The adaptive significance of leaf-mining pattern as an anti-parasitoid strategy: A theoretical study

An adaptive significance of linear leaf mining patterns as the anti-parasitoid strategy is theoretically analysed. In the model, a leaf-miner is allowed to move in one of four ways; mining ahead in unexploited area of a leaf, backtracking, branching off from the backtracking mine, and crossing the previous mine. The model parasitoid searches for the leaf-miner by tracing the mine by the tactile cue of mine surface after detecting the mine. The average duration from detecting the mine to finding the leaf-miner host is calculated for various patterns of mining, changing numbers of branches and of crosses. This average duration becomes longer when the leaf-miner stays near either end of the mine compared with when staying near its center. It is also prolonged as the numbers of branches and of crosses increase.     

Economy of food utilization in a gregarious sawfly,Arge nigrinodosa Motschulsky (Hymenoptera: Argidae): Relative abundance of food in the natural habitat and behavioral pattern of larval feeding

Summary Relative abundance of natural food resource, leaves of wild rose, ofArge migrinodosa was evaluated by comparing the food quantity which the larvae composing a colony utilized throughout the larval stage with that which is available in the habitat. In this connection, behavioral pattern of larval feeding was also observed under natural conditions, and its ecological significance was discussed. It was quantitatively clarified that the larvae faced the severe shortage of food and had to disperse to other shoots with the expense of probably high risk. Under pressures of such insufficient supply of food, the larvae follow the most efficient pattern of feeding behavior that they move to the tip of shoot at first and feed regularly downward thereafter. Though individual larvae behaved completely independently of each other, the aggregation appeared to be formed and maintained because all the larvae from the same egg mass follow this fixed feeding pattern.     

Effect of organic amendments on the growth and chemical composition of tomato,eggplant and chilli and their susceptibility to attack byMeloidogyne incognita

Summary Fewer larvae ofMeloidogyne incognita invaded and fewer galls were formed when seedlings of nonresistant varieties of tomato, eggplant and chilli were growing in soil to which oilcakes of mahua, castor, neem/margosa, mustard and groundnut had been added. Chemical analysis of plant tissue showed that, compared with untreated plants, plants growing in treated soil contained greater concentrations of phenols and frequently of amino acids, proteins and carbohydrates.     

Habitat stability and the larval mosquito community in treeholes and other containers on a temperate Island

The temporal fluctuation of water levels and the presence of mosquito larvae were investigated for four types of small container habitats (treeholes, bamboo stumps, cemetery stone vases, and cemetery stone vessels) on Kabeshima Island in Kyushu, southwestern Japan. The probability that containers held water was positively correlated with the quantity of the preceding rainfall and with the depth and volume of the containers. It was estimated that dehydration occurred more regularly in autumn and winter than in summer. The probability that mosquito larvae were present in each type of container was positively correlated with habitat stability in terms of the probability of the existence of standing water and the coefficient of variation of the water level. Twelve species of mosquito larvae, including two rare predators, were found. Species composition differed between the different types of container. Although 4 to 10 species used each type of container, the median number of species per container was two for treeholes and bamboo stumps, and one for the others. The dominant species wasTripteroides bambusa in treeholes and bamboo stumps,Aedes albopictus in stone vases, andA. japonicus in stone vessels. The larval mosquito community, which lacked major predators, possessed the following features that may facilitate the coexistence of many species: (1) niche segregation amongst species in terms of their selection of container types; (2) an aggregated distribution of the individual species among containers of the same type; (3) high intraspecific mean crowding (and hence probably intense intraspecific competition) in the dominant species in each type of container; (4) independent species associations within the same type of container; and (5) low interspecific mean crowding (and hence probablynot intense interspecific competition) between species in the same type of container.     

Trends in the recovery of a rosy marsh moth Coenophila subrosea (Lepidoptera, Noctuidae) population in response to fire and conservation management on a lowland raised mire

Following a severe fire in 1986 on the estuarine raised mire of Cors Fochno, Wales, a larval transect was initiated across the burnt and unburnt sections to investigate the recovery of the rosy marsh moth Coenophila subrosea population. This paper reports the results of 16 years of surveillance and relates larval density to the growth of the main food plant, bog myrtle Myrica gale. Earlier suggestions that fire is a necessary management tool to maintain Myrica at a young stage of its growth appear unfounded and hydrological effects are probably sufficient to ensure rapid turnover of the foodplant. Eighteen years in which there has been no significant disturbance to the mire vegetation has not led to the predicted decline in the moth population. However, changes in vegetational composition are occurring as a result of conservation management to the hydrological regime of the mire and further studies will be required to investigate whether restoration of the peatland water table leads to a significant reduction in the abundance in food plants or a decline in the status of the rosy marsh moth.     

The estimation and simulation of variable developmental period,with application to the mosquitoAedes aegypti (L.)

The variability of stage developmental period may be a seminal feature of some insect populations and therefore of importance in management studies. A transfer function technique is described for estimating the frequency distribution of developmental period and simulating the subsequent population dynamics. The technique relates recruitment time series of consecutive stages by an age-specific developmental success function. Approximate statistics, such as the mean, median or mode developmental period, may be determined and the effect of different temperature or density regimes compared.     

Implications of feeding specialization on the recruitment processes and community structure of butterflyfishes

Synopsis When settling on coral reefs, fish larvae generally change from zooplanktivory to diverse forms of benthic feeding. Whereas food has not been reported to directly influence settlement, it is hypothesized that food resource might play a major role in the recruitment processes of butterflyfishes. Benthic feeding was found to occur immediatly after settlement, and was related to the degree of specialization of adult diets. Among obligate coral feeders scleractinian polyps were the exclusive diet of new recruits. In non-obligate corallivorous chaetodontids tentacles of sedentarian polychaetes were the preferred prey of juveniles for all the species studied, and represented on average 36.2% of their prey by weight. They formed a transitional food resource for these species which mainly fed on scleratinian polyps when adults (51.6% by weight). Among the chaetodontids studies, some recruited within adult home sites, whereas others exhibited size-specific distributions. The different patterns observed were not closely related to food specialization of the adults. The importance of food resources to the community structure of butterflyfishes on coral reefs is discussed.     

SMURFs: standard monitoring units for the recruitment of temperate reef fishes

I evaluated a standard monitoring unit for the recruitment of reef fishes (SMURF) as a tool for ascertaining spatial and temporal patterns of reef fish recruitment in central California, USA. SMURFs consisted of a 1.0×0.35 m dia. cylinder of fine mesh plastic grid that contained a folded section of larger mesh plastic grid. SMURFs collected new recruits of 20 species of fish with 92% of the individuals collected from 10 species, mostly rockfish (genus Sebastes). An experiment varying depth of SMURFs in the water column (surface, mid-depth, or bottom) showed that surface SMURFs collected the greatest diversity of species and significantly greater abundance for eight species, with two species having significantly greater abundance on mid-depth SMURFs and three species having significantly greater abundance on bottom SMURFs. A comparison of cumulated recruitment from SMURFs that varied in sampling frequency (removal of new recruits every 1-3, 7, or 28 days) suggested that increasing the time between sampling caused a significant decrease in recruitment estimates for some species but not for others. To determine how well temporal patterns of recruitment to SMURFs reflected patterns to nearby reefs, I compared within season temporal patterns of recruitment to SMURFs with that at nearby reefs, estimated by visual transect surveys conducted on scuba. Temporal patterns of recruitment to SMURFs were significantly and positively related to early recruitment on reefs for one group of benthic-algal associated rockfish species when diver surveys were lagged by 30 days (r=0.87) and for another group of canopy-algal associated rockfish species when lagged by 5 days (r=0.72). SMURFs appeared to be an effective and efficient method for indexing relative rates of delivery of competent juveniles for many temperate nearshore reef fishes.