The multicoloured Asian lady beetle Harmonia axyridis (Coleoptera: Coccinellidae) may potentially exploit a range of "alternative" food sources. The nutritional value of three common non-prey food groups, i.e. fruit, fungi and pollen, is examined in this study. Development, reproduction and survival of the species were assessed in the laboratory on diets of apple, pear and raspberries and the fungi Oidium lycopersicum, Botrytis cinerea, Sclerotinia sclerotiorum and Rhizoctonia solani. When fed exclusively on these foods this ladybird failed to complete its development or reproduce. However, larval and adult survival was prolonged by 4 to 8 days and 55 to 67 days, respectively, when fruit was offered compared with only water. During a field study H. axyridis adults were collected monthly from March to October at two locations near Ghent, Belgium. Gut analysis demonstrated that, despite the continued presence of aphids, over 90% of all the adults collected contained pollen throughout the year. The pollen belonged to 53 different pollen types. Monthly average numbers of pollen grains in the gut varied from 5 to 233 grains. In contrast, there were about 35,000 grains in the guts of H. axyridis females that successfully developed and reproduced in the laboratory on diet that consisted of only pollen. This suggests that in the field in the majority of cases pollinivory mainly only provided complementary nutrients for this coccinellid. The use of alternative non-prey foods like pollen and fruit may play a role in sustaining populations of this coccinellid at times when the optimal prey is absent.
The relationship between body size and reproduction was investigated for two laboratory strains of Podisus nigrispinus (Dallas). A strain originating from Surinam and maintained for about 15 years under laboratory conditions, did not demonstrate any significant relationship between body length and fecundity. A second strain originated from Brazil where it had been reared in the laboratory for several generations but under different conditions of climate, food and housing. In the first generation of the Brazilian strain, a significant positive relationship was found between body length and total number of eggs. Results suggest that colonization might act initially in favour of a positive body size/fecundity relationship. In contrast, females of the fifth and tenth generations, like those of the Surinamese strain, showed no significant relationship between body length and reproduction. Fecundity of the tenth generation of the Brazilian strain, with an average of 317 eggs per female, was significantly greater than that or the first and fifth generation, with 220 and 243 eggs per female, respectively. The strain from Surinam, with 545 eggs per female, had a markedly higher reproductive capacity than any generation of the Brazilian strain. Adult body weights of different generations of the Brazilian strain increased consistently from the first to the tenth generation, indicating an adaptation to the new environment. Females and males of the Surinamese strain lived longer than those of the Brazilian one. Besides differences related to the geographical origin of the strains, greater fecundity and longevity in long-term laboratory strains of P. nigrispinus may reflect selective adaptation to food and climatic conditions in the laboratory environment.
One factor limiting the adoption of aphidophagous coccinellids in augmentative biological control is cost-effective mass production. The use of factitious foods may lower production costs by reducing space and manpower requirements for mass rearing of the predator and its prey and by enhancing mechanization of rearing procedures. The objective of this study was to compare the efficiency of food conversion, consumption indices and growth rates of first to fourth instars of Adalia bipunctata when fed either a mixture of Ephestia kuehniella eggs and fresh bee pollen, or on the natural prey Myzus persicae. Larval survival did not differ among treatments, averaging 80 and 90% on the respective diets. Mean dry body weights of the coccinellid were significantly lower on M. persicae than on the factitious food only for second instars and the pre-pupal stage. Dry food consumption by the predator throughout larval development averaged 20.61 mg on factitious food and 14.82 mg (corresponding to an average of 284 third and fourth instars) on M. persicae. The efficiency of conversion of ingested food for total larval development averaged 25 and 30% on factitious food and aphids, respectively. The relative growth rate of the larval instars was higher on aphids, whereas the consumption index was higher on the mixture of E. kuehniella eggs and pollen. An additional experiment showed that rearing the previous instars on the factitious food had no substantial effect on aphid consumption in the fourth instar. The study suggests that this factitious diet may be an appropriate food source for mass rearing A. bipunctata.