Grasshopper Babies and Their Lunch Boxes — The Reproductive Strategy of the Desert Locust

Since ancient times, locusts have been among the most feared agricultural pests faced by human societies. From ancient Egypt to modern countries such as the United States and China, outbreaks of locust swarms have repeatedly caused severe damage to crops and food supplies. For this reason, understanding the mechanisms behind locust outbreaks has long been a major focus of scientific research.

Recently, a research team from Mauritania and Japan investigating the desert locust Schistocerca gregaria discovered an unusual behavior: these insects appear to prepare a kind of "packed meal" for their offspring. Traditionally, locusts and similar insects have been thought to rely primarily on producing large numbers of offspring rather than investing heavily in each individual. However, this new discovery suggests a more complex reproductive strategy.

Understanding the reproductive strategy of the desert locust

Before examining the reproductive strategy of the desert locust in detail, it is helpful to understand a key biological characteristic of this species. Desert locusts exhibit two distinct non-genetic phenotypes known as the gregarious phase and the solitarious phase. These two forms differ greatly in both appearance and behavior.

Adults in the gregarious phase typically arise under dry environmental conditions. They possess strong migratory abilities and are capable of forming massive swarms. Their nymphs display yellow and black coloration and often move collectively in large groups.

In contrast, individuals in the solitarious phase usually develop in more humid environments. These locusts have shorter wings and lack strong migratory capability. Their nymphs are uniformly green and generally live and move alone.

Differences in yolk sac size among nymphs of different phenotypes（圖片來源：Koutaro Ould Maeno，採用 CC BY-NC 4.0 授權）

Different reproductive strategies and the unique "lunch box" of locust hatchlings

The researchers found that these two forms of desert locusts differ not only in behavior and coloration but also in their reproductive strategies. Compared with solitarious females, gregarious females produce larger eggs. These larger eggs contain more yolk, which provides additional nutrients for the developing embryo before hatching.

Differences in egg size of the desert locust under different conditions. SOL indicates the solitarious phase, and GREG indicates the gregarious phase. Wet and Desiccated refer to humid and dry environments, respectively（圖片來源：Koutaro Ould Maeno，採用 CC BY-NC 4.0 授權）

The researchers also discovered that locust eggs show strikingly different developmental outcomes depending on environmental conditions. Eggs developing in humid environments typically hatch into nymphs that are more fully developed and noticeably larger than those emerging from eggs exposed to dry conditions. Gregarious-phase nymphs in particular tend to grow larger and often display darker body coloration.

Schematic diagram of the oviposition strategy of the desert locust（圖片來源：Koutaro Ould Maeno，採用 CC BY-NC 4.0 授權）

Under dry conditions, however, the researchers observed a remarkable phenomenon: the newly hatched nymphs appear to carry a special "lunch box." In dry environments, hatchlings from both phases are slightly smaller than those from humid environments, and both types display green body coloration. Yet inside their bodies they contain a much larger residual yolk sac.

Researchers refer to this retained yolk as a "lunch box." It contains large amounts of fatty acids and other nutrients required for development.

Body weight and dry weight data of desert locust hatchlings, including water content and lipid content（圖片來源：Koutaro Ould Maeno，採用 CC BY-NC 4.0 授權）

When scientists tested the starvation tolerance of these hatchlings, they found that nymphs hatched under dry conditions survived far longer without food than those from normal conditions. In particular, gregarious-phase nymphs from dry environments survived approximately twice as long as normal hatchlings.

Survival time of nymphs of different phenotypes, with circles and triangles representing solitarious and gregarious nymphs, respectively（圖片來源：Koutaro Ould Maeno，採用 CC BY-NC 4.0 授權）

What do these findings tell us?

This discovery reveals an important aspect of how desert locusts allocate nutritional resources to their offspring. The presence of the "lunch box" suggests a physiological adaptation that allows embryos developing under dry conditions to reserve energy for survival after hatching.

These findings deepen our understanding of the ecological behavior of desert locusts and may also provide new indicators for predicting future locust outbreaks. For example, by monitoring egg size or the starvation tolerance of hatchlings, scientists may be able to estimate the likelihood of large locust swarms forming.

Such knowledge could improve the ability to forecast locust outbreaks and help develop more effective strategies for controlling them. In the long term, these insights may contribute to better agricultural protection and ecosystem management.

Author: Rodrigo

Reference:

Koutaro Ould Maeno, Cyril Piou, Nicolas Leménager, Sidi Ould Ely, Mohamed Abdallahi Ould Babah Ebbe, Ahmed Salem Benahi, Mohamed El Hacen Jaavar. (2025). Desiccated desert locust embryos reserve yolk as a “lunch box” for posthatching survival, PNAS Nexus, Volume 4, Issue 5, pgaf132, https://doi.org/10.1093/pnasnexus/pgaf132