308 



BULLETI1S3" OF THE BUREAU OF FISHERIES. 



strongly bronzed; beneath black very shining; abdomen tinged with brown; legs brownish-yellow. 

 Elytra of the male feebly sinuate both on the lateral margins and near the tips, the latter separated but 

 little and the angles only slightly produced backwards. In the female both sinuations are more pro- 

 nounced, the tips are more widely separated, and the angles are more distinctly produced. 



The antennae are peculiar and are very similar to those of Gyrinus, which are usually cited by 

 authors as the type of what is known as the irregular form. Each antenna is made up of two parts, a 

 proximal portion of three joints and a distal portion of seven joints. The second proximal joint is 

 produced into a wide wing, which curves up around the base of the distal portion of the antenna. To 

 the inside of this wing is attached the third proximal joint, and the fixst distal joint is fastened by a 

 minute neck to the dorsal surface of this third joint. The distal portion of the antenna is club-shaped 

 and six-jointed, the first joint apparently made up of three joints fused. Miall (1895, p. 34) said: "The 

 peculiar form of the Gyrinus antenna is probably a means of keeping it dry." In this antenna the 

 enveloping wing of the second proximal joint and the long fringes of hairs on the third joint assist in 

 keeping the sensory terminal portion dry. 



The mandibles are large and strong but are blunt and approach the herbivorous type more closely 

 than the carnivorous. The maxillae are sharp and sickle-shaped and typically carnivorous; the palp 

 is five- jointed and somewhat club-shaped. The labium is well developed, with large circular para- 

 glossse and three- jointed palps. 



The fore legs are prehensile, and in the male the tarsal joints are slightly dilated and their ventral 

 surface is covered with rows of suckers that stand out like the pile on velvet. Each sucker is a narrow 

 tube enlarged at the tip into a cup-shaped disk. 



Genus GYRINUS Geoffroy. 



Gyrinus (Linnaeus, 1758, p. 412). 

 Gyrinus (Geoffroy, 1762, p. 193). 



This is a genus whose species are smaller, narrower, and more convex than 

 those of the preceding genus. Each elytron has 11 rows of distinct punctures and 

 when held so as to reflect the light usually shows a yellowish tint. The legs vary 

 from yellow to reddish-brown in color and are relatively longer than in the genus 

 Dineutes. The species vary so little that they are hard to distinguish; four have 

 been reported from the fishponds but are not found there regularly. They seem 

 rather to be itinerant visitors from the river and occur most frequently on the 

 ponds that are nearest the river. 



Gyrinus ventralis Kirby, 1837, p. 80. 

 Gyrinus limbatus Say, 1825, p. 109. 



Neither of these species breeds in the Fairport fishponds, but the adults are 

 occasionally found there in considerable numbers, and hence the more important 

 facts in their life history will be of interest. These facts are taken from various 

 authors and apply equally to the two species. 



Eggs. — The eggs are laid in rows on the leaves or stems of water plants and closely resemble those 

 of the preceding genus in shape, in color, and in time of hatching. 



Habits of the larva. — It swims and breathes in the same manner as the larva of Dineutes aheady 

 described. According to Miall (1895, p. 39) : "The Gyrinus larva feeds upon water insects and possibly 

 upon other aquatic animals. Failing these it will eat the tender parts of submerged plants. ' ' Accord- 

 ing to Needham the larvae also "feed upon the body fluids of bloodworms and other small animal prey " 

 (1916, p. 221). It is diflficult to understand how a larva like this, whose mouth parts are typically 

 carnivorous, and whose mandibles are suctorial like those of the Dytiscidse, can eat vegetable food aa 

 stated by Miall. 



Description of the larva. — This larva is similar to that of Dineutes, except that the first two pairs 

 of lateral gills are fringed with hairs like the other pairs. This larva is only about 14 mm. in length 

 and is widest through the second thoracic segment, which is nearly 2 mm. in width. The abdomen 



