causal factor being egg cannibalism by larvae on the same host plant. Logistic regression showed that females eclosing early in the season had higher offspring survival than females eclosing later. I conclude that optimal timing of adult eclosion in A. scolymus is a trade-off between eclosing early with associated higher offspring survival but lower egg-laying rate, and eclosing later with associated lower offspring survival but higher egg-laying rate. Received: 4 August 1997 / Accepted: 19 October 1997     

Distribution of early life history stages of fishes in selected pools of the Upper Mississippi River

Effective management of the fishery resources of the Upper Mississippi River and successful mitigation of the loss of critical habitat depend in part on an understanding of the reproductive and early life history requirements of the affected fishes. However, little is known about the use of nursery areas by fishes in the river. Of the nearly 130 species identified in the adult ichthyofauna, only a few are represented proportionally in the available data on early life stages because study designs have not included consideration of the early stages, collection gears have not adequately sampled the young, and eggs and larvae of some species are difficult to sample by conventional approaches. For the species collected, information is available on seasonal variations in total densities, composition, and catch among different habitat types. However, the data are most accurate for species with buoyant early life stages, such as freshwater drum (Aplodinotus grunniens) and gizzard shad (Dorosoma cepedianum). Eggs and larvae of freshwater drum dominate collections made in the main channel, whereas other larval fishes are usually most abundant in backwater habitats. The species found there usually deposit eggs on the substrate or on vegetation. Habitat preferences (as indicated by relative abundance) often shift as development proceeds and physical and behavioral changes occur in the larvae. Only limited information is available on the distribution of larvae within habitats, but it is clear that variations within habitats are significant.     

Comparative larval energetics of an ophiuroid and an echinoid echinoderm

The morphologically convergent larvae of the echinoderm classes Ophiuroidea and Echinoidea have been suggested to be functionally dissimilar when it comes to their capacities to feed, but little is known about whether these larvae are similar in terms of energetics. Here, we compare the energetics of early development of a tropical ophiuroid, Ophiocoma alexandri, and a temperate to tropical echinoid, Arbacia punctulata, two species with similarly sized eggs. Measurements of respiration and constituent analyses were performed on eggs and unfed larvae of both species. Members of both species showed an increase in oxygen consumption during morphogenesis followed by a lower, static rate once morphogenesis was complete (3 d for O. alexandri and 1.3 d for A. punctulata). Compared to the echinoid larvae, the ophiuroid larvae developed more slowly and had peak respiration rates that were 3.1× lower. Eggs of O. alexandri contained significantly more protein and significantly less triacylglycerol than eggs of A. punctulata. Energy utilization, as calculated via respiration measurements, closely matched decreases in energy content from the eggs to larvae as measured with biochemical constituent assays. Larvae of A. punctulata used 1.4× more energy to reach the pluteus stage than larvae of O. alexandri, and used 4× more energy during the first 9 d of larval life. These data suggest that echinoid larvae require more energy to develop to the feeding stage than ophiuroid larvae, and likewise have higher requirements for maintenance metabolism. Ophiuroid larvae may be more tolerant of low food levels due to their very low metabolic rates, but this advantage may be offset by their slower rate of development.     

Laboratory study of cannibalism and interspecific predation in ladybirds

Abstract.

• 1 In the absence of aphids, adult females of Adalia bipunctata (L.) showed a greater reluctance to eat eggs than males.
• 2 Eggs and young larvae were more vulnerable to cannibalism than older larvae and starved larvae were more vulnerable than well-fed larvae.
• 3 Both egg and larval cannibalism is inversely related to the abundance of aphids.
• 4 Eggs are a better food, in terms of larval growth and survival, than aphids.
• 5 In the absence of aphids interspecific predation occurred, but not equally, between the coccinellids A.bipunctata, A.decempunctata (L.), Coccinella septempunctata L. and C.undecempunctata L.
• 6 Larvae and adults of A. bipunctata and C.septempunctata were reluctant to eat conspecific eggs painted with a water extract of the other species' eggs and larvae of C. septempunctata were more likely to die after eating a few eggs of A.bipunctata than vice versa.
• 7 These results indicate that cannibalism occurs mainly when aphid prey is scarce and is adaptive in that it improves the chances of survival, and coccinellids, to varying degrees, are defended against interspecific predation.

