464 COLEOPTERA. 



the prothorax, and the eleven-jointed antennae are insertoa 

 immediately in front of the eyes, under a slight promi- 

 nence. 



Dasctllid.e Guerin. This group embraces genera differ- 

 ing much from each other ; the head is usually bent down, 

 sometimes prominent ; the antennae are eleven-jointed, distant 

 at their insertion immediately in front of the eyes, being 

 placed under a slight ridge, and the mandibles are not promi- 

 nent. They all live on aquatic plants, and the larva? are 

 either like those of the Scarabo'idce, being provided with 

 short four-jointed antenna;, and without ocelli, as in Atoiw ; or 

 they are long, ovate, with distinct ocelli, long bristle-like an- 

 tennae and very well developed limbs, as in Cyphon. The genus 

 Prionocyplwn has the first joint of the antennie much dilated, 

 and the joint of the labial palpi is inserted on the side of the 

 second ; in Cyphon the palpi are normal. Baron Osten Sacken 

 describes the larva of Prionocyplion discoideus Sa}^ as being 

 long, flattened ovate, like a sow-bug (Oniscus) with sharp 

 lateral edges, the body slightly attenuated before and behind, 

 of a leathery consistence, dull pale yellowish, and four-tenths 

 of an inch in length. It was found b}^ Mr. Walsh in the hol- 

 low of an oak stump filled with Avater, in which it " vibrated 

 vigorously up and down a pencil of hairs proceeding from a 

 horizontal slit in the tail ; this pencil is composed of three 

 pairs of filaments, each beautifull3' bipectinate. "When at the 

 surface this larva generally, but not always, swims on its back, 

 keeping its body slightly below the surface, and striking with 

 its feet, so as to jerk from point to point, in a curved line. The 

 pencil of hairs touches the surface all the time. "Occasion- 

 ally, says Mr. Walsh, "a bubble of air is discharged from the 

 tail. Generally, when it is beneath the surface, the anal pencil 

 ^s retracted entirely. It has the power of jerking its body sud- 

 denly round, and darting up and down with great Aigor. Its 

 remarkably long antennae are constantly vibrating, like those 

 of terrestrial insects. The pupa is white, v;ith large black 

 eyes which are very conspicuous beneath, and two short black 

 setae on the occiput. The body is covered with a short, white, 

 erect down or pubescence. The antennae are about two-thirds 



