Spilomyia longicornis

S. longicornis is typically 11-15 millimeters long.[3] S. longicornis has a black body with yellow markings and stripes on its abdomen.[4] Its wings are mostly clear with a dark tinge, and the anterior portion of the wings are typically darker brown in color.[4] The back four legs are yellowish in color, and the front two legs are yellow at the base and black at the ends.[4] They tend to rest on their back four legs and move their front two legs above their head, making them appear like antennae on the Hymenoptera species that they mimic.[4]

Spilomyia longicornis feeding on a flower

S. longicornis flies are part of the Syrphidae family, which is of the order Diptera. The hoverfly family is one of the most diverse in the Diptera order.[5] There are at least 200 genera and 5000 species included in this family.[5]

S. longicornis is widespread in eastern North America.[2] These flies can be found near and around flowers that produce pollen and nectar, which they feed on.[6] Also, rotting trees are an important environmental component of their habitat.[7] S. longicornis larvae are typically found in rot holes, or rotting cavities found in live trees, and develop there.[8] Almost all types of trees can develop rot holes, but they are more common for certain types of trees than others.[8] The rot holes provide a food source and protection for the larvae.[8] Thus, these damp environments are ideal for larval development.[8] Adult S. longicornis flies are most often found hovering over flowers that produce large amounts of pollen and nectar, the adults' food source.[6]

S. longicornis larvae are found in rot holes in rotting trees.[8], while adults spend the majority of their time around flowers to get pollen and nectar for food and for mating.[6] Females need pollen for reproductive development.[6]

Only adult S. longicornis flies eat the pollen and nectar from flowers.[6] Pollen has a high content of nitrogenous nutrients. Because of this, females are able to use the nutrients from pollen to develop their reproductive tissues.[6] These nutrients, which are not consumed by S. longicornis flies until adulthood, are important for vitellogenesis, also known as yolk deposition.[6] They also consume nectar from flowers and use that energy for their hovering behavior.[6]

S. longicornis males have been directly observed mate-seeking near flowers.[7]

Most Syrphidae flies mimic Hymenoptera species.[9] S. longicornis mimics vespid species including introduced species such as Vespula vulgaris.[1] S. longicornis flies mimic vespid wasps in three main ways: physically, behaviorally, and auditorily. Just like vespid wasps, the anterior portion of the wings of S. longicornis flies are a darker brown color than the rest of the wing.[4] Their abdomen is yellow with black stripes, and the thorax and head are similarly colored.[4] Behaviorally, S. longicornis flies mimic the way common wasps move their antennae.[4] By resting on their back four legs and placing and moving their two front black legs above their head, they more closely resemble wasps.[10] When threatened, S. longicornis bend their abdomen in a similar fashion to wasps who are stinging a predator.[4] They may also move their abdomen up and down when they are on a flower, which is a mimic of wasp abdomen expansion.[4] Finally, it has been documented that S. longicornis flies, when threatened, produce a different buzzing sound than normal.[11] While wasps do not necessarily produce a different sound upon attack, the sound S. longicornis makes when threatened seems to be of a frequency similar to some hymenopteran species.[11] This strategy may have evolved because the visual and behavioral mimicry may not always work.[11]