This week’s insect is a particularly recognizable member of one of the largest families of beetles, the ground beetles (Carabidae). Colliuris pensylvanica, commonly called the long-necked ground beetle, is strange in that its pronotum and posterior area of the head are stretched and elongate, giving it a giraffe-like appearance. In fact, when Linnaeus described it he placed it in the genus Attelabus, a genus of weevils that sometimes have elongate necks (close relatives of the giraffe weevil).

As stated above, Linnaeus first described this species in 1767 as Attelabus pensylvanica; it was later moved to the genus Colliuris (probably by Degeer who erected the genus). Not only have there been numerous synonyms for this species (including Casnonia picta, Casnonia limbata, Colliuris picta, and Colliuris yucatana), but also the species name has been variably spelled pennsylvanica, pensylvanicus, and pennsylvanicus (for obvious reasons).

This species is unlikely to be confused with any other ground beetle, let alone many other beetles. It is generally around 6mm long, with a long head and pronotum, but typical in form otherwise. Coloration is key for distinguishing it from other members of the genus. The head and pronotum are black, and the antennae are black except the basal portion which is lighter. The elytra are a striking red or orange, with black markings in the middle (forming three spots) and the tips. The legs are a light amber color.

As with most ground beetles, Colliuris pensylvanica is a predator. Very few observations have been made regarding a specific diet, but it probably feeds on small insects and other arthropods that it can catch (it appears to have smaller mandibles than many of its relatives). Its common presence in soybean fields may mean it also has the potential to help control pest populations, especially aphids. Ground beetles are not only built for attacks, but are also good at defending themselves. Colliuris pensylvanica does this in several ways. First, it has been suggested that it resembles an ant for protection. Second, it produces both acetic and formic acid (the latter adding to its ant-like characteristics) along with a few other defensive chemicals (Will et al. 2000). Colliuris pensylvanica also apparently has stridulatory files on their wings to produce sound. This species is often also attracted to lights.

Colliuris pensylvanica is found in many habitats, but may prefer wet, marshy areas. They can be found among leaf litter, rotting logs, and the ground among vegetation where they search for prey.

There are 4 species of Colliuris found in America north of Mexico, and C. pensylvanica is the most widespread. It is found throughout the continental US and into southern Canada.

• Will KW, Attygalle AB, Herath K. 2000. New defensive chemical data for ground beetles (Coleoptera: Carabidae): interpretations in a phylogenetic framework. Biological Journal of the Linnean Society, 71: 459–481. doi:10.1006/bijl.2000.0456 [PDF]
  
• Colliuris pensylvanica on Bugguide
• Colliuris pensylvanica on GBIF