For biological control it is necessary to store mass-reared biological control agents when the demand is low. The objective of this study is to increase their shelf life without significantly reducing their fitness. The ladybird Hippodamia variegata is a widespread and voracious aphidophagous predator, with an important role in decreasing the abundance of pest aphids in many parts of the world. We investigated the effect of storage at three temperatures: constant 1°C, constant 6°C, and an alternating thermal regime of 12°C/0°C (the higher temperature for 12 h and the lower one for another 12 h). They were exposed to each of the temperature regimes for either 15, 25, 35, 45 or 60 days. We recorded survival, pre-oviposition period, fecundity and voracity of adult H. variegata following storage. The survival of adult beetles significantly declined with increasing storage duration at all three temperatures. Storage at 6°C up to 35 days and at 12°C/0°C up to 45 days had no significant effects on the fecundity of the ladybirds, but storage for longer significantly decreased fecundity. Beetles stored at 1°C for any of the durations had significantly lower fecundities. Prolonged cold storage caused an increase in the pre-oviposition period at all storage temperatures. Generally, 6°C and 12°C/0°C are the best temperatures for storing the ladybirds as they had the least negative effect on their fitness. The results of this research can help in improving the quality of H. variegata stored for use as biological control agents in the following season.
The coccinellid H. axyridis shows considerable intraspecific variability of elytral patterns. In this paper, we suggest that a genotype that confers a specific pattern of elytra could also confer other specific autecological attributes. The aim of this paper is to compare fitness parameters of two phenotypes (aulica and nigra). Aulica is a common morph characterized by two light red areas that nearly cover the whole elytra, leaving a narrow black border, whereas nigra is completely black; the latter is a rare morph that was naturally obtained from mass cultures. Intraspecific differences occur between H. axyridis phenotypes. The aulica phenotype is more voracious than nigra. Consumption rate of males is higher in aulica than in nigra, but there is no difference for females. Larval biomass of aulica is generally higher than that of nigra. The maximum body-weights reached by larval instars and adults are significantly higher for aulica. Aulica also has greater longevity and reproductive capacity. Only life stage duration of eggs and pre-pupae differ between the two phenotypes. Nigra shows lower fecundity and fertility. Our study showed that the strong differences in phenotype traits of the coccinellid H. axyridis could affect its fitness.
Our goal has been to determine the effect of the presence of aphids on voracity (measured as number of prey eaten and biomass consumed) of Coccinella septempunctata L. and Harmonia axyridis Pallas (Coleoptera: Coccinellidae) feeding upon the oblique-banded leafroller, Choristoneura rosaceana (Harris) (Lepidoptera: Tortricidae). For each coccinellid predator, treatments using a single prey species, with either 30 first instar C. rosaceana or 100 third instars Aphis pomi DeGeer (Hemiptera: Aphididae), were compared with two-prey treatments in which the two prey species were present simultaneously. For both predators, the total number of prey killed (total prey species pooled) and the total biomass consumed were significantly higher when both prey were present than in single-prey treatments. The voracity of C. septempunctata on C. rosaceana larvae was not affected by adding A. pomi, whereas that of H. axyridis declined; the voracity of both predators on A. pomi increased when C. rosaceana larvae were added. The preference for the aphids over C. rosaceana was confirmed for both coccinellid species.