444 NEW YORK STATOB MUSEUM 



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

 panse 20 to 40 mm, hind wings somewhat less. 

 The males are usually a little smaller than 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 browu; abdominal seg- 



(^ p^ ments brown on the dorsal side and 



S^IIf^ somewhat on the ventral side; first 



seven segments of the abdomen car-li 



supplied with a pair of five jointed, 

 lateral appendages, evidently trach- 

 eal gills, each with two rows of deli- 

 Ccn^<u{.u cate hairs [fig. 20] ; within these 



thin, white walled, gill appendages 

 are seen finely divided trachea; from 

 the last abdominal segment is a 

 single caudal appendage similar to 

 ClcuJiy^dM ^ but longer than the lateral ones and 



Fig. so Bggsofsiaiididae not joiuted and supplied with tioo 



large branching trachea and ^owr 

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

 has suggested, that the caudal appendage 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 anteuna has five segments, but the basal 

 one if often obscure. 



On the dorsal side of the larva. ofS. infumata the segments 

 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 pulsations 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 species 

 in Europe, have been briefly described by Miall [1895] 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. infumata, have been found in 

 great numbers. They agree with the above description. The 

 " whitish projection," or micropylar projection, is not 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. 



