228 



THE AMEEICAN 



On page 174, under this same caption, we 

 published an account of a worm which, by 

 spinning a web in the water, proved very de- 

 structive to young trout in certain breeding 

 ponds in the States of New York and Ohio. On 

 page 211 we stated that this worm was the larva 

 of a Two-wiuged Fly, belonging to the genus 

 Simulium. 



The habits of these larvas are not yet com- 

 pletely known; and, as everything that bears 

 upon the subject will prove interesting, and aid 

 future observers, we make room for the follow- 

 ing original observations of two of our con-es- 

 pondents. Mr. Seth Green, of Mumford, N. Y., 

 says : 



We find these larvse exclusively upon stones 

 in swift-running and rippling water. In a state 

 of rest, fastened by the "sucker" at the end of 

 the tail, they stand erect and move around with 

 a circling motion of the head. They move from 

 place to place by fastening the "tubercle" which 

 is under the thorax, and by bringing up the tail 

 end to it. The thread comes from the head end, 

 but whether from the tubercle or not, my glass 

 is not strong enough to discover. I think that 

 this larva leaves a thread wherever it goes. At 

 any rate, while putting those I sent to you into 

 the bottle, they invariably dropped from the 

 stick, leaving a thread behind them by which 

 they could be lifted and moved from side to side 

 in the water; and as, in taking away the stick, 

 the thread became fastened upon the mouth of 

 the bottle, we saw three or four at once actually 

 climbing up these threads — not so fast as a 

 spider would, but still at a pretty good pace. 



"Writing of the same larva, Sara J. McBride, 

 also of Mumford, N. Y., says: 



"When about to change its position, it works 

 for a few seconds with its maxillae against the 

 substance to which it adheres, and then, placing 

 the last segments of its body firmly on the place 

 thus prepared, moves its head off in another 

 direction. Every time it moves its head, it 

 leaves in the place a silken thread, something- 

 like a spider's thread, but much more delicate 

 and fine. After it has been in one place a short 

 time it leaves a " web," which is uneven and 

 irregular in its angles and outline. "When 

 frightened this larva remains suspended in the 

 water by means of its thread. 



I have never observed it feeding on any 

 aquatic plant, and so conclude its nourishment 

 must consist of animalcules. "Whether its web 

 is for the purpose of securing its food, or the 

 natural result of moving its head from place to 

 place, I cannot ascertain. It exists in the larva 

 state in running water, during the winter 

 months, and spins a cocoon for its pupa of a 

 conical shape, and closed at the lower end. 



Upon two occasions we have received speci- 

 mens of this larva from Mr. Green ; but each 

 time the water became so foul during the tran- 

 sit that the larvs soon perished, and we were 

 consequently unable to breed the perfect fly. 

 "While these larvae were in our possession, we 



made sundry observations on their peculiarities ; 

 but the article which follows, from Baron Osten 

 Sacken, on the transformations of the genus, is 

 so exhaustive, that we content ourselves with 

 presenting the life-like drawings at Figure 143. 

 The slight differences in form between our 

 figures of the pupa and those of Verdat may be 

 accounted for, either by a difference in species 

 or in maturity. "We will also premise that our 

 pupse, like "S^erdat's and Scheflfer's, had four 

 principal branches and eight tracheal filaments, 

 each side ; that the silk is spun from the mouth 

 (apparently from lower lip), and that the fan- 

 shaped organs either serve to spread the web- 

 nets, so as to entangle the animalcules which 

 form this insect's food, or, what is more prob- 

 able, serve, as do the cilise of many other small 

 animals, to form a vortex by the rotary motion of 

 the head observed by filr. Green ; and the animal- 

 cules, thus engulfed in this miniature maelstrom, 

 are irresistably drawn towards the mouth. 



Aside from its curious transformations, and 

 this newly-discovered destructive habit in the 

 larva state, this genus possesses an unusual 

 [Fig. 144.] interest from the fact that 



it furnishes the well known 

 Black-fly of the North, 

 and the celebratedBuFFALO- 

 GNAT of the Southwest ; and, 

 in order that the perfect 

 form may be recognized, we 

 Color-Black. present the annexed outline 



(Fig. 144, after Packard), of the former species, 

 Simulium molestum. 



"Where breeding ponds can be so protected as 

 to prevent these flies getting at the water dur- 

 ing the summer, it follows that the young fish 

 will not be troubled with the web of the larvse ; 

 but it is doubtful whether any such protection 

 can be given in the majority of oases. "We shall 

 be glad to publish any further observations on 

 the habits of these larvffi that may be made by 

 parties possessing the proper facilities for study, 

 and will add that, according to Osten Sacken, 

 besides this spinning larva of Simulium, that of 

 the genus Chironomus seems to weave the earthy 

 sheath in which it lives, and that of Tanypus 

 moves about in a light spun sheath, according 

 to Lyonnet. 



S^By a strange oversight we omitted the 

 name of Cjtus Thomas in our list of contributors 

 published last month. Mr. Thomas was, many 

 years ago, well known as a writer on Illinois 

 entomological subjects, and, knowing that he is 

 with us, heart and hand, in our work, we owe 

 liim an apology for this oversight, . 