     

Intraguild Predation among the Hoverfly Episyrphus balteatus de Geer (Diptera: Syrphidae) and Other Aphidophagous Predators

Aphidophagous predators compete for the same prey species. During their foraging activity they frequently encounter heterospecific aphid predators. These situations can lead to intraguild predation and may disrupt biological control efforts against aphids where more than one predator species is present. We investigated the behavior of larvae of the hoverfly Episyrphus balteatus de Geer and its interaction with three other aphid predators: the ladybird Coccinella septempunctata L., the lacewing Chrysoperla carnea Stephens, and the gall midge Aphidoletes aphidimyza (Rondani). Interspecific interactions between predators were examined in arenas of different sizes and in the presence of extraguild prey. The outcome of interactions between E. balteatus larvae and the other predators depended predominantly on the relative body size of the competitors. Relatively large individuals acted as intraguild predators, while relatively smaller individuals became intraguild prey. Eggs and first- as well as second-instar larvae of E. balteatus were highly susceptible to predation by all other predators, whereas pupae of E. balteatus were preyed upon only by the larvae of C. carnea. Interactions between A. aphidimyza and E. balteatus were asymmetric and always favored the latter. Eggs and first- as well as second-instar larvae of E. balteatus sustained intraguild predation irrespective of the size of the arena or the presence of extraguild prey. However, the frequency of predation on third-instar larvae of E. balteatus was significantly reduced. This study indicated that the same species can be both intraguild predator and intraguild prey. It is suggested that combinations of predators must be carefully chosen for success in biological control of aphids.     

Life history and population dynamics of Ectinohoplia rufipes (Coleoptera: Scarabaeidae) on Korean golf courses

Life history and temporal distribution of Ectinohoplia rufipes larvae (Coleoptera: Scarabaeidae; Melolonthinae) were studied on multiple courses at two Korean golf clubs in Gapyeong and Anseong, Gyeonggi Provinces. Larval density of E. rufipes was higher in roughs than fairways and higher on older courses than on newly constructed ones at each club. Larval density of E. rufipes in fall reached three to four times compared with the previous year in five or six year old courses in the first opened courses, but that took two or three years to reach three to four times in the newly constructed courses in the same golf club. Monthly sampling showed that larvae were distributed 3.0 to 5.8 cm beneath the soil surface; mean larval density ranged from 0.2 to 1.2/m² at each club. Most larvae overwintered as third instars that pupated in early May. Adults were first observed in late May at each course. Adults were first seen in emergence cages installed over a grub-infested portion of rough in early June. Eggs were deposited from late June to early July. Eggs hatched in mid to late July and larvae developed to become third instars by early October. Implications of these findings for managing E. rufipes on Korean golf courses are discussed.     

A new species of Acentrella Bengtsson (Ephemeroptera: Baetidae) from Great Smoky Mountains National Park,USA

Acentrella barbarae sp. n. is described from eggs, larvae, and imagines collected from Great Smoky Mountains National Park, North Carolina and Tennessee, USA. Larvae were collected from cobble-pebble substrate in stream rapids. Life stages were associated by rearing. Eggs have longitudinal chorionic ridges with small, longitudinal furrows. Larvae are distinguished by having segment 3 of the labial palp apically rounded, abdominal terga with posteromedian projections, and tibiae and tarsi with relatively short setae on the outer margins. Imagines are distinguished by the colouration and posterior elevation of abdominal terga. Other Acentrella larvae occur in the same streams as the new species, including A. parvula, which we report from Tennessee for the first time. We provide an updated key to the larvae of North American Acentrella species.     

Immature Stages of Tomapoderus(T.) ruficollis Fabricius (Coleoptera: Attelabidae) from Korea

Eggs, larvae and pupae of Tomapoderus (T.) ruficollis Fabricius are described and illustrated. The species is found on host plants, Zelkova serrata Makino and Ulmus davidiana var. japonica Nakai. and is a well‐known forest pest. Taxonomic notes and cradle structure of this species are provided.     

Evergreen foliage allows early hatching in a pine processionary moth and escape from predation

1. Seasonal variation in leaf quality and climate conditions often imposes constraints on the temporal occurrence of tree‐feeding insect larvae, but the seasonal effects of predation have received limited attention. In temperate climate zones, both the abundance and activity of predators can be expected to vary over time. 2. The study reported herein examined the impact of temporal variation in predator activity levels on the life history of an herbivorous insect feeding on a constant food source: previous‐year needles of Scots pine (Pinus sylvestris L.). In field experiments, the survival and growth rates of colonies of Thaumetopoea pinivora Treitschke larvae that had been manipulated to hatch at three different dates were compared. Eggs of T. pinivora usually hatch by mid‐April in southern Sweden, which is earlier than most other herbivorous insects that overwinter as eggs in this region. 3. Predator exclusion experiments indicated that larvae which hatched later than April experienced a higher level of predator activity, mainly by ants. The final larval size and the timing of pupation were not affected by hatching date. First instar larvae were more extensively preyed on than second instars. 4. The life history of herbivore species can be affected by seasonal variation in predation pressures. This study suggests that early hatching in a lepidopteran species can allow a temporal escape from predation during the vulnerable early life stages.     

