DIPTERA. 453 



THEREVA, Latreille, 



T. plebeia. Black, witfccinereous hairs; abdominal annuli margined with 

 white. On plants. 



Sometimes the palpi are exterior. The last joint of the antennae is either 

 almost globular or reniform, or nearly ovoid or conical, and terminated by a 

 long seta. 



The tarsi are furnished with three pellets. They form the genus 



LEPTIS, 



Which is divided into several subgenera. We may notice the 



L. vermileo. Resembling a tipula ; ^yellow ; four black streaks on the 

 thorax; the abdomen elongated, with five ranges of black spots; wings 

 immaculate. 



The larva is almost cylindrical ; its anterior portion is much the smallest, 

 and there are four mandibles on the opposite extremity. It resembles a stick- 

 like geometra (caterpillar), and is equally rigid when withdrawn from its 

 domicile. It bends its body in every direction, advances and moves about in 

 the sand, and excavates there an infundibuliform cavity, at the bottom of 

 which it secrets itself either entirely or partially. If an insect be precipi- 

 tated into the trap, it rises suddenly, clasps it with its body, pierces it with 

 the stings or hooks of its head, and sucks it. It flings away the carcass as 

 well as the sand, by bending its body, and then suddenly relaxing it, like a bow. 



The pupa is covered with a layer of sand. 



The other Tanystoma of our second division have their wings incumbent 

 on the body.. The antennae terminate in a palette, almost always accompanied 

 by a seta. The palpi of the greater number are flattened or laminiform, and 

 laid on the proboscis. 



These characters, a body compressed on the sides, a triangular head, slightly 

 projecting in the manner of a snout, the abdomen curved underneath, and 

 long, slender legs furnished with little spines, particularly distinguish the 

 genus 



DOLICHOPUS, Latreille, Fabricius, 



Which now forms a small tribe. These insects are frequently green or 

 cupreous. The legs are long and very slender. They are found on walls, 

 trunks of trees, &c. Some of them run along the surface of the water with 

 great celerity. 



FAMILY III. 



TABANIDES. 



OUR third family of the Diptera is characterised by a salient proboscis, 

 usually terminated by two lips with projecting palpi, by the last joint of the 

 antennae being annulated, and by a sucker composed of six pieces: it 

 comprises the genus 



