hungerford: anatomy of simulium vittatum. 369 



two longitudinal rows on the ventral surface; the three blood 

 g-ills at caudal end, unbranched. 



Pupa. The thoracic respiratory filaments each consist of a 

 single main trunk, from which arise eight branches, each of 

 which divides into two, thus making 16 twigs in all. Near 

 the basal margin of the last few abdominal segments are a 

 few caudal-projecting dorsal hooks, and on the tip of the last 

 segment is a pair of blunt spines. The pupal case is of the 

 wall-pocket type, from which the respiratory filaments of the 

 pupa project. 



GENERAL HABITS AND LIFE HISTORY OF THE FAMILY. 



The habits of the adults are quite generally known because 

 in many places they are fully as troublesome as mosquitoes. 

 They are so-called "bloodsuckers," feeding upon the blood of 

 horses, cattle, and man, sometimes to such an extent as to be 

 of considerable economic importance. (See Riley in N. Y. 

 State Mus. Bull. No. 68.) They lay their eggs on the surface 

 of rocks over which shallow water is flowing rapidly, as on 

 the rocks of shallow rapids and the ledges of waterfalls. Their 

 eggs are laid in masses one layer deep. In about eight or ten 

 days they hatch into larvse which attach themselves by their 

 caudal end to the rocks or stems of aquatic plants. 



The larvae retain their position in the swiftest current by 

 means of a disc-like sucker on the posterior end of the body. 

 When they desire to move to a new location they may do so by 

 anchoring a silken thread to the support and, releasing their 

 hold, spinning out their silk as they are washed downstream, 

 but retaining control of it very much after the fashion of 

 spiders suspending themselves in mid-air, or they may travel 

 over the surface of the rocks with a looping gait similar to 

 that of a measuring worm. 



They are said to feed upon algsB, diatoms, and parts of 

 phaneragamous plants.* ~ In those I have examined diatoms 

 have comprised most of the material found in the digestive 

 cannal. 



When the larva is ready to transform it spins a tough pupal 

 case firmly attached to the rock and changes to a strangely 

 shaped pupa. Then in due time the fly comes from the pupal 

 skin, rises to the surface of the Avater and shortly takes flight. 



" Miss R. Phillips, 1890, cf Cornell ri\iversity. roports that amoiiE the alga? taken by 

 the larvae are Nothix, Cladtjihora, and Vatichera. Walter T, Emery adds Conferva. 

 Soenedesnuis, Chlaniydonionaj , J^iUglena. 



