
THE METAMORPHOSIS OF SISYRA. 
MAUDE H. ANTHONY. 
Sisyra, like most of the Hemerobiida, is an insect of whose 
life history no thorough study has been made, and very little 
is known of either its habits or metamorphosis. It is an 
obscure little fly, chiefly interesting on account of some pecu- - 
liar structures of its larva. The larva has been known since 
Westwood described it in 1839, but it has never been reared 
until last summer, at the entomological field station at Saranac 
Inn, New York. It passes its larval existence as a parasite on 
fresh-water sponges, clinging to their surfaces or descending 
into the open osteoles, piercing the sponge tissue with its long 
decurved jaws. The food thus obtained is so pure as to be 
wholly absorbed, leaving no residuum. At least one-fourth of 
the posterior portion of the stomach is atrophied, leaving no 
opening from the stomach at that end. Carnivorous habits and 
piercing mouth parts are common to other hemerobian larve, 
but the decurved position of the mouth parts and the tracheal 
gills are peculiar alone to this insect and Climacia, its nearest 
ally, which is of similar habits. The singular adaptations of 
the mouth parts and alimentary tract to the nature of its food 
I shall describe in detail in this paper. 
The most remarkable structure of this larva is the silk- 
secreting apparatus. In general the silk glands of insects are 
metamorphosed salivary glands, but in the Sisyra larva they 
are a modification of the Malpighian tubules; and it seems 
probable that the nitrogen waste of the body is used, partially 
at least, in the manufacture of silk. This seems to be another 
remarkable instance of the economy of the by-product occurring 
in insect life. No such extensive modification of structure in 
adaptation to a peculiar environment has been described in any 
other insect ; but two near relatives of Sisyra, Osmylus and Myr- 
meleon, have a somewhat similar development of silk glands. 
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