摘要:

Abstract.1. The univoltine leaf‐mining moth, Lithocolletis quercus Ams., is endemic to Israel, where it spends its 10.5 month larval period feeding only in the leaves of Quercus calliprinos Webb.2. We compared patterns of egg deposition and sources of larval mortality to test whether oviposition patterns and site preferences confer an enhanced likelihood of larval survival.3. Dominant sources of larval mortality were premature leaf abscission and death from unknown causes, whereas predation, parasitism and intraspecific interference accounted for relatively little larval mortality.4. Eggs, and thus mines, were aggregated among leaves of host trees even though premature leaf abscission was positively correlated with density of mines per leaf. Interference competition among larvae was the only other density‐dependent mortality factor.5. Oviposition patterns within leaves mitigated the probability of death from larval interference, and probably also from early leaf abscission.6. Despite these density‐dependent mortality factors, overall probability of larval survival to pupation was independent of initial density of mines on a leaf.7. The long larval period allows synchrony between oviposition flights and times of predictable resource availab

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1989.tb00763.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Abstract.1. The tropical forest grasshopper Microtylopteryx hebardi Rehn (Orthoptera, Acrididae, Ommatolampinae) oviposits inside leaves or stems of its host plants. This is the first known instance of oviposition inside living plant tissue (rather than in the ground, on top of leaves, or in detritus) for a tropical forest acridid.2. In understorey secondary forest at La Selva, Costa Rica, M.hebardi females fed on fifteen species of host plants, but oviposited in only four of these.3. In laboratory choice tests, females showed selectivity for oviposition host plants similar to that inferred from field observations.4. Plant volume was a better predictor of the number of eggs laid per stem than variables that indicated leaf or stem characteristics of individual plants.5. Unlike the ovipositor of acridids laying eggs in the ground, that of M.hebardi is equipped with toothed, sclerotized edges, probably used to bore into plant tissue.6. Endophytic oviposition in M.hebardi may be related to finding host plants in a habitat that is complex, heterogeneous, and rich in plant species.

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1989.tb00764.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Abstract.1. The spring migration of the oriental armyworm moth, Mythimna separata (Walker), and other insects into northeastern China was observed by radar at a site in central Jilin province. Samples of the migrants were obtained in a net flown from a kite, and M.separata populations in the surrounding region were monitored with a trap network.2. The radar regularly detected echoes which were of the type characteristic of large insects, and three out of four large insects in the aerial samples were noctuid moths, including one M.separata. Catches of armyworm moths in the regional trap network peaked during the period of radar observations.3. Migration occurred at night. It commenced with a take‐off flight at dusk and generally continued until dawn, with numbers often being highest around midnight. Most migration took place at altitudes below 500 m, with strong layer concentrations forming at 200–400 m during the middle part of some nights.4. Migration was approximately downwind. The net movement was overwhelmingly to the northeast because southwesterly winds occurred most frequently and were relatively strong, and because migration was more intense and prolonged on these winds. Orientation tended to be to the left of the downwind direction, and was most often to the north or northeast.5. Migration into northeastern China was accomplished in a series of night‐time movements of 100–300 km rather than by a single non‐stop flight.6. The net movement of insects towards the northeast was sufficient to produce the observed regional infestation of M.separata moths. Oviposition by immigrant armyworm moths in vulnerable crops would have been at a level where economically significant damage would be expected from the resulting larval population.7. Analogous springtime migrations of noctuids leading to temporary colonizations of habitats at higher latitudes occur in other continents. Such colonizations may be unproductive if, as appears possibly the case for northeastern China, prevailing winds later in the season are generally unfavourable for a return migration towards overwintering areas at lower

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1989.tb00765.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Abstract.1. Parasitism of the bagworm, Thyridopteryx ephemeraeformis Haw. (Lepidoptera: Psychidae), on red cedar was studied at Manassas, Va., U.S.A.2. Fifteen parasitoids, five of which were hyperparasitoids, attacked the pupal stage of the bagworm. The Ichneumonid Itoplectis conquisitor alone accounted for 58% of the parasitized bagworms.3. Parasitism by I conquisitor (Say) was inversely related to host size, but independent of host distribution within a tree. Male bagworms experienced disproportionately higher levels of parasitism than females. We conclude that it is small size that renders bagworms susceptible to parasitism rather than sex per se.4. Ovipositor lengths of I.conquisitor were insufficient to penetrate the larger bagworm hosts (>57 mm); and in fact, as bagworm size increased, the proportion of the I.conquisitor population capable of penetrating the pupa declined abruptly. We suggest that the mechanical difficulties with oviposition, and perhaps the defensive capabilities of larger hosts, are responsible for the relationship between host size and per cent parasitism.5. I.conquisitor could be an important selective agent for bagworm size at pupation, but it is not likely to act as a significant control agent of population density.

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1989.tb00766.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Abstract.1. Assemblages of scale‐insects on deciduous fruit trees were compared in a wide geographic range of Palaearctic subregions.2. The parts of all host plant species in the whole geographic region were unsaturated with scale species. There was no clear niche expansion, nor any niche segregation between scale‐insect species.3. These results show that even plants such as deciduous trees, rich in coccoid species, are not fully utilized by scale insects.4. The similarity of the scale‐insect faunas on different plant species could be explained partly by the distribution patterns of the insects, and partly by phylogenetic connection between host p

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1989.tb00767.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Abstract.1. Female apple maggot (Rhagoletis pomonella Walsh) flies held in field cages usually oviposited in an unparasitized (non‐pheromone marked) fruit when it was encountered.2. Oviposition in a previously parasitized (pheromone marked) fruit depended upon the time since the last oviposition (TSLO) and the percentage of infested fruit encountered during search for oviposition sites.3. Previous theories of host acceptance suggest that the acceptance or rejection of a host should depend dichotomously on time since last oviposition and the fraction of marked hosts in the last five encounters. The experiments, however, show considerable variability and are thus not consistent with the theory.4. A new theory for the experiments is introduced. This model involves physiological (egg complement) and informational state variables and leads to intuitive understanding of the experimental results. In particular, the model shows how the plasticity in oviposition site selection may arise from fitness maximizing behaviour. Alternative models are also discussed. All of the models stress the importance of physiological and informational state

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1989.tb00768.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Abstract.1. The relationship between soil softness and nest initiation was studied at two aggregations of a ground nesting sphecid wasp, Cerceris antipodes Smith, in New South Wales, Australia.2. Nests of C.antipodes were initiated throughout the active season. Nests were started more frequently during moist conditions and when more wasps were active.3. Nest initiation was clumped on days after periods of rain. Nest initiation was only observed when the soil was soft.4. Two experimental plots that were watered had significantly softer soil and more nests initiated on them than two control plots. Searching female wasps spent considerably more time on the watered plots than the controls.5. Nest initiation through hard surface soils presents a problem to C.antipodes. Soil softness must be considered in any analysis of nest sharing in this species.

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1989.tb00769.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Abstract.1. The results of a recent faunistic survey of the Hymenoptera of northern Sulawesi, Indonesia, are compared with the known British fauna.2. All families of Hymenoptera are probably more species rich in Sulawesi than in Britain, with the possible exception of Symphyta and gall‐forming Cynipidae.3. The diversities of the samples obtained from Sulawesi are compared with those published from previous studies on the relationship between latitude, altitude and the diversity of parasitic Hymenoptera in tropical and temperate regions.4. Despite its possibly greater species richness, the Ichneumonidae as a whole was no more diverse in the Sulawesi samples than in samples taken in temperate areas, including Britain.5. The diversity of Parasitica as a whole appears to have been greater in the Sulawesi samples than those from either Britain or Michigan but lower than those from Costa Rica.6. Parasitica as a whole was probably not more diverse inside the forest than at its edge, but the Aculeata was more diverse at its edge.7. Both Parasitica and Aculeata were less diverse at 1765 m than at 220 m altitud

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1989.tb00770.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Abstract.1. Regulation of adult reproductive diapause and seasonal polyphenism was studied in two populations of the comma butterfly, Polygonia c‐album (L.) (Nymphalidae), from Stockholm, Sweden, and Oxford, England.2. In the univoltine Stockholm population short and long constant day‐lengths (in the range 12–22 h) at 20°C were ineffective in averting the production of the dark, generally diapausing, morph, but the non‐diapausing light morph could be produced if daylengths were increased during larval development. The procedure was especially effective with increases from 12 to 22 h, but the tendency was the same with a more realistic increase, from 18 to 20 h.3. In the partially bivoltine English population a critical constant day‐length for morph and diapause induction was found between 12 and 18 h. Decreasing daylengths above the critical daylength early or late in larval development resulted in production of the diapausing morph.4. These results suggest a system for environmental control where day‐lengths which increase throughout the larval period indicate an early date before summer solstice, meaning that there is sufficient time for a second generation of offspring to reach the hibernating adult stage before winter. The ecological significance of the results

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1989.tb00771.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Abstract.1. We report on the mating status of overwintering adults of the imported leaf beetle, Plagiodera versicolora Laicharting. This species overwinters as adults, under the bark of willow trees.2. Individuals were collected both in the autumn, just after initiation of diapause, and in the spring, just before natural termination of diapause. From the autumn sample, we discovered that diapause can be terminated by husbanding the adults at 4°C for 4 weeks.3. Most females lay fertile eggs upon the termination of diapause; however, a significant number of females lay non‐fertile eggs after overwintering in the field.4. Many females mate with more than one male before entering diapause. Progeny analysis using allozyme genetic markers shows that, on average, females who are fertile upon termination of diapause utilize sperm from 1.2 males to fertilize their eg

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1989.tb00772.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY