Life cycle and production potential of a traditionally eaten phloem-feeding planthopper (sakondry,Zanna tenebrosa) in Madagascar

Abstract

Zanna tenebrosa (Hemiptera: Fulgoridae), a traditionally eaten phloem feeding planthopper known as sakondry, has received recent attention for its farming potential; these insects have been successfully cultivated on bean plants in remote, rural communities that depend on natural resources for their food security, without increasing the loss of local wild habitats. Yet production is currently limited by the lack of knowledge on the basic life history and ecology of this insect. This study examinedZ. tenebrosa’s: (1) life cycle; (2) growth curves under various rearing conditions; and (3) the potential of the insect for sustainable food production, considering its feed conversion ratio (FCR) and nutrient retention. TheZ. tenebrosa life cycle was characterised by five instars of nymphs, followed by adulthood. Managed, outdoor free-range populations appear to be the ideal rearing choice in rural settings; free-range insects were significantly heavier and had shorter life cycles than those reared in enclosures on plants or cuttings. Mortality was highest in during the fifth instar (when insects are harvested), and phloem needs are likely high.Z. tenebrosa’s feed conversion ratio (1.3) was significantly more efficient than other livestock and insect meats. Further, unlike traditional meats that return only a fraction of the edible nutrients they consume,Z. tenebrosa providedmore nutrients than the edible portion of their feed. Their calorie and protein retention were three to 15 times higher than other livestock or insect meats and eatingZ. tenebrosa provided two, five, and 16 times the amount of iron, zinc, and fat than the edible portion of its feed would have provided. To our knowledge, this is the first time such amplification has been found in an animal raised for its meat. Our findings indicate thatZ. tenebrosa has promise as a farmed insect, particularly for remote malnourished communities with little access to land or infrastructure.