Host-specificity of a root borer,Bembecia chrysidiformis [Lep.: Sesiidae], a potential control agent forRumex spp. [Polygonaceae] in Australia

Bembecia chrysidiformis (Esper) [Lep.: Sesiidae] was examined for its natural history and specificity toRumex spp. (Polygonaceae) which are weeds in Australia. Adults of this southern European insect appear in late spring to summer. Eggs are laid on the dried, seed bearing stems of perennialRumex plants. The larvae tunnel inside the root during summer through to the next spring. In nature, the larvae are round inRumex species of the subgeneraRumex andAcetosa. In host-specificity tests with 1st instar larvae, the roots of a number of genera within thePolygonaceae were attacked. Larvae died on a range of plants from other families except inPersea americana Miller(Lauraceae), Helianthemum nummularium (L.) Miller (Cistaceae) andQuercus ilex L. (Fagaceae) where larvae fed on the stems. The insect was judged safe for release in Australia by assessing aspects of its biology, its known host plants, and the lack of reported attack on other plants.      

Evaluation of an improved method for mass-rearing of thrips and a thrips parasitoid

Improved laboratory methods are described in detail for mass rearing of various thrips species, such as Frankliniella occidentalis, Frankliniella intonsa, Thrips palmi, Thrips tabaci (Thysanoptera: Thripidae) and a thrips parasitoid, Ceranisus menes (Hymenoptera: Eulophidae), using various foods. In one method, plant pollen and honey solution are used as food sources. In a second method, germinated broad bean seeds are used. Eggs, produced in large numbers in water, are collected by a suction funnel onto a filter paper and incubated in a Petri dish. Large numbers of larvae that hatch are collected by using food traps (plant pollen). Larvae can be reared on pollen or on germinated broad bean seeds until adult emergence without additional water and food. This method has been found useful for producing even-aged thrips at different densities (up to 500 larvae in a cage of 80 mm diameter) with relatively low mortality rates. Evaluation of this rearing method for F. intonsa, shows that during 2 weeks at 20 °C per 100 females more than 4000 females could be produced in the next generation. About 5 min per day is required to achieve this productivity of mass production. The method is also suitable for producing large numbers of the solitary endoparasitoid of thrips larvae, C. menes.     

Specificity of an ant-lycaenid interaction

Summary Many lycaenid butterflies are believed to be mutualists of ants — the butterfly larvae secrete sugars and amino acids as rewards for the ants, and the ants protect the larvae from predation or parasitism. We examined the specificity of the relationship between the lycaenid Plebejus argus and ants in the genus Lasius. Eggs were not attractive to Lasius ants until the emerging larvae had broken through the chorion. First instar larvae were palpated and picked up by Lasius workers and taken to the nest. First instars were mostly ignored by Myrmica sabuleti ants and they were rarely detected by Formica fusca. Older larvae were more attractive to Lasius than to the other ant genera. Pupae were very attractive to Lasius, moderately so to Myrmica, and were ignored by Formica fusca. Teneral adults were palpated by Lasius, but were attacked by Myrmica and Formica workers. We conclude that P. argus is a specialist associate of Lasius ants. Two populations of Plebejus argus were compared: one is naturally associated with Lasius niger, and the other with Lasius alienus. In reciprocal trials, larvae were slightly more attractive to their natural host ant species. Since test larvae were reared on a single host plant species in captivity, this differentiation probably has a genetic basis.     

Developmental morphology of the cottid fish Pseudoblennius marmoratus

Embryonic, larval, and juvenile development of a Japanese cottid fish Pseudoblennius marmoratus is described from laboratory-reared specimens. Eggs of P. marmoratus resembled those of two congeners, Pseudoblennius cottoides and Pseudoblennius percoides, but differed in their smaller diameter and yolk color. Although the larvae and juveniles of P. marmoratus were also similar to them in general morphology, the former differed in the lengths of newly hatched larvae, pigmentation patterns, number of pectoral fin rays, and dorsal fin spine elongation.     

