This article studies coccinellid dispersal in heterogeneous environments using some hypotheses on dispersal rates that correspond to empirical observations. It is assumed that emigration rates increase with decreasing patch payoff that is measured either as the number of aphids per a lady beetle, or as the number of aphids only. Three scenarios for immigration are considered: individuals choose patches unconditionally, immigration is proportional to patch quality, and immigration is proportional to patch payoff. Coccinellid spatial distributions corresponding to these assumptions are given by a power law. Using some data from the literature on distribution of Coccinella septempunctata it is shown that the model with emigration proportional to the ratio of the number of conspecifics to aphid density and unconditional immigration rates provides the best fit when compared with the other models. This model predicts undermatching where better patches get lower consumer density when compared with the ideal free distribution.
We investigated the predatory potential and food preference of different life stages of Coccinella septempunctata L. for a nutritious aphid (mustard aphid, Lipaphis erysimi) and toxic aphid (cabbage aphid, Brevicoryne brassicae). We provided all the life stages of C. septempunctata with either L. erysimi or B. brassicae and found that the second, third and fourth instar larvae and adult females of this predator consumed daily greater numbers of L. erysimi. However, the first instar larvae and adult males consumed similar numbers of both of these aphids. In choice condition, each larva, adult males and females were each provided separately with a mixed aphid diet in three proportions (i.e. low: high, equal: equal and high: low densities of L. erysimi: B. brassicae). We hypothesized that life stages of C. septempunctata will prefer L. erysimi regardless of its proportions. Laboratory experiments supported this hypothesis only at the adult level in terms of high values of β and C preference indices. However, it rejects this hypothesis at the larval level, as larvae preferred B. brassicae when provided with certain combinations and showed no preference in a few combinations. We infer that mixtures of nutritious and toxic aphids may enable this ladybird to overcome any probable nutritional deficiency and/or reduce the toxicity of a toxic diet, especially for the larvae. Results of the treatment in which a high proportion of B. brassicae were consumed along with fewer L. erysimi indicates that a mixed diet could be better for the development of immature stages of C. septempunctata., Mushtaq A. Guroo, Ahmad Pervez, Kuldeep Srivastava, Rakesh K. Gupta., and Obsahuje bibliografii
Larvae of Aphidoletes aphidimyza (Rondani) (Diptera: Cecidomyiidae) secrete an oviposition-deterring pheromone (ODP). In choice tests, females of A. aphidimyza laid significantly fewer eggs on Vicia faba L. plants infested with Aphis fabae Scopoli (Homoptera: Aphidoidea) that were previously exposed to conspecific third-instar larvae or a water extract of their ODP.
A. aphidimyza females also laid fewer eggs on aphid-infested plants that were previously exposed to unfed first-instar larvae of Chrysopa oculata Say, Chrysopa perla (L.) or Chrysoperla carnea (Stephens) (Neuroptera: Chrysopidae), or second-instar larvae of Coccinella septempunctata L. (Coleoptera: Coccinellidae). However, the response to traces of C. carnea larvae was very weak.
From 1994-1997 the food of Coccinella septempunctata L. was investigated on the basis of gut dissections of adults and larvae collected in the field. Additionally, the gut contents of adults fed under laboratory conditions were investigated. The likelihood of recovering different prey types during gut dissection was variable, which will be illustrated by presenting some common prey fragments. The food eaten by adult C. septempunctata throughout a year was studied at a locality in Berlin-Staaken. Ladybirds were collected from March 1994 until November 1997 in different crops and habitats on roughly a monthly basis. Aphid feeding was detectable from April until October. In May and June they were the most frequent food type. Fungal spores, in most cases the conidia of Alternaria spp., became most frequent in July. Additionally non-aphid arthropods were frequently preyed upon in July. A very common non-aphid prey item were thrips. Pollen was important in May and September. Comparing the food components of newly emerged adults with those of overwintered adults some remarkable differences were detected. In newly emerged adults non-aphid arthropods and fungal spores were much more frequent than in overwintered adults whereas aphids were less frequently found. The diet of adults and larvae was also investigated in June and July in cereal fields at two other localities, Northern Flaeming and Magdeburger Boerde. No difference in adult diet was found between the three localities. The composition of the larval diet was relatively similar to that of the adults., Holger Triltsch, and Lit
The impact of the arrival of the exotic coccinellid Harmonia axyridis on the biological control and dispersion of apple mites and aphids, and on the vertical distribution of the established coccinellids Coccinella septempunctata and Coleomegilla maculata have been studied. Assemblages of adults of the three coccinellid species were tested on apple saplings and on apple trees against Aphis citricola and Tetranychus urticae. The presence or substitution of adults of H. axyridis for adults of C. maculata or C. septempunctata did not reduce the predation impact on mite or aphid prey. H. axyridis was a more efficient predator of mites than was C. septempunctata and generated lower prey dispersal from host plants. Substitutions of adults of H. axyridis for those of C. maculata, and in some cases of C. septempunctata, resulted in greater reduction in number of aphids. On apple trees, the three coccinellid species occurred at different heights. Neither C. maculata nor C. septempunctata modified their vertical distribution on apple tree over a 24 hour period in response to the presence of H. axyridis.
Development and survival of larvae of two predatory ladybird species, Harmonia axyridis (Pallas) and Coccinella septempunctata L. on hibiscus (Hibiscus syridis L.) trees was followed daily outdoors during four seasons. Data were analysed and stage-specific mortality in a stage-structured model was estimated using Manly's (1997) method. Subsequently, key factor analysis was used to determine the life stages in which the daily mortality was best correlated with the total mortality during larval life. Consistently with the results from the first two years, the larvae suffered the greatest mortality during the first and fourth instars. The k-values for these two instars were also best correlated with those for the whole larval life, especially in H. axyridis.
In a laboratory experiment, we investigated the preference of larvae and adults of Coccinella septempunctata (Coleoptera: Coccinellidae) for three aphid species: two essential prey, Acyrthosiphon pisum and Aphis philadelphi, and a toxic prey Aphis sambuci. Surprisingly, the toxic aphid was consumed at twice the rate of the two essential prey species. The stages and genders of the ladybirds did not differ in their preference for aphid species. In the tritrophic interaction, in the field, on the elder host plant Sambucus nigra, A. sambuci is usually avoided by C. septempunctata. To measure ladybird preference, apterous females of the three selected aphid species were released in a Petri dish followed by a ladybird. After four hours, we removed the ladybird, counted the number of aphids of each species that survived, and calculated the number of aphids of each species consumed in total. We examined preference by considering separately the first two aphids consumed by a predator (early feeding), and all remaining aphids consumed thereafter (late feeding). The consumption rates of the first two individuals did not deviate from expected values with no preference; i.e., ladybirds fed on aphids without choice in the beginning of experiment when they were hungry. The ladybirds did express preference thereafter, but our hypothesis that the ladybirds should be able to distinguish among the aphids during later phase of the experiment and choose the most profitable species, or at least distinguish between essential and toxic prey, was rejected.
The life tables of the aphid predators Coccinella septempunctata L., Ceratomegilla undecimnotata (Schneider) and Propylea quatuordecimpunctata (L.) (Coleoptera: Coccinellidae), fed on Aphis fabae Scopoli (Hemiptera: Aphididae), were constructed at constant conditions (25 ± 1°C, 65 ± 2% RH; 16L : 8D). The average total fecundities of C. septempunctata, C. undecimnotata and P. quatuordecimpunctata were 1996.8, 1160.5, and 724.6 eggs / female, and the average longevities were 94.9, 88.3, and 68.9 days, respectively. The net reproductive rates (Ro) were 1004.1, 544.3, and 375.1 females/female, and the intrinsic rates of increase (rm) 0.118, 0.142 and 0.166 females/female/day, respectively.
Since 1978, the abundance of Coccinella septempunctata L. has been recorded at a hibernation site in the western Czech Republic. Over the years, abundance varied by two orders of magnitude and a long-term trend for decrease in C. septempunctata abundance was observed beginning in the early 1990s. This recession was correlated with the decreasing abundance of its dominant prey, cereal aphids. The acreage of small grain cereals and other crops suitable for breeding C. septempunctata populations also decreased. The change in abundance of cereal aphids may be associated with a dramatic decrease in fertilizer input after 1990. Decreasing fertilizer use has changed the quality of small grain cereal crops and is reflected in lower yields.
Mate choice, reproductive success and fecundity of typical and melanic morphs of C. septempunctata were studied. Melanic as well as typical individuals preferred to mate with melanic males and females. Mate choice was mainly determined by females and to a lesser degree by males. Mating duration, oviposition period, and lifetime fecundity were highest (51.20 ± 2.82 min, 47.00 ± 2.79 days and 705.40 ± 69.85 eggs) when a melanic female mated with a melanic male and lowest (38.94 ± 1.68 min, 26.10 ± 2.54 days, 395.9 ± 36.25 eggs) when a typical female mated with a typical male. Longevity of both sexes of melanics was higher than of typicals. The fecundity function of both morphs was triangular but the daily oviposition was irregular. In melanic and typical females the peak oviposition (66.40 eggs/day and 48.30 eggs/day) occurred on the 23rd and 14th day of the oviposition period, respectively. Oviposition peaked earlier in typical females, but peak oviposition was higher and the oviposition period longer in melanic females. The higher reproductive success of melanics may favour this morph over typicals.