464 COLEOPTERA. 



the prothorax, and the eleven-jointed antennae are insertea 

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

 nence. 



Dasctllid^ 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 larvic are 

 either like those of the Scarabwidce ^ being provided with 

 short fonr-jointed antennae, and without ocelli, as in Atop(i ; or 

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

 tennne and very well developed limbs, as in Cuphon. The genus 

 Prionocuplwn has the first joint of the antennte 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 PrionocyphoR discoideus Sa}^ as being- 

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

 Ir.teral edges, the body slightly attenuated before and behind, 

 of a leathery consistence, dull pale 3'ellowish, and four-tenths 

 of an inch in length. It was found by Mr. Walsh in the hol- 

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

 vigorously up and dow^n a pencil of hairs proceeding from a 

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

 pairs of filaments, each beautifully 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. Generall}', when it is beneath the surface, the anal pencil 

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

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

 remarkably long antennae are constantly vibrating, like those 

 of terrestrial insects. The pupa is Avhite, with 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 arc about two-thirds 



