page_title: Asilidae
section_title: Adult
hierarchical_section_title: Asilidae / Morphology / Adult
context_page_description: The Asilidae are the robber fly family, also called assassin flies. They are powerfully built, bristly flies with a short, stout proboscis enclosing the sharp, sucking hypopharynx. The name "robber flies" reflects their notoriously aggressive predatory habits; they feed mainly or exclusively on other insects and as a rule they wait in ambush and catch their prey in flight.
context_section_description: Adults are generally medium to large in size, with an average body width of 1 to 1.5 cm but with a range of 3 cm to more than 5 cm in length. The shape is generally elongated, due to the conformation of the long tapering abdomen, however there are also compact species with broad abdomens. The integument is covered with thick hair, especially on the head and thorax and liveries are often showy, with colors ranging from brown to black to grey, sometimes in contrast with other colors such as red and yellow. Frequently they are aposematic, imitating the livery of Hymenoptera.
  The head is free and mobile and dichoptic in both sexes and has three ocelli arranged in a characteristic depression formed by the elevation of the compound eyes. This feature is clearly visible in the front view and is a morphological peculiarity of Asilidae. The occipital region has one or more rows of bristles aligned behind the posterior margin of the eye. The facial region has a convex profile with a characteristic dense bundle of bristles, called a "mystax". The mystax helps protect the head and face when the fly encounters prey bent on defense. Other bristles are arranged on the ocellar tubercle.
  The antennae are of the aristate type, composed typically of five segments but sometimes from three to four, depending on the structure of the stylus. The scape and pedicel are generally relatively short and hairy; the third segment (or first flagellomere) has an oval or oblong shape, is generally longer than the two basal segments, and bears a stylus generally composed of two segments, of which the basal is very short. In some asilids, the stylus can be monoarticolate or absent.
  The mouthparts are short and modified for piercing-sucking. They consist of a strongly sclerotized proboscis which includes the labium and maxillae which form a food canal, the labrum and a piercing organ, the hypopharynx. The proboscis is rounded in cross section or laterally or dorsoventrally compressed and is usually stout, and straight and sometimes able to penetrate through the hard integument of Coleoptera. The maxillary palpi are at the base beside the labium, two-segmented in all Dasypogoninae or single segmented in Asilinae and Leptogastrinae.
  The thorax is robust and compact. Unlike in other lower Brachycera it bears long bristles (macrochaeta) useful as taxonomic characters. Bristles of this type are always present on the notopleuron (notopleural bristles) and, in two series, on mesonotum (dorsocentral, supralar and postalar). Other bristles are present on the metanotum (dorsocentral bristles on the ventral episternum and at the apex of the mesoscutellum.
  The legs are relatively long and strong, with many macrochaetes performing a raptatorial function. The wings are well developed, often relatively narrow for speedy flight; the alula is generally well developed, with the exception of Leptogastrinae and part of Dasypogoninae. The venation is much as in Rhagionidae, Tabanidae and Therevidae; the radial R is always four-branched, with R2+3 unbranched. Details of wing venation determine subfamilies and lower taxa. The wings are most often hyaline, but sometimes smoky or dark colored, or partly infuscated in many genera or completely darkened.
  The abdomen consists of 6–8 visible segments preceding the genitalia in males, but the eighth segment is sometimes entirely or partially concealed, and terminal forming the ovipositor. It is long and narrow conical in most species but wide, dorsoventrally flattened and short in bee mimics. In Leptogastrinae the abdomen is extremely long and slender. In some tribes, the male undergoes axial torsion of 180 degrees.
caption: Choerades fimbriata: a powerful predator with body adapted to fast flight. Note the mystax, the proboscis and the depression between the eyes.
exif: {"Image Orientation": "Horizontal (normal)", "Image XResolution": "240", "Image YResolution": "240", "Image ResolutionUnit": "Pixels/Inch", "Image Software": "Adobe Photoshop CS2 Windows", "Image DateTime": "2006:07:27 17:57:33", "Image ExifOffset": "164", "Thumbnail Compression": "JPEG (old-style)", "Thumbnail XResolution": "72", "Thumbnail YResolution": "72", "Thumbnail ResolutionUnit": "Pixels/Inch", "Thumbnail JPEGInterchangeFormat": "302", "Thumbnail JPEGInterchangeFormatLength": "3913", "EXIF ColorSpace": "Uncalibrated", "EXIF ExifImageWidth": "2688", "EXIF ExifImageLength": "2000"}