56 INSECTS AT HOME. 



fingers out of tiie way of its jaws, he finds himself suddenly 

 and smartly wounded, as the Beetle struggles to regain its 

 liberty. The fact is, the insect, led by some strange and un- 

 accountable instinct, always retrogrades when seized in the 

 hand, and so inflicts a rather unpleasant wound with the ends 

 of this appendage. Whether or not it knows of the presence 

 of the weapon, and the use to which it is put, is of course im- 

 possible to say ; but that the insect can use its forked dagger as 

 well as if it were thoroughly acquainted with it, any of my 

 readers can easily test for himself by going to the nearest pond 

 and catching a Dyticus. Other Water Beetles possess the 

 forked appendage ; but it takes different shapes in different 

 species, and is exceedingly useful to entomologists, by enabling 

 them to decide upon the species when other marks fail them. 



This is, by the way, not the only weapon which the Dyticidse 

 possess. Like the Carabidse, and some other Geodephaga, 

 they exude a fluid of a singularly unpleasant smell when they 

 are captured ; but the liquid in question is white, and not black 

 like that of the Carabidse. At Fig. b is shown the maxilla and 

 palpi of the Dyticus, and d are the labial palpi. 



As the two sexes are so dissimilar in appearance, it will be 

 necessary to describe them separately. The colour of the male 

 Beetle is dim black, with the margins of the elytra marked with 

 a yellowish streak, narrow towards the apex, and widening 

 considerably towards and on the shoulders. It is in consequence 

 of this streak that the Beetle has received the specific name of 

 marginalis. The elytra are very smooth, with the exception 

 of three rows of punctures on the disc. There is a reddish- 

 yellow triangular mark on the forehead, and a very slight ridge 

 on the crown. The thorax is blacker than the elytra, and, like 

 them, has the margin yellow. 



The legs of this Beetle are excellent examples of these limbs 

 as they are modified in the Hydradephaga. Both the middle 

 and hind pairs of legs are flattened, oar-like, and furnished 

 with the bristle blade, and the coxa is so made that it only 

 allows one kind of movement to the limb. In consequence of 

 this peculiarity the Dyticus cannot walk properly, but only 

 scrambles about ; and if it should by chance fall on its back on 

 a smooth surface, it spins round and round in a most ludicrous 

 fashion. 



