366 



THE AMERICAN 



found a few sickly attenuated lookiuj? oues 

 adhering to stones iu tlie bottom of the creek. 

 About the first of June I found immeuse num- 

 bers, both of larva? and pupa;, attached to water 

 plants that were, three or four inches below the 

 surface of the water. 



I also found them on different,, occasions in 

 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 lai-viB in the stream is a few inches below 

 the surface of the]'wator and iu the current of 

 the stream. Here the " wonderful instinct" of 

 the parent is exemplified; for if these larvae 

 were near the bank, or where the temijcrature 

 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 liad become eutangled among 

 the water-cress. These leaves were of a brown 

 color, and.^the larvic on thcm~were the same 

 color, while those on the leaves and stalks of the 

 water-cress were a murky green. But when 

 found on stones or 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 diflerence in 

 color I inferred that they derived their nourish- 

 ment from the vegetalioii,'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 larvas. They 

 can ascend this thread, but it is very easily 

 broken by the action of the water and washed 

 away. 



The pupiB,>s wcll_as larvse, perish in water 

 of a temperature warmer .^thau that of the 

 stream. From this, we may infer, that this 

 particular species will.only be found at spring- 

 heads where the water remains of an even 

 temperature. 



I was enabled to obtain the perfect insect by 

 keeping pup;e iu a^covered box iu the current o* 

 the stream. A day or two previous to emerging 

 from the water, the pupa looseus'..itself from the 

 case or " pouch" by a gentle wriggling motion 

 from side to side." When it^becomes free it rises 

 to the surface of the_water,'aud the fly gradu- 

 ally draws itself out of a slit the_entire length 

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

 The fly rests on the surface of the water until 

 its wings expand and dry. Tliis 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 

 Ilouse-fly. 



There were a few larvae 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, finishes the pouch. The feathery orna- 

 ments on the head of the larvae seem to change 

 during the transformation into the filaments 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 mouths 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 iu the season and 

 early in the spi-ing, altliough there was appar- 

 ently no difference in the size of the larvaj and 

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

 are large quantities of minute larvae ou the 

 leaves of the water-cress. 



IIow or in what manner this larvae 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 fila- 

 ment that suspends it in the water when dis- 

 turbed, and the moorings of the pupa pouch. 

 These are all it ever spins. The ouly 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' Sinrit 

 of the Times, (June 18) where tliis larvse is 

 called a submarine spider, and by a great natu- 

 ralist: 



" The ponds are owned by Mr. Myron Pardee, 

 a very wealthy gentleman of Oswego, who 

 propagates 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. McBride. 



MUMPORD, N, Y., Oct. loth, 1870. 



[We really hope that those who have the op- 

 portunity will sift this matter to the bottom, and 



