Key Points
- A recent study found that interactions between juvenile and adult desert locusts (Schistocerca gregaria) affect the behavior, development, and pheromone emissions of nymphs, with effects depending on the developmental stage and duration of exposure.
- Desert locusts use distinct pheromones at different life stages to mediate aggregation, and disruption of these signals through cross-stage interaction can affect synchronization, increase cannibalism risk, and influence swarm cohesion.
- By uncovering how cross-stage interactions shape locust development and survival, the research offers new insights for designing more effective locust control strategies and underscores the need for further studies on life-long behavioral and physiological impacts.
A joint study between the Institute for Ecological Chemistry (Berlin, Germany), the International Center of Insect Physiology and Ecology (Nairobi, Kenya), and the Institute for Advanced Chemistry of Catalonia (Barcelona, Spain) investigated how cross-stage interactions between juvenile and adult locusts influence cohesive behavior, development, and physiology, as determined by pheromone emissions. Using cage assays and chemical analysis based on coupled gas chromatography-mass spectrometry (GC-MS), the researchers studied how cross-stage interactions between the two sets would influence the behavior of the juvenile group. The team evaluated the short- and long-term cross-stage of the elder group on the younger group. The results of the study reveal the complexity of gregarious locust biology, as well as areas for future scientific exploration. A paper based on the research has been published in Scientific Reports (1).
Locusts are unique among the grasshopper family (Acrididae [2]) because these insects can occur in two phases—a harmless and cryptic solitary phase, and a swarming, more sociable phase (3); the latter poses a significant threat to crops and forage and food security (4). Schistocerca gregaria, commonly referred to as the desert locust, is the best-known species owing to its wide distribution (North Africa, the Middle East, and the Indian subcontinent) as well as its ability to migrate over long distances (2). Chemical communication among locusts is stage-specific, with both sexes of nymphs releasing aggregation pheromone and mature males producing an adult aggregation pheromone (5).
Desert locust outbreaks can be highly destructive, with swarms made up of an estimated 40–80 million insects per square kilometer migrating over vast distances (6). Each locust can consume food equivalent to twice its body weight (about 2 g) daily, totaling approximately 339 g over its lifetime (7). An important aspect of gregarious desert locust amalgamations is cross-stage interactions between different populations and stages, which may positively or negatively affect locust biology. Understanding short- and potential long-term cross-stage interactions is essential for improving locust management strategies, and coming to this understanding was a major factor in the inspiration for the researchers’ work.
For the study, a gregarious colony of the desert locust S. gregaria was obtained from the Insect and Animal Breeding Unit (IABU) of ICIPE (International Centre of Insect Physiology and Ecology, Nairobi, Kenya), and mixed sexes were reared in glass-fronted aluminum cages in a well-ventilated room with a duct system that maintained negative pressure. The different developmental stages were kept separately in cages, and fresh grass and wheat bran were provided to the insects every day. Volatiles were collected from recipient and control 3rd instar nymphs exposed (20 each) for 24 h for short-term cross-stage interactions and from individual recipient males divided thusly; exposed to adult males and females during development; not exposed to adult volatiles; exposed to male and female nymphs; and not exposed to nymphal volatiles. Aliquots of each sample were analyzed using the GC-MS technique mentioned previously (1).
