486 INSECTA. 



those last mentioned. They frequently alight on the ground, on walls ex- 

 posed to the sun, and on leaves. 



Our second general division of the Tanystoma is characterized by 

 a membranous proboscis, usually with a short stem, projecting but 

 slightly and terminated by two very distinct and raised or ascending 

 lips. 



The form of the head in the larva) of the last Diptera of this divi- 

 sion is variable. 



In some — Lcptides—ihe wings are distant and exhibit several 

 complete cells. The antennas arc not terminated en palette. The 

 palpi are filiform or conical. 



Sometimes these palpi are withdrawn into the oral cavity. The 

 antennas have a fusiform termination or one resembling an elongated 

 cone, with a little articulated stilet at the end. 



Thereva, Lat. 

 T.pleheia. Black, with cinereous hairs; abdominal annuU 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. vermilco. llesembling a Tipula; yellow; four black streaks on the 

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

 maculate. 



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 stick-like geometra (caterpillar), and is equally rigid when withdrawn from 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 domicil. 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 secretes itself either entirely or partially. If an Insect be preci- 

 pitated into the trap it rises .suddenlj', 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 Tanyetoma of our second division have their wings in- 



