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 large bodied beetle is primarily brown, but has orange colouration on its elytra.[2] Depressions can be see on each side of the pygidium, which is a characteristic of males.[2] Additionally, the genital capsule, which is quite distinct, can not be seen from an overhead view.[2] Eggs produced by adults are milk coloured 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] C. 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 bee creates, which are often closely located 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.[1] The 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 fall to the ground and bury themselves. This 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]

Being capable of attacking undamaged fruits and vegetables makes the genus Carpophilus a large threat to economic crops.[3] C. lugubris, is a common pest of corn in North America, but tomato plants are also at risk.[2] Larva present in corn kernels often go undiscovered and this can lead to their rejection and subsequent discarding.[1] They 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 ability to disperse via flight gives this genus great potential for disease transfer. A related species is known to be parasitic to honey bee hives, in which they burrow into the hive and predate the larva.[2] The use of the dusky sap beetle to fight fungal infections is a possibility as well.[5]

Insecticides are not often applied in direct response to C. lugubris, but they are still effective when targeting other species.[1] A more effect 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] In Carpophilus sayi, pheromones from C. lugubris, are used to trick the species into believing a food source is nearby.[4] Similarly, traps with fermenting fruit will be placed in crop locations and the capture rates are quite high. However, when crops begin to ripen, the traps are selected against.[4] Methods involving the use of radio frequencies is a possible way of killing larva hidden in the fruit.[6] Early corn planting, in North Carolina, has show to reduce the number of damaged plants, as opposed to later planted crops.[1]

• Dusky sap beetle at Bugguide