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BULLETIN OF THE BUREAU OF FISHERIES. 



The femora of the second legs are armed on the posterior margins with long conspicuous setae, in- 

 creasing in length towards the tip. The coxae of the third legs are large, the spurs at the tips of the 

 tibise are unequal and distinctly emarginate, the tarsi are armed with long swimming setae, and the 

 claws at their tips are unequal. 



Thermonectes ornaticollis (Aube). Figs. 53, 56, 59, 61, 63, 66, 68, 71, 74, 147, 148. 



Dytiscus ornaticollis (Aube, 1838, p. 140). 

 Thermonectes ornaticollis (Sharp, 1882, p. 678). 

 ^^^s.— The eggs of this species are probably deposited singly in the stems of water plants like those 

 of the preceding species. 



Habits of the larva.— It swims usually with a uniform motion and fair rapidity, but without any 

 movement of the body. When disturbed, however, it snaps its body like the basilaris larva by suddenly 

 lashing the last two segments of the abdomen against the water. This ability to jump or snap the body 

 is retained after the larva comes out of the water, and even after it is inside of the pupal chamber. If an 

 attempt is made to pick up such a larva, it will sometimes jump 8 or 10 inches in this manner. Its 

 breathing habits are similar to those already described for the preceding species. 



In the pond it swims about close to the surface and snaps up the copepods and Entomostraca that 

 swarm there. It frequently seizes small objects floating on the surface and draws them beneath the 

 water. After testing them in its mandibles it rejects those that are unfit for food and retains the others. 

 In an aquarium it eats mayfly larvae, is very fond of the larvae of both species of Tropistemus, and is able 

 to kill them when they are fully as large as itself. As both species of Tropistemus are abundant m the 

 ponds from which the Thermonectes larvae were taken it is probable that they constitute at least a 

 portion of the regular food of the latter. After it has killed its prey it usually swims to the siirface and 

 hangs from the surface film by means of its cerci, breathing and sucking the juices of its victim. It is 

 much the most graceful and beautifully colored larva of any here described. It is easily recognized, la 

 harmless, and furnishes good fish food. 



Description of the larva.— The general structure is the same as that of the hasilans larva, but the 

 following differences may be noted. Its total length, including the posterior cerci, is 22 mm., its greatest 

 width is 3.5 mm. In color the dorsal surface of the head and neck is yellow, with the following black 

 markings: The tips of the antenna and maxillary palps; the bases of the maxillae and mandibles; two 

 circular spots close together, one on either side of the mid line, near the anterior margin of the head 

 another pair of triangular spots behind the eyes, fused on the mid line, with a wide band extending from 

 the side of each to the lateral margin of the head behind the eyes; the entire eye areas; a semicircular 

 spot on either side of the neck behind the head. The dorsal surface of the thorax and abdomen is light 

 yellowish-brown, the sclerites narrowly edged with black, with a secondary edging on the lateral margins 

 inside of the first. Inside of this row of secondary edgings is a longitudinal stripe of dark brown, con- 

 necting anteriorly with the black line on the lateral margin of the head and running the whole length of 

 the body. There is another dark brown stripe on either side close to the mid line; along the mid line 

 and between the stripes are bands of light yellowish-brown. 



The terminal joint of the antenna is relatively larger than in the basilaris larva; the mandibles have 

 a fringe of hairs on the outer margin near the base and a row of fine teeth in the groove near the tip. 

 The maxillae are similar with a fringe of long hairs along the outer margin and the addition of a dense 

 covering of spines and hairs over the inner half of the basal portion. The labial palps are armed with 

 short spines on the outer distal margin of the basal joint and on the outer margin of the terminal jomt 

 near the base and at the tip. The inner margins of the terminal joints are sinuate for their distal half. 

 The ligula is relatively shorter than in the preceding species, but the two-jointed spmes at its tip are 

 longer, being fully as long as the ligula itself. 



Two of the eyes— the dorsal members of the anterior and middle pairs— are much larger than the 

 others are reddish in color, and protrude strongly from the surface of the head. The posterior pair are 

 much smaller and are close together on the lateral surface of the head, only the dorsal member of the 

 pair being visible from above. The ventral members of the first two pairs are on the ventral surface 

 of the head and are separated from the dorsal members by wide intervals, the space between the two 

 members of the middle pair being fully four-fifths of the thickness of the head. None of these last four 

 eyes project at all from the surface of the head. The underlying pigment of the two larger eyes is not 

 confined to the surface immediately beneath the skin but penetrates downwards and backwards nearly 



