366 



THE AMEEICAN 



found a few sickly attenuated looking ones 

 adhering to stones in the bottom of the creek. 

 About the first of June I found immense num- 

 bers, both of larvffl and pupas, attached to water 

 plants that were three or four inches below the 

 surface of the water. 



I also found them on different^ occasions iu 

 vast quantities in several similar situations. A 

 great many were displaced by a heavy rain 

 storm, and carried on by the current of the 

 stream, until they found a resting place on 

 sunken boards and stones. The natural position 

 of the larviB iu the stream is a few inches below 

 the surface of the]watcr and iu the current of 

 the stream. Here the "wonderful instinct" of 

 the parent is exemplified; for if these larvcs 

 were near the bank, or where the temperature 

 of the stream varies, they would immediately 

 perish. Before they were disturbed they were 

 all attached to decaying vegetation, principally 

 water-cress. Some were on forest leaves of last 

 year's growth that had become entangled among 

 the water-cress. These leaves were of a brown 

 color, and^^^the larv;e on them were the same 

 color, while those on the leaves and stalks of the 

 water-cress were a murky green. But when 

 found on stones gr kept in a glass dish of clear 

 water for a time they are almost transparent. 

 The markings of black on the segments being 

 well defined. On account of the diflference in 

 color I inferred that they derived their nourish- 

 ment from the vegetation,[and^ while it was in a 

 state of decomposition. 



When frightened^they drop into the water, 

 suspended to the substance to which they had 

 been attached by means of a fine delicate thread, 

 in a similar manner to^many land larvse. They 

 can ascend this thiead, but it is very easily 

 broken by the action of the water and washed 



The pupsB,[;as well_as larvse, perish iu water 

 of a temperature warmer ^tliau that of the 

 stream. From this, we may infer, that this 

 particular species will.ouly be found at spring- 

 heads where the water 'remains of an even 

 temperature. 



I was enabled to obtain the perfect insect by 

 keeping pupaj in a^covered box in the current of 

 the stream. A day or two previous to emerging 

 from the water, the pupa looseusltself from the 

 case or "pouch" by a gentle wriggling motion 

 from side to side.'' When itbecomes free it rises 

 to the surface^of the water,'^ and^the fly gradu- 

 ally draws itself out of a^slit the_entire length 

 of the^pupa.^The legs are^the last to appear. 

 The fly rests on the surface of the water until 

 its wings expand and dry. This process usually 



takes a minute of time — sometimes more or 

 less. They leave the water just before sunset, 

 and will then be found flying among low herb- 

 age near the bank of the stream. In creeping 

 over my hands they caused a disagreeable tick- 

 ling sensation, apparently deriving their nour- 

 ishment in the same manner as the common 

 House-fly. 



There were a few larva marked with red on 

 the segments instead of the usual black. The 

 same red showed on the wings of the pupa and 

 in circular bands on the body and legs of the 

 imago. The larva spins, what has thus far been 

 called the " web;" in the center of this it then, 

 by working with its head bent backward over 

 its body, flnishes the pouch. The feathery orna- 

 ments on the head of the larvss seem to change 

 during the transformation into the fllameuts of 

 the pupas; the puparium being formed at the 

 same time by the contraction of the larva skin. 



There have been a succession of broods this 

 summer. During the warm season, a period of 

 two months elapsed between the egg and per- 

 fect forms. They were a week or ten days as 

 eggs, four weeks as larvae, and about three 

 weeks as pupae. These flies were much smaller 

 than those that appeared late in the season and 

 early iu the spring, although there was appar- 

 ently no difference in the size of the larvse and 

 pupse. At the present time, (Oct. 18th) there 

 are large quantities of minute larvse ou the 

 leaves of the water-cress. 



How or in what manner this larvse has come 

 to be designated as a "web worm," is more 

 than I can determine, as it spins no web either 

 for its own protection or for the destruction of 

 any living thing. There is only the single flla- 

 ment that suspends it iu the water when dis- 

 turbed, and the moorings of the pupa pouch. 

 These are all it ever spins. The only way it can 

 interfere with young trout is by supplying them 

 with a large amount of very palatable food. 



The following is quoted from Wilkes' Spirit 

 of the Times, (June 18) where this larvae is 

 called a submarine spider, and by a great natu- 

 ralist: 



" The ponds are owned by Mr. Myi-on Pardee, 

 a very wealthy gentleman of Oswego, who 

 pi'opagates trout for his amusement and scien- 

 tific purposes, he being a great naturalist. We 

 are informed that it is to Mr. Pardee that Seth 

 Green is indebted for the discovery of the sub- 

 marine spider and its web, so fatal to young 

 trout." 



Sara J. McBrdde. 



MUMFOKD, N, T., Oct. 19th, 1870. 



[We really hope that those who have the op- 

 portunity will sift this matter to the bottom, and 



