Neoclytus caprea

Neoclytus caprea (commonly called the banded ash borer) is a species of beetle in the family Cerambycidae. It was described by Say in 1824. It feeds on sapwood of ash, sometimes oak, and hickory. It often emerges indoors from firewood; logs may become infested within 20 days of felling during summer. The banded ash borer experiences sexual dimorphism, as the female of the species is considerable larger in size than the male and has yellow and black elytra coloring rather than white and black of the male of the species. They produce one generation a year.

The flight period of the banded ash borer, which is triggered by seasonal phenological mechanisms, prevents the species from cross attraction with sympatric species with similar or identical pheromone chemical composition. Neoclytus caprea emerges and flies from their host species in early spring, much earlier than species that possess 3R-ketol compounds in their chemical composition like they do, with negligible overlap between flight periods of sympatric species. This effectively isolates the banded ash borer, antagonizing and preventing the possibility of cross attraction.

Etymology
Neoclytus caprea is identified colloquially by the name of the banded ash borer in reference to a common host plant of theirs, the ash tree, which they choose to infest and feed on. The word banded is used in indication of the distinct banded pattern that decorates the back of their elytra and their abdomens, setting this particular species of beetle apart from others.

Description
Adult body sizes range generally from 8-17 mm in length, although some as large as 25mm have been recorded before. Larvae body sizes can develop to be up to 22 mm in length. Neoclytus caprea have elongated, narrow bodies with yellow and black striped abdomens akin to that of a wasp or hornet. Sexual dimorphism is prevalent in Neoclytus caprea. Females are considerably larger than males of the species, and they have yellow and black banded markings on their elytra unlike the males that have white and black banded markings on their elytra. The top two bands on their elytra loop together to produce two circular shapes, similar to eyes. There is a distinct band found behind their heads that distinguishes Neoclytus caprea from similar species. Both females and males have red-orange legs that are covered in white hairs. Their thoraxes and heads are also covered in the same white hairs.

Diet
As their colloquial name suggests, a common and preferred host plant of the banded ash borer is the ash tree, likely due to the uniquely low levels of tannins that the ash tree produces which makes it more palatable for the banded ash borer. The banded ash borer can also be found feeding on hickory, elm, mesquite, and sometimes oak. Some sources have identified wild grape trees, walnut trees, and palo blanco trees as alternate possible host plants that the banded ash borer has been observed feeding on. Larvae bore into the sapwood of ash trees, which they feed on for the summer season. Unlike other species in the genus who typically prefer freshly felled and/or weakened trees, N. caprea seems to favor seasoned wood, or wood that has been left to be dried of its moisture and sap.

Life History
Adults of Neoclytus caprea emerge from the wood in the early spring for their flight period, between the months of March and June, only emerging during the timeframe between late morning to mid-afternoon. They then search for and fly to a new suitable host plant to deposit their eggs in the bark. The larvae feed underneath the bark for some time before boring into the sapwood and feeding on it for the remainder of the summer season. It is not until fall that they pupate, and then in the spring they emerge from the wood as fully matured adults to repeat the cycle once again. Neoclytus caprea produces a single generation per year.

Distribution
Neoclytus caprea is native to North America and can be found all over the United States, except the Pacific coast, and their distribution also stretches into eastern Canada.

Physiology
The physiology of Neoclytus caprea encompasses various sensory and physiological mechanisms that contribute to its survival and reproductive success within its habitat.

Flight
Adult  Neoclytus caprea  exhibit remarkable flight capabilities, facilitated by well-developed wings and powerful flight muscles. Their ability to fly allows them to disperse over significant distances in search of suitable host plants for feeding and oviposition. Studies have shown that they can cover several kilometers during their lifetime, contributing to genetic exchange and population dynamics within their range.

Vision
Neoclytus caprea possesses a complex visual system, including specialized photoreceptors that enable them to perceive light and distinguish between different colors in their environment. Their vision is particularly acute during the daylight hours, aiding in mate selection, predator avoidance, and navigation during flight. The ability to detect colors and patterns also plays a crucial role in identifying potential mates and locating suitable host plants.