A new method for the production of sterile colonies of Lucilia sericata

Maggot debridement therapy (MDT) refers to the use of blowfly larvae to clean or debride an infected wound. Most commonly, larvae of Lucilia sericata (Meigen) (Diptera: Calliphoridae) are used, and are sterilized prior to use to ensure no further bacterial infections are introduced during treatment. Current methods sterilize eggs from laboratory‐reared blowfly colonies, after which sterile early second instar maggots can be provided to hospitals for use in treatment. Maggots not required for treatment are used for colony regeneration, in which sterility is not maintained. The ability to maintain sterility beyond this would allow further research into fly–bacteria interactions and the effects of different bacteria on the blowfly lifecycle. This study aimed to produce a colony of sterile adults, using current egg sterilization practice, but maintaining sterility through to pupation and emergence. The production of a sterile colony allows further research into the impact of bacteria on fly development and survival. Eggs were placed on a sterile food source within autoclaved plant tissue culture containers to allow growth under sterile conditions. Nutrient agar plating of sterilized and non‐sterilized eggs, larvae and adults (post‐emergence), as well as the pupation medium and feed source in nutrient broth confirmed the aerobic sterility of all samples involved. The lifecycle of L. sericata was successfully completed through pupation to emergence with no effects on lifespan or oviposition by the newly emerged, sterile adult colony.     

Biology of Lilioceris spp. (Coleoptera: Chrysomelidae) and their parasitoids in Europe

The biology and parasitoid complex of the lily leaf beetle (LLB), Lilioceris lilii Scopoli, and two congeneric species were investigated in Europe, as part of a biological control program against the LLB in North America. Eggs, larvae, and adults of L. lilii were collected in several countries in Europe, on both cultivated and wild Lilium spp., and reared in the laboratory and under natural conditions. Parasitoids were obtained and their biologies were studied. Similar investigations were made in Switzerland on two closely related species Lilioceris tibialis (Villa) found on wild Lilium spp., and Lilioceris merdigera (L.) on several other Liliaceae. The three species are strictly univoltine. Adults overwinter and lay eggs on leaves in early spring. The three beetle species have four instars, which were characterized by their head capsule width. Pupation occurs in a cocoon in the soil. Adults emerge in late summer and start feeding before reaching overwintering sites. Egg and larval parasitoids were obtained. Eggs of L. lilii and L. merdigera were parasitized by the mymarid Anaphes sp., a multivoltine species that needs alternate hosts for overwintering. Larvae were heavily attacked by several parasitoids, among which the most abundant were three ichneumonids, Lemophagus pulcher (Szepligeti), L. errabundus (Gravenhorst), and Diaparsis jucunda (Holmgren), and the eulophid Tetrastichus setifer Thomson. All four parasitoid species were found in the three beetles and in most European regions, but strong variations were observed in their relative abundance among hosts and geographic regions. Three of the four main larval parasitoids are strictly univoltine, whereas L. pulcher has a partial second generation. Lemophagus spp. are frequently parasitized by the ichneumonid hyperparasitoid Mesochorus lilioceriphilus Schwenke. Further details of the biology of the parasitoids are described, and their potential as biological control agents is discussed.     

Biparental mouthbrooding and guarding in a Tanganyikan CichlidHaplotaxodon microlepis

Differences between parental roles of males and females inHaplotaxodon microlepis (Cichlidae) were investigated in Lake Tanganyika, and the early ontogeny and growth of the species were studied in the aquarium. Eggs were mouthbrooded by the female, and it is suggested that small larvae (<9 mm in total length) were also mouthbrooded by females though such samples were not collected. Above this size the larvae began to feed, and parents jointly performed mouthbrooding and guarding until the young grew to 25–30 mm, nearly 2 months after spawning. Males and females mouthbrooded to the same extent, but when a part of the brood was released, females mainly guarded the released brood and males took the mouthbrooding role. Differences in parentalcare patterns betweenH. microlepis and other monogamous mouthbrooding cichlids are discussed.     

