444 



NEW YORK STATE MUSEUM 



tennae filiform, about equal to the body in lengtli; wing ex- 

 panse 20 to 40 mm, liind wings somewhat less. 



The males are usually a little smaller t4ian the females. 



Larva. Suited for aquatic life. 20 to 30 mm long when full 



grown; tapering from head to the caudal end of abdomen; head 



and thorax yellow on dorsal side, mesothorax and metathorax 



bearing some light brown markings; the appendages of the head 



and the eyes brown; abdominal seg- 

 ments brown on the dorsal side and 

 somewhat on the ventral side; first 

 seven segments of the abdomen i'a<-h 

 supplied with a pair of five jointed, 

 lateral appendages, evidently trach- 

 eal gills, each with two rows of deli- 

 cate hairs [fig. '20] ; within these 

 thin, white walU'd. gill a])p("ndage* 

 are seen finely divided trachea; from 

 Ihe last abdominal segment is a 



cz> 



Sa^Cl^aS 



\^crr^(LoX4L4 



single cauilal apj^'udage similar to 



Fig. '20 Eggs Of Slalidldae 



but longer than the lateral ones and 

 not jointed and su]>])li('d with tiro 

 large branching trachea and four 

 rows of delicate hairs. This structure may indicate, as Miall 

 has suggested, that the caudal ajipendage may have been 

 formed by the fusion of two lateral appendages. There is a 

 pair of minute spiracles present on each abdominal segment 

 except the last. Each antenna has five segments, but the basal 

 one if often obscure. 



On the dorsal side of the larva of S. i n f u m a t a the segmeuts^ 

 are translucent, often showing the viscera. The lateral lobes 

 of the abdominal segments are so transparent that the particles 

 of blood may be seen and the pulsations of the heart may be 

 counted. I found the number of jmlsations to vary somewhat,, 

 but the average is about 10 a minute. Oenocytes with the finest 

 branches of tracheoles leading to them are so plainly visible that 

 they can be photographed. 



Eggs. The eggs of S. 1 u t a r i a , the most common specie* 

 in Europe, have been briefly d<'scribed by Miall [1S05] as " dark 

 brown, several hundred in one cluster, cylindrical with rounded 

 ends, and closely packed together; from the free end of each egg 

 a small, pointed and whitish projection is given off." The eggs 

 of our most common species, S. i n f u m a t a , have been found in 

 great numbers. They agree with the above description. The 

 " whitish projection," or microi>ylar ])rojection, is nut knobbed 

 at the end, but the distal portion, which may be the micropylar 

 surface, is cylindric in form, with a short, narrow pedicel at the 

 point of attachment to the eggshell. 



