102 [Assembly 



one or t"wo inches in thickness, and extending thirty yards in length. 

 Individually they are but about five lines long and a third of a line 

 in diameter. M. Guerin-Meneville has given interesting details of 

 some of these assemblies observed by him, as quoted in Figuier's 

 Insect World, pp. 46, 47. » 



That some of the species of the genus ma}' possess injurious 

 habits appears from the mention by Prof. Westwood, that Olivier 

 liad reared three species of Sciara from wheat, of which account is 

 given in Prem, Mhn. sur quelques Insectesqui attaquent les Ctrtdles^ 

 Paris, 1813. 



Sclari pyri, of Europe, is said to injure the blossoms and fruit 

 of the pear, causing them to fall ; while of other European species, 

 S. fucata lives in decaying potatoes, turnips and -other vegetables; 

 S. quinquelineata breeds in diseased potatoes and is supposed, by 

 some, to cause the " scab;" 8. tilicola produces a gall on the leaves 

 of young linden trees ; and S. Giraudii has been bred from stems 

 of Malva and Althcea. 



One of our American species, at least, is known to be injurious, 

 viz, Sciari nnali (Fitch), the larvte of which destroy the interior of 

 apples by burrowing through them, while the fair exterior shows no 

 indication of the concealed attack, {ist and Id Report Insects N. T., 

 p. 254.) 



Helophilus similis Macquart. 



From Dr. R, H. Morey, of old Chatham, Columbia county N. Y. 

 seven examples of the larva of one of the flower-flies {Syiq^Jiidce), 

 of the group known from their long anal ajjpendage as '' rat-tailed 

 larvae, '' which he had taken from a watering-trough at North Adams, 

 Massachusetts, were received on the 5th of July. He had previously 

 given me, on Jul}' 2nd, two examples of the same, taken from many 

 that were seen by him at that time. Upon his second visit to tlie 

 place, for additional specimens, only the above seven examples could 

 be obtained. Most of them had evidently left the trough and sought 

 other quarters for pupation. 



The larvae were placed in a glass of water with an inch of ground 

 and dead vegetable matter at the bottom. Thev hid themselves in 

 the ground, with their tail extended upward to the surface for res- 

 piration, to an extent of two inches, except when disturbed, when the 

 respiratory organ would be withdrawn from the surface and partly 

 contracted. 



Within the following week, some of the larvae were found float- 

 ing upon the surface of the water. As this condition was believed 

 to indicate approaching pupation, they were transferred to a box of 

 dampened saw-dust, into which tliey buried themselves. 



At this time they presented the following features : The body, 

 subcjdindrical, narrowing somewhat anteriorly, and one-half of an 

 inch in length by one-eighth of an inch broad ; beneath, Avhitish, 

 pale brown above, becoming darker toward the tail ; the several seg- 

 ments show six divisions (as wrinkles or folds) above, of which the 



