WATER BEETLES IN RELATION TO PONDFISH CULTURE. 



287 



swimmers in consequence. In the male the tarsi of the two front pairs of legs are 

 dilated and covered on the ventral surface with spongy hairs. There are also rows 

 of fine ridges on the plates of the hind coxae, which form a stridulating organ when 

 rubbed by the hind femora. Two species are common in the Fairport fishponds and a 

 third is found rarely. 



Laccophilus maculosus Say. Figures 20, 39, 41, 43, 44, 46, 48, 50. 



Laccophilus maculosus (Say, 1825, p. 100). 



Eggs. — No eggs of this species were obtained, but it is probable that they are inserted singly by the 

 female in the stems of water plants after the manner of other dytiscids. 



Habits of the larva. — The larvae are excellent swimmers, and when out of the water are much the 

 most agile of any larvae here described. The swimming fringes are well developed on all the legs and 

 carry the larva through the water without any movement of the body itself. The resultant motion is 

 rapid and exceptionally uniform, the abdomen and cerci being used for steering purposes only. When 

 out of the water, the body is considerably shortened by the telescoping of the segments, the abdomen 

 is lifted well above the surface of the ground on the long legs and inclined slightly upward, and the larva 

 walks with great rapidity or even runs and can turn and dodge with agility. 



Kept in an aquarium with plenty of water plants the larvae are quiet and do not show their cannibalis- 

 tic tendencies at once. They crawl about over the plants very slowly, feeling about with each foot before 

 putting it forward and keeping the abdomen elevated at an angle of 45°. They breathe by raising the 

 tip of the abdomen to the surface of the water while still standing on the plants, at the same time in- 

 clining the cerci ventrally until they rest upon the surface film. The two posterior spiracles are opened 

 in a manner similar to that in the Dytiscus larva. Having filled the air tubes, this larva can remain an 

 hour or more beneath the surface. In clear water they are obliged to swim to the surface in order to 

 breathe. In doing this the head is kept upward until close to the surface, then the tail is elevated in a 

 broad curve and an effort is made to throw the cerci out horizontally on top of the surface film. Often 

 several efforts are made before this is accomplished, but once successful the body is dropped into a verti- 

 cal position and hangs supported by the cerci. When the breathing is completed, the cerci are elevated 

 and the larva sinks beneath the water. 



If put in a dish of clear water, some of them betray cannibalistic tendencies by forthwith attacking 

 the others, and the one first grasped by the other's jaws gives up without a struggle, even when his head 

 is left free so that he could fight if he would. The victor then swims about sucking the juices of his 

 victim until they are all extracted, the empty skin being finally thrown away. 



In the ponds these larvae frequent the open water between the rush stems but do not take kindly 

 to Hydrodictyon or similar blanket algae. They do, however, crawl about among the Spirogyra and 

 Mougeotia and feed on the larvae usually found there — Corethra, Ceratopogon, Dixa, etc. — and occasion- 

 ally they eat a larva of Peltodytes, Haliplus, or Hydroporus, which are .found in the same localities. 



Description of the larva. — General form spindle-shaped, 7 to 9 mm. long, the body being widest 

 through the metathorax where it is 1 to 1.5 mm. broad, and tapering slightly forward and backward (fig. 

 20, opp. p. 275). The head is comparatively large, widest through the eyes, where it is the same width 

 as the thorax, and contracted posteriorly to less than half that width. The lateral margins behind the 

 eyes are armed with a row of five or six short and stout spines on either side. The prothorax is a trifle 

 longer than wide, the anterior margin half the width of the posterior, the sides strongly convex. The 

 mesothorax and metathorax each increase sUghtly in width, while the abdomen segments diminish 

 regularly, the last one being rather abruptly contracted posteriorly at the base of the cerci (fig. 20). 



The sclerite of the prothorax extends laterally nearly to the bases of the first legs ; those of the meso- 

 thorax and metathorax and the first five abdominal segments do not reach the lateral margins ; that of the 

 sixth abdominal segment extends onto the ventral surface, covering three-quarters of the entire circum- 

 ference, and those of the seventh and eighth segments extend around the body, covering the entire 

 surface, dorsal, lateral, and ventral. 



The abdominal segments are capable of considerable telescoping, and when the larva is taken out 

 of the water, or when it crawls out of its own accord, the body is much shortened by the pushing of the 

 anterior end of each segment into the posterior end of the segment in front of it. In preservatives also 

 the body of the larva is usually telescoped in the same manner, but occasionally it remains extended. 



