June, 1911.] Severin-Severin : Habits of Belostoma and Nepa. 103 



This predaceous water-bug feeds upon a variety of animals found 

 in its environment. The aquatic insects most abundantly captured, as 

 revealed in our aquaria, were the back-swimmers and water-boatmen. 

 According to Weed's (39, pp. 11-12) observations, the most im- 

 portant element of food as noticed in his aquaria, " consisted of the 

 larvce and nymphs of dragon-flies (Libellulidse). The next most 

 abundant victim was the common undulating back-swimmer (Noto- 

 nccta nndulata). . . . Univalve snails also occasionally contribute to 

 the diet of this insatiable creature, as one was observed feeding upon 

 a small snail with a spiral shell. May-fly larvae (Ephemeridse) also 

 sucks out the juices of its own kind. On rare occasions we observed 

 (10, p. 191), however, noticed that Belostoma often seizes and 

 form part of its food, as was shown by similar observations." Bueno 

 a mature form of this bug with its piercing organs penetrating 

 the soft chitin and sucking out the juices of a Belostoma which 

 had recently moulted and become full grown. While the older 

 mature individuals will live together for a long time, rarely devour- 

 ing one another, they will attack and suck out the juices of their own 

 young. If young Belostomas of different sizes are placed in an 

 aquarium, the smaller ones will be exterminated in a short time. 



Nepa is also carnivorous. It will reach for its prey with its 

 raptorial legs, but in no instance could this aquatic bug be induced to 

 swim or run after its prey. If a house-fly or a dragon-fly nymph 

 is carefully and slowly brought towards the front legs, the claw-like 

 tibiae and tarsi slowly move away from the femora. If they are 

 already extended and well separated, as is often the case, the insect 

 usually remains perfectly quiet vmtil the prey is actually placed be- 

 tween the outstretched legs, when suddenly it is seized and securely 

 held. The piercing-organs are then inserted into a soft part of the 

 body and the insect begins to feed. It will also grasp the tip of a 

 pencil when this is slowly and carefully placed between the out- 

 stretched front legs. If, however, a fly, dragon-fly nymph or a pencil 

 is quickly and suddenly presented to the hemipteron, it will usually 

 draw back its front legs, folding the tibia and tarsus back into the 

 groove of the femur. 



Nepa will not only use smaller animals than itself as food, but it 

 will also feed upon dragon-fly nymphs considerably larger and 