Defensive Appearance
Neoclytus caprea has conspicuous coloring and patterning on their elytra and abdomens that can make them particularly visible to predators and susceptible to predation as a result. In some cases, unpalatable and toxic prey will develop or evolve bright, conspicuous coloring to deter predators from consuming them. Their unpleasant taste is gained through their specialized diets that are often high in alkaloids and other unfavorable compounds. As soon as the unpalatable prey is consumed, the predator will avoid it with the knowledge of their unpleasant taste. For these prey, it pays to have conspicuous coloring that allows the prey to be easily identified and avoided by the predator. However, Neoclytus caprea prefers a diet of ash trees which are distinctly very low in tannins, and therefore more palatable. This generalized diet of palatable host material means that their highly visible nature can be dangerous for their survival. However, due to the distinct yellow and black banding on their abdomens, and on the elytra of females of the species, their overt visibility can sometimes be beneficial to Neoclytus caprea. This is likely because they are exhibiting an illustration of Batesian mimicry, which is when tasteful prey evolve the coloring and appearance of distasteful species, such as a wasp, to avoid predation. Their elongated and slender body assists in mimicking their target species. Predators will avoid prey models that are similar if they know one of them is noxious and distasteful. The high contrast and conspicuous coloring in this species could also prove to be a very effective warning sign that it is toxic even if it is not so, it gives the impression that it is an unfavorable morsel for consumption, this warning sign coloration that the banded ash borer utilizes is called aposematism.

Olfactory Cues
Males of Neoclytus caprea will produce and secrete pheromones containing 3R-ketol compounds that attract both sexes of conspecific beetles. Many other species in the genus have similar or even identical pheromone composition that might cause inter-species interactions. This is prevented by seasonal phenological mechanisms that cause them to fly early in the spring and avoid sympatric species that have similar male pheromone compositions, effectively isolating them from 3R-ketol producing species. seasonal phenology segregates species so they may have similar pheromone compositions but rarely ever interact. The banded ash borer also demonstrate the development of olfactory mechanisms because of their emergence and proximity to species with dissimilar male pheromone composition. The development of their olfactory system suggests strong selective forces against cross attraction and forces for mate location. Studies found that Neoclytus caprea is not influenced by compounds such as COHs, syn-diols, anti-diols, and 2-MB found in other species in close proximity to them during their flight period. Neoclytus caprea may utilize these olfactory mechanisms to avoid sexual interactions with sympatric species, or their olfactory system may not detect or recognize the olfactory cues of certain species so they are unable to register them as possible mating partners. These olfactory mechanisms encourage the banded ash borer to locate and identify suitable mating partners. The effects of host plant volatiles on attraction and mating in Neoclytus caprea was also studied, they found that host plant volatiles inhibited attraction in this hardwood feeding species of beetle. There is still no definite reasoning behind why the host plant volatiles induces this response in the attraction of banded ash borers.

Gustation (taste)
Gustatory receptors in Neoclytus caprea allow them to assess the palatability of potential food sources and distinguish between favorable and unfavorable substrates for feeding and oviposition. These receptors are particularly sensitive to chemical cues present in the sapwood of host trees such as ash, hickory, and oak. By sampling and evaluating various food sources, individuals can optimize their foraging behavior and reproductive success.

Hearing
While the auditory capabilities of Neoclytus caprea have not been extensively studied, it is likely that they possess sensory organs for detecting sound vibrations. These auditory cues may play a role in communication, predator detection, or navigation in their environment.

Thermosensation
Neoclytus caprea may possess thermosensory mechanisms that allow them to detect temperature variations in their surroundings. These sensory adaptations could influence their behavior and activity patterns in response to environmental cues such as temperature gradients or thermal cues associated with potential mate locations or suitable habitat areas. Thermosensation also play a role in regulating metabolic processes and energy expenditure in response to changing environmental conditions.

Digestion
The digestive system of  Neoclytus caprea  is adapted to process cellulose-rich plant material, particularly the sapwood of host trees. Specialized enzymes produced in the beetle's gut facilitate the breakdown of cellulose into simpler compounds that can be absorbed and utilized for energy. This efficient digestion of woody plant material allows  Neoclytus caprea  to exploit a niche resource and thrive in habitats where suitable host trees are abundant.

Microbiome
The gut microbiome of Neoclytus caprea likely plays a significant role in digestion and nutrient absorption. Microbial communities residing in the beetle's digestive tract may assist in the breakdown of complex plant polysaccharides, enhance nutrient extraction, and contribute to overall digestive efficiency. While specific microbial species and their functions remain to be fully elucidated, the gut microbiome is undoubtedly an integral component of the beetle' s digestive physiology.