276 



BULLETIN OF THE BUREAU OF FISHERIES. 



Head one-half longer than wide, strongly flattened, widest through the bases of the antennae, which 

 are attached near the anterior corners behind the bases of the mandibles. Sides of the head behind 

 the eyes contracted in a uniform curve to a short neck at the posterior margin. Behind each group of 

 eyes on the lateral margin is a tuft of silky hairs, and the curve from there to the neck is thickly set 

 with short spines, nine or ten in number. At the center of the anterior margin on the dorsal surface 

 is a short rounded rostrum, about one-quarter as wide as the head itself. The frontal border of this 

 rostrum has a fringe made up of two rows of rigid flattened processes similar to those on the larva of 

 LaccopMlus maculosus. In the present larva, however, the difference in the lengths of the processes 

 of the two rows is much greater, and in the ventral row of longer processes there are two lengths alter- 

 nating with each other. The rostrum is strongly arched dorsally and is flanked on either side by a 

 small projection tipped with three similar processes. 



The antennae are attached to the lateral margins behind the bases of the mandibles, are filiform 

 and four-jointed, the terminal joint minute. The mandibles are slender, bluntly pointed, and grooved 

 on the inner margin nearly to the base, which has a small tooth at its center on the dorsal surface. The 

 maxillae have a short and narrow cylindrical cardo and a much wider stipes, whose tip is covered with 

 short spines and whose inner margin is set with a dense fringe of short hairs, in the midst of which are 

 two long curved spines or claws. The galea is a short fingerlike process tipped with a single seta; the 

 paipifer is short, but the palp is long, filiform and three-jointed, the joints about the same length. The 

 labium is short and twice as wide as long, its terminal margin armed with short, blunt, cylindrical 

 processes. The labial palps are long and slender and two-jointed, the basal joint considerably longer 

 and stouter than the terminal, though both are almost filiform. The ligula is wanting. 



The legs are long and slender, with a fringe of short hairs. Each tracheal gill of the abdomen con- 

 tains a minute central tracheole, which is given off from the lateral trachea and is unbranched. From 

 its dorsal wall a short tube leads to the spiracle in the same segment, which is inoperative during the 

 larval stage. In the first segment the distance from the lateral trachea to the base of the spiracle tube 

 is considerable, but this distance diminishes in each successive segment and becomes very short in the 

 sixth segment. The spiracles on the seventh segment are ventral to the tracheae and are not visible 

 in dorsal view. 



The general color of the fully matured larva is yellow with a light tinge of brown. On the dorsal 

 surface of the head are two dark-brown spots, shaped together like the letter H, one on either side just 

 in front of the eyes. Behind each group of eyes is an irregular spot extending backward and inward 

 toward the mid line. The mandibles are brown, darker toward the tip; the center of the first joint of 

 the antennae is slightly darker in color, while the center of the second joint is almost black; the ends 

 of both joints are white. There is a dark-brown spot on either side of the neck at the base of the head, 

 a ring of brown around each joint of the legs, and a narrow band at the base of the cerci, with a wider 

 one at their tips. On the dorsal surface of each segment of the thorax and abdomen is a pair of sclerites 

 faintly marked in brown; on the eighth and ninth segments these are fused and extend around the 

 segment as in the LaccopMlus larva. 



Pupation. — When fully grown, the larva crawls out on the land and burrows into the earth from 

 three-quarters of an inch to an inch and a half below the surface. Here it hollows out a pupal chamber 

 10 to 12 mm. in diameter, and after resting from 24 to 48 hours it pupates. As soon as it comes out of 

 the water its spiracles begin to function and its lateral gills dry up and shrivel. Usually by the time 

 pupation begins most of them are broken off, and the larval skins found inside of the pupal chambers 

 seldom have more than one or two of them l^it still attached. 



Description of the pupa. — General form ovate, not much widened anteriorly, rather bluntly rounded 

 posteriorly. Total length, 6.75 mm. ; cerci, 2 mm. additional. Greatest width, at the second abdominal 

 segment, 3 mm. Color brownish-white except the eyes, which are black. 



The head is sunken deeply in the prothorax and has a row of five small styli in front of, and another 

 row of six behind each eye on the top of the head. The anterior and lateral margins of the pronotum 

 are densely fringed with similar styli, and there are about eight along the posterior margin at each corner. 

 The meso thorax and metathorax each have a group of five styli on either side of the mid line, and another 

 group of three at the base of each elytron and wing. Each of the first seven abdominal segments has a 

 group of from three to five styli on either side of the mid line and another group of two or three behind 

 each spiracle. The eighth segment has two on either side of the mid line and one on each lateral margin. 



At the posterior end of the abdomen are the pupal cerci, which are very slender, 2 mm. in length 

 and only one-seventh as wide at the base. 



