摘要:

Abstract.1. The effect of increasing concentrations of an iridoid glycoside, catalposide, was tested on a generalist and an adapted specialist lepidopteran, using artificial diets.2. Two strains of the gypsy moth, Lymantria dispar (L.) (Lymantriidae), were tested. Larvae of a wild strain showed a negative dose‐dependent response to increasing concentrations of catalposide (up to 7.2% dry weight), while a laboratory strain showed no such pattern. Choice tests using the laboratory strain showed that these larvae often preferred diets relatively low in catalposide over those with higher concentrations.3. In contrast, larvae of the iridoid glycoside specialist, the buckeye, Junonia coenia Hübner (Nymphalidae), showed a positive dose‐dependent response and grew better on diets with higher doses of catalposide.4. We tested whether the improved growth of J. coenia at higher concentrations of catalposide may have been due to extra glucose yielded by hydrolysis of catalposide. Larvae were fed increasing doses of glucose equivalent to the amount potentially obtained by hydrolysing the quantities of catalposide used in the previous experiment. However, added glucose did not effect growth, suggesting that increased growth at higher catalposide concentrations was due to increased feeding r

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1989.tb00953.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Abstract.1. The searching behaviour of the parasitoid Sympiesis sericeicornis Nees (Hymenoptera, Eulophidae) is analysed under field conditions.2. Females were tracked when flying around the canopy of apple trees infested with the tentiform leafminer Phyllonorycter cydoniella (D.&S.)(Lepidoptera, Gracillariidae) and their behaviour studied at the level of a single mine and at the level of several mines on the same leaf (patch level).3. The presence of mines is detected during flight. The foraging behaviour at the patch level is efficient: the female is able to distinguish the suitable from the unsuitable hosts and handle the suitable hosts first. Not all mines are visited before departure from the leaf and those left unvisited are exclusively mines without suitable hosts. The patch leaving rule is discussed.4. An ethogram of the behaviour on the mine is constructed. Selected behavioural categories are analysed for different combinations of mine content and outcome of the visit to the mine. The assessment of the mine content is done in a differential way, quickly and without mistakes.5. The results are discussed in the context of two environmental factors, wind speed and temperature, which reduce the available time for searching. They are also related to the growing percentage of unsuitable hosts during each host generation. Tentiform mines remain attractive for a long period of time, even after parasitism or emergence of the adult, and their examination reduces the rate of host discovery.

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1989.tb00954.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1989.tb00955.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Abstract.1. The pedunculate oak, Quercus robur L., suffers high annual levels of spring defoliation in Wytham Woods, Oxon. The two major defoliators, Tortrix viridana L. and Operophtera brumata L., sometimes reach high enough densities to completely defoliate trees.2. Experiments with larvae of both species enclosed on oak trees in Wytham Woods suggest considerable potential for intra‐ and interspecific competition between T. viridana and O. brumata.3. T. viridana and O. brumata consume equivalent amounts of leaf tissue per unit caterpillar density. Despite this, O. brumata is the superior competitor, measured by mortality during the larval feeding period.4. Evidence is presented that T. viridana larvae depend upon the protected microclimate of leaf rolls to maintain water balance, and that leaf damage may disrupt the construction of, and microclimate within, leaf rolls. O. brumata may therefore be competitively superior because it indirectly interferes with the water balance of T. viridana.5. The importance of interspecific competition in the dynamics of T. viridana and O. brumata populations is discussed. Stochastic mortality factors acting on first instar larvae of both species probably make intense competition a rare even

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1989.tb00956.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1989.tb00957.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Abstract.1. In a 3‐year study of the solitary bee Colletes cunicularius L. in Sweden, average body size and population density fluctuated greatly between years.2. In this protandrous population, females mated just once and the sex ratio was slightly male biased. Males were smaller than females.3. Size assortative mating (homogamy), associated with an increase in population density during the central days of female emergence and mating, was observed in two out of three years. Homogamy was also observed in pairs with remating males.4. Most of the mating males had emerged the day they mated, but 42% were older. We found no support for a general large‐male mating advantage.5. Weight of emerging females and mating males were negatively correlated with ground temperature, indicating thermoregulatory influence on the process of sexual selection in this spec

