Carpophilus lugubris

A long-lived species, the dusky sap beetle can live as an adult for up to 300 days.[1] Measuring 3.3-4.5 mm, this beetle is primarily brown but has orange colouration on its elytra.[2] Depressions can be seen on each side of the pygidium, which is a characteristic of males.[2] Additionally, the genital capsule, which is quite distinct, cannot be seen from an overhead view.[2] Eggs produced by adults are white and oval in shape.[1] Similarly, the larvae can be white or yellow in body colour, with a brown head.[1] This image, taken from Marini 2013, can provide a better look at the adult morphology and colouration.

Like other sap beetles, fruit secretions are the primary food source, but they will also consume fungi, decomposing fruit and even pollen.[1] Carpophilus lugubris is capable of feeding on undamaged fruits as well, corn being its primary food source.[1] The species is long-lived, so they will take up shelter in adverse environmental conditions. One such refuge is the bottom of beehives, which are often located close to crops.[2] Going underground during the pupa and adult stages allows them to survive the winter.[1] Larva and adults will often have overlapping niches, with the larva developing on the ears of the corn and eventually feeding on the kernels.[2]

Native to North America, C. lugubris can be found throughout southern Canada, the United States, and as far as South America.[1] Reports have even indicated its spread to southern European countries, such as Italy.[2] Only very cold climatic regions are free of the genus Carpophilus.[3]

Like the typical beetle life cycle, C. lugubris has four life stages: egg, larva, pupa and adult. Eggs are often laid on the silk of corn and have a generation time of 2–4 days. 3-5 eggs will be laid at a time and the optimal temperature is 21 °C.[1] The larval stage begins feeding on corn kernels and undergoes 3-4 instars before entering the pupa stage. This stage will often last for roughly 3 weeks.[1] When ready to pupate, the larva falls to the ground and buries itself. Pupation may last 9–10 days before reemerging, but it can be longer if overwintering becomes necessary.[1] Once exiting from the ground, the adult will use pheromones to locate a new food source and possible mating location.[1]

The ability to attack undamaged fruits and vegetables makes the genus Carpophilus a large threat to economic crops.[3] Dusky sap beetle is a common pest of corn in North America, but tomato plants are also at risk.[2] Larvae present in corn kernels often go undiscovered and this can lead to their rejection and subsequent discarding.[1] The beetles can also act as vectors for fungi transfer to crop plants.[1] Related species act as vectors for disease, such as oak wilt.[4]

The use of the dusky sap beetle to fight fungal infections is a possibility as well. This involves using the beetle to deliver Bacillus subtilis, a bacterium which kills the fungus Aspergillus flavus.[5]

Insecticides are not often applied in direct response to C. lugubris, but they are still effective when targeting other species.[1] A more effective approach is to ensure that crops are not left unharvested, as these plants will provide food for overwintering individuals.[1]

The use of pheromones by Carpophilus species has influenced traps and lures to protect crops.[4]

Radio frequency irradiation is a possible way of killing larvae hidden in the fruit.[6]

In North Carolina, early corn planting has been shown to reduce the number of damaged plants when compared with later planting.[1]

• Dusky sap beetle at Bugguide