Broadhorned Flour Beetle

The broadhorned flour beetle is about 3.5 to 4.5 mm long and is red-brown in color. The males have a pair of broad, stout horns on their mandibles. These beetles show sexual dimorphism, with males exhibiting larger body sizes and distinctive characteristics such as enlarged mandibles, widened genae, and two small horns on the vertex. These physical traits are not observed in females.

The broadhorned flour beetle is a stored product insect found all around the world, more commonly in warm, tropical areas. In warmer regions, this beetle is often found in cassava root and cotton, whereas in the colder regions such as the temperate climate of the UK, it is often found in flour and provender mills. This is due to their increased susceptibility to colder climates and innate desire to shelter from the cold.

Gnatocerus cornutus mainly feed on various types of grain, yeasts, and flours. The broadhorned flour beetle undergoes 4 major life stages: egg, larvae, pupa, and adult. The total developmental time is about 47 days, about 1.5 times longer than the Tribolium castaneum, or red flour beetle. In the larval stages of broad-horned flour beetles, the quality of their diet influences their development rate without affecting their survival significantly. Larvae with poor quality diets can survive, although they experience a prolonged developmental period compared to those with access to higher food quality. The development rate of broad-horned flour beetles is also affected by larval density. As larval density increases, time for development from mature larvae to adults extends, affecting body size and secondary sexual traits. This delayed development is believed to be in response to heightened tactile stimulation between neighboring larvae. Increased larval density also increased mortality rate and cannibalism where larvae were seen eating pupae and other larvae. Moreover, individuals consuming higher-calorie diets exhibit enhanced survival and faster development, growing larger much more quickly. These beetles are in better condition, enabling the allocation of resources to both naturally and sexually selected traits. …