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1989.tb00958.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Abstract.1. The larvae of four swallowtail butterfly species, Papilio polyxenes Fabr. in the Papilionini, Parides bunichus (Hübner) and Battus polydamas (L.) in the Troidini, and Eurytides marcellus (Cramer) in the Graphiini, were grown on host leaves to which test compounds had been added.2. The test chemicals are biosynthetically related. Berberine, a 1‐benzyl‐tetrahydroisoquinoline‐related (1‐BTIQ) alkaloid, is found in many rutaceous hosts of the Papilionini; laudanosine, a simpler 1‐BTIQ alkaloid, is found in the Papaveraceae, plants on which no papilionids feed; aristolochic acids are found only in the Aristolochiaceae, hosts of the Troidini.3. Swallowtail larvae can tolerate the compounds characteristic of their host plants, but not chemicals found in the hosts of other papilionid groups. Diets with laudanosine did not affect the test species.4. Our results support the contention that plant secondary chemicals, such as berberine and aristolochic acids, are important feeding barriers, and are partially responsible for host specificity in sw

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1989.tb00959.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Abstract.1. Variation in size (wing length) of females and males within a population of Aedes punctor (Kirby) at emergence was recorded in northern Britain during 1984 and 1985.2. Wing length correlated well with body dry weight, confirming its usefulness as a measure of body size. In 1984, but not in 1985, mean size decreased significantly as emergence progressed.3. The size of host‐seeking females caught at human bait varied seasonally. This was partly accounted for by size variation during emergence.4. Of females which fed to repletion, the largest spent least time in contact with the host.5. In the laboratory, wing length correlated well with potential fecundity (number of ovarioles) and less well with actual fecundity (number of matured follicles) after feeding on human blood.6. In the field, larger females were more successful at locating hosts, developed more egg clutches in a lifetime and generally lived longer than did smaller ones. Larger females appear to enjoy greater reproductive success than do smaller female

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1989.tb00960.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Abstract.1. Onset and spread of the severe outbreaks of African armyworm, Spodoptera exempta (Walk.), over Ethiopa, Kenya, Tanzania and Burundi in late 1984 have been analysed in relation to trap and weather records.2. Although first outbreaks in each country appeared progressively further south, winds on the best estimated dates of moth concentration and egg laying blew from directions precluding moth movements between them.3. Such independently developing outbreaks are called ‘primary’ to distinguish them from any ‘secondary’ outbreaks that may develop from them.4. Parent moths giving rise to all seven areas of primary outbreaks were derived from low‐density populations that had persisted through the dry season, probably near the coast of East Africa.5. Primary outbreaks developed on the south‐eastern sides of individual rainstorms over the highlands, most likely because windborne moths were concentrated there by convergent winds.6. Of the secondary outbreaks within Kenya, Tanzania and Burundi, most were derived from only one area of primary outbreaks in Kenya, which were therefore critical for effective control of spread; the paucity of other secondaries was presumably due to a lack of timely rainstorms or other concentrating

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1989.tb00961.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Abstract.1. In the three caddis fly species, Athripsodes albifrons (L.), A. cinereus (Curtis) and Mystacides azurea (L.) (Leptoceridae; Trichoptera), males swarm above the water surface of lakes or rivers. Receptive females fly to swarms and are chased and/or courted by males. After one of the swarming males has grasped an approaching female, the pair flies in tandem to the shore where they copulate.2. In males, wing wear indices were negatively correlated with the ratio of fat/dry weight. In the only species in which comparisons were possible between newly emerged and swarming males (M. azurea), the former had significantly lower indices. Unmated females on average had lower wing wear indices than spent females. These facts suggest that wing wear reflects relative age.3. The tandem males had significantly less wing wear than those in swarms, and are probably therefore younger. Age is therefore likely to be significant in relation to mating success.4. Among males of the same relative age, tandem males had higher fat ratio than swarming ones, indicating that male mating success was also influenced by traits other than age. It is suggested that the shortest possible duration of the period of adult prematurity is adaptive, especially in insects with marginal adult food intake.

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1989.tb00962.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY