The influence of cucumber offered as a host plant either alone or with Aphis gossypii Glover (Hemiptera: Aphididae) was studied on the various life table and biological characteristics of the predatory bug Macrolophus pygmaeus Rambur (Hemiptera: Miridae). The nymphal development was studied at 15, 20, 25, 30 and 35°C while adult performance was assessed at 15, 20, 25 and 30°C, using a 16L : 8D photoperiod and 65 ± 5% r.h. Nymphs completed their development at all temperatures except at 35°C. Nymphal development took significantly longer time in the absence than in the presence of prey at 20 and 25°C, but the reverse was true at 15°C. Nymphal mortality was highest at 15°C in the presence of prey and it was mainly recorded at the first and second stages. Females oviposited a small number of eggs at all temperatures but not at 30°C in the absence of prey. The average number of eggs per female was almost similar with or without prey, being highest at 20°C, and adult longevity was highest at 15°C. The results concerning population parameters clearly showed that cucumber with or without prey can not support a population increase of M. pygmaeus. However, it seems that A. gossypii on cucumber inhibits development of M. pygmaeus more than when this aphid species is not present. This adverse effect on this host plant-prey system possibly results from the particular aphid genotype on cucumber, leading to high nymphal mortality, reduced fecundity and short adult life-span of M. pygmaeus.
We investigated the ability of females of the aphidophagous chrysopids Chrysopa oculata and Chrysopa perla to distinguish clean substrates from substrates with tracks of chrysopid first instars after ablation of various sensory organs potentially involved in the detection of oviposition-deterring semiochemicals (ODSCs). Also studied were effects of storage time on the degree of oviposition deterrence of substrates contaminated by larvae and by extracts of ODSC in intact females. C. oculata and C. perla laid significantly fewer eggs on substrates with conspecific larval tracks than on simultaneously provided clean substrates. Females of both chrysopids could perceive ODSCs solely through sense organs on the head. The oviposition of each species was significantly lower on contaminated than on clean substrates when any kind of sense organ on the head was completely removed, i.e. antennae, maxillary palpi, or labial palpi. C. oculata could still effectively differentiate substrates after ablation of both maxillary and labial palpi, indicating possible detection of volatiles via the antennae during flight. Only if all three pairs of sensory appendages were removed did females lay similar numbers of eggs on both substrates. In contrast, C. perla laid similar numbers of eggs on clean substrates and substrates with either conspecific or C. oculata larval tracks when maxillary and labial palpi were removed. Substrates with tracks of first instars of C. perla deterred C. oculata from oviposition after one year and conspecific females after 1.5 years from contamination. Both species laid significantly fewer eggs on substrates with tracks of C. oculata first instars than on clean substrates even after three years. Tracks of C. oculata third instars did not deter conspecific females more than tracks of first instars. ODSCs from tracks were easily extracted with water. Thus, precipitation is likely to reduce deterrent effects of contaminated plants. Chloroform extract from C. oculata first instars strongly deterred conspecific females from oviposition. Even after 725 days of storage, we found no statistically significant decline in the effect. The extract could be used to redirect egg laying from constructional parts of rearing cages to exchangeable oviposition substrates in mass rearing of chrysopids used for biological control. The hexane extract of third instars was inactive.
This paper examines some biological aspects and the predatory capacity of Chrysoperla externa fed nymphs of Sipha flava and reared at different temperatures. Recently hatched larvae were placed individually in Petri dishes, fed ad libitum with S. flava and reared at either 12, 16, 20, 24, 28 or 32 ± 1°C, a RH of 70 ± 10% and a 12-h photophase. The experiment was fully randomized with 30 replicates of each treatment. The duration and survival in each instar, and larval and pupal stages (pre-pupa + pupa) were analyzed. To determine the predatory capacity of larvae they were each provided daily with three-day-old nymphs of the aphid, in a number greater than they could consume. Ninety C. externa larvae were kept individually in Petri dishes at 24 ± 1°C, and their daily consumption recorded during development. Temperature influenced the rate of larval and pupal development. There was a decrease in the duration of development with increase in temperature. Regression analyses, based on quadratic equations, were used to describe the effect of temperature on the duration of development in the different instars of C. externa. This revealed that the base temperature increased as the larvae developed towards the adult phase. The survival of larvae in the first and second instars was similar at 12, 16, 20, 24, 28 and 32°C but none of the third instar larvae completed their development at 12°C and 32°C. The average daily and total consumption of aphids by third instar larvae was about 48 times greater than that of first instar larvae. The larvae ate an average of 10, 37 and 479 aphids in the first, second and third instars, respectively.
The semiochemical relationships in a predator-prey-host plant system were studied by a series of multiple-choice field assays. The studied system included predatory flies of the genus Medetera (Diptera: Dolichopodidae), the bark beetles Ips typographus and Pityogenes chalcographus (Coleoptera: Curculionidae: Scolytinae) as prey and Norwegian spruce (Picea abies) as the host plant. Of the nine species of predators collected, only M. setiventris and M. melancholica provided sufficient data for statistical analysis. The response of the predators to monoterpenic products of the host (alpha-pinene, limonene, camphor), pheromone compounds of I. typographus (S-cis-verbenol and 2-methyl-3-buten-2-ol) and a mixture of the pheromones of I. typographus and P. chalcographus were investigated. Our field trials revealed that tree volatiles plus pheromones of the prey, and a pheromone mixture of both prey species were considerably more attractive to M. setiventris and M. melancholica than the individual chemicals. Medetera seem to respond to the stage of tree decay and the intensity of bark beetle infestation via the ratios of tree volatiles and/or prey pheromones.
Functional responses of immature stages of Propylea quatuordecimpunctata (L.) to varying densities of Aphis fabae Scopoli
reared on Vicia faba L. were evaluated under laboratory conditions. All larval stages of the predator were starved for 12 h prior
to being placed individually for 24 h in plastic containers with different densities of its prey, A. fabae, on potted V. faba plants.
Logistic regression analysis of the proportion of aphids consumed as a function of initial density indicated that all larval instars of P.
quatuordecimpunctata exhibited a type II functional response when searching for A. fabae on V. faba plants. Attack rates (0.059,
0.057, 0.065 and 0.064) and handling times (6.18, 2.37, 1.06 and 0.44) for first to fourth instar larvae, respectively, were estimated
using Holling’s disc equation.
Some features of the biology and feeding relationships of small waterbugs (Notonectidae, Corixidae, Pleidae, Helotrephidae, Aphelocheiridae) and ripicolous bugs (Gelastocoridae, Ochteridae) are reviewed. Individual families are discussed as predators or as prey of other animals. Special attention is given to characteristics and relationships that affect human beings directly or indirectly. The most important relationships from the economic point of view are: bugs and blood-sucking Diptera, bugs and fish, bugs and some endangered or protected amphibians and water birds. Of less importance is the occasional use of some aquatic bugs as saprobity bioindicators. It seems that the economic importance of these bugs has been underestimated.
The main influences on the specificity of hoverfly larvae (Diptera: Syrphidae) to particular aphids are outlined. There are four main ones: aphid species, host plant, parasitoid impact and the presence of ants. Studies in the literature are used to illustrate the effect of these factors on larval performance. The use of single components of fitness as measures of performance can be misleading: only "individual fitness" includes all the appropriate components of survival, development time and reproduction. Even generalists appear to choose among aphids on the basis of expected fitness. A new level of complexity is therefore required in studies of food specificity in predatory syrphids.
The ladybird beetle Harmonia axyridis Pallas was investigated under laboratory conditions to clarify the relationship between food abundance or scarcity and ovarian development or oosorption. Four conditions were used: (1) fully fed for 24 h, (2) 24-h starvation, (3) 48-h starvation, and (4) 24-h starvation followed by 24-h re-feeding. Body length and initial body weight were not significantly related to the number of ovarioles per female. Both starvation conditions significantly increased the percentage of oosorptive individuals and ovarioles per female, and significantly decreased the percentage of mature ovarioles per female. Re-feeding for 24 h after a 24-h starvation resulted in a significantly higher percentage of mature ovarioles per female; however, the percentage of mature ovarioles remained lower than in the fully fed condition. Oosorption mainly occurred during the intermediate developmental stage of the ovarioles. The rates of ovarian development and oosorption in predatory H. axyridis were much faster compared with those in herbivorous ladybird beetles. Body length, initial body weight, and the number of ovarioles were significantly correlated with the number of eggs laid during the last 24 h of each experimental condition. From an analysis of the weight loss and the number of eggs laid during the last 24 h of each experimental condition, it appears that the realized weight of the eggs may be directly determined by the amount of food digested by the adult. The ovarian development and oosorption were asymmetric in the right and left ovaries. These may be important strategies for oviposition in H. axyridis, because selective provision of maturing ovarioles in the right or left ovary with digested nutrients would favor their development. In addition, the energy loss through oosorption during the intermediate developmental stage of oocytes would be less than the energy loss resulting from the resorption of mature oocytes. Therefore, one role of the ovary in H. axyridis, in addition to egg production, might be as a kind of energy storage system for increasing reproductive success. An immediate start of ovarian development under favorable feeding conditions and rapid oosorption during food scarcities may be an adaptive ovipositional and survival strategy for female adults of H. axyridis in response to heterogeneous and fluctuating resource conditions.