Morphology and development of <Emphasis Type="Italic">Pteromalus cerealellae</Emphasis> (Ashmead) (Hymenoptera: Pteromalidae) on <Emphasis Type="Italic">Callosobruchus maculatus</Emphasis> (F.) (Coleoptera: Chrysomelidae)

Pteromalus cerealellae (Ashmead) (Hymenoptera: Pteromalidae) is an ectoparasitoid of several stored-product insect pests. Very little information has been published on its biology and development in host larvae, which typically are concealed within seeds. We documented the development of P. cerealellae within fourth instar larvae of its concealed host, Callosobruchus maculatus (F.) (Coleoptera: Chrysomelidae) infesting cowpea seeds. The preimaginal life stages of the parasitoid were characterized for the first time using morphological structures revealed by microscopic techniques including scanning electron microscopy. Pteromalus cerealellae produces hymenopteriform eggs and larvae. Eggs hatch into 13-segmented first instar larvae with peripneustic condition of spiracles. The larvae have simple, tusk-like mandibles, whereas the mandibles of the pupae and the adults are of the conventional toothed types. Using statistical analyses of the sizes of the larval mandibles and head capsules in conjunction with reliable characters such as the number of exuviae on the body of parasitoid larvae, cuticular folding, and excretion of the meconium, we recorded four larval instars for P. cerealellae. The data showed significant positive correlations between larval mandible lengths and widths of larval head capsules, as well as between mandible lengths and larval instars, suggesting that mandible length is a good predictor of the number of instars in P. cerealellae. Developmental time from egg to adult emergence was ∼12 d for females and ∼11 days for males at 30 ± 1°C, 70 ± 5% r.h. and 12L:12D photoperiod.     

Biology of Larinus curtus Hochhut (Coleoptera: Curculionidae), a European Weevil for Biological Control of Yellow Starthistle Centaurea solstitialis L (Asteraceae), in the United States

The biology of the weevil Larinus curtus Hochhut was studied in the field in northern Greece and in the laboratory in Rome, Italy, and in Thermi, near Thessaloniki, Greece. The species is univoltine, and adults overwinter in ground litter. Eggs are inserted into the flowers of yellow starthistle (Centaurea solstitialis L.) where the larvae feed mainly on developing achenes, destroying on average over 96% of the seeds in infested flowerheads. Overwintered adults lived up to 84 days, females laid up to 70 eggs each, eggs hatched 4.2 ± 0.6 days after being laid, larvae required 17 to 20 days to develop through the four instars, and pupal development required 4 to 5 days under laboratory conditions. Six percent of 360 seedheads collected on July 13 and 28, 1988 were infested with L. curtus larvae and up to 89% of the larvae were parasitized. The species is recommended for the biological control of C. solstitialis in the United States.     

A preliminary note on the intestinal parasites of wild chimpanzees in the Mahale Mountains,Tanzania

Feces of wild chimpanzees in the Mahale Mountains, Tanzania, were inspected for intestinal parasites under a compound microscope. Eggs or larvae ofOesophagostomum, Strongyloides, Trichuris, Prosthenorchis, andBertiella were found. Intestinal nematodes significantly increased in the mid-rainy season. This finding supports (or, at least, is not in conflict with) the hypothesis thatAspilia leaves which are occasionally swallowed by chimpanzees may function as a vermicide, since ingestion of such leaves also increases significantly in the mid-rainy season.     

Lasioseius Fimetorum: a soil-dwelling predator of glasshouse pests?

Female lifespan and reproduction, in terms of numberof larvae produced, of the soil-dwelling predatorymite Lasioseius fimetorum Karg (Acari:Podocinidae) fed on mould mites (Tyrophagusputrescentiae [Schrank] [Acarina: Acaridae]) wereinvestigated by laboratory experiments at 20 °C,as were the mite's consumption rates of various prey.After a preoviposition period of 10.7 days, L.fimetorum produced progeny at a daily rate of 0.7.The oviposition period lasted 23.6 days and a total of19.4 progeny were produced per female. Females livedfor 38.6 days. Eggs of the Collembola Isotomurusspp. (Collembola: Isotomidae) were consumed in thelargest amount by L. fimetorum followed by mouldmite nymphs, larvae and pupae of thrips (Frankliniella occidentalis [Pergande] [Thysanoptera:Thripidae]), eggs of the Collembola Micrisotomaspp. (Collembola: Isotomidae), Isotomurus spp.nymphs and sciarid larvae (Bradysia pauperaTuomikoski and B. tritici (Coquillet) [Diptera:Sciaridae]). Immature drain flies (Psychoda spp.[Diptera: Psychodidae]) were not consumed by L.fimetorum. The suitability of L. fimetorum forbiological control of glasshouse pests withsoil-dwelling stages is discussed in comparison withanother predatory mite Hypoaspis miles Berlese(Acarina: Hypoaspididae).