THE HEMIPTEROUS GENUS BELOSTOMA. 61 



large quantity of the shells of Physa, Limnea, Spc, where Belostoma existed, to 

 which he attributed their destruction. 



They hold their prey with the fore legs, by folding it between the thighs and tibiae. 



Their bite is exceedingly venomous to the smaller animals, an insect dying in a 

 few seconds after a portion of saliva has been introduced with the oral set®. When 

 any one of them is held between the fore-finger and thumb, and irritated, it will 

 straighten the promuscus, and a small drop of pellucid liquor will be seen to appear 

 at the extremity. A portion of this fluid I took upon the poir t of a fine needle, and 

 with it punctured the thorax of a fly, which was followed by death in ten seconds. 

 The same experiment I repeated several times with the same result. Introduced 

 into the abdomen it did not operate so quickly. 



The puncture of Belostoma, which Dr. Griffith once experienced, he informed me, 

 produces much pain and inflammation. 



Belostoma and Perthostoma are capable of quitting the water, which they but 

 seldom do, unless their situation is nearly dried up, or is depopulated through their 

 voracious appetite, when they fly by night to some other neighbouring and more 

 convenient water. 



The female of Nepa, including Belostoma, according to most authors, deposites her 

 eorgs in the soft stems of aquatic plants. 



The female of Perthostoma carries her eggs upon her back, until the larvae are 

 nearly ready to escape. The mass of eggs which she thus conveys about with her, I 

 found generally to amount to about 130, and at one period to be one and a half times 

 her own weight. They are ranged regularly side by side, and are cemented to each 

 other and to the elytra, by a bassorine-like substance insoluble in water. "When the 

 ova have arrived at maturity, the insect casts the mass from her back, when they lie 

 at the bottom of the water until the young escape. How she ever manages to get 

 them in such a novel situation, I am unable to say ; I could not detect anything in 

 the anatomical arrangement of the genitalia to explain it, and the caudal setae if used 

 as an ovipositor, could not extend one-fourth the necessary distance. Stoll (Punaisses 

 de Stoll, p. 36, tab. 7, fig. 6,) has represented Perthostoma? cinerea, (Nepa) with a 

 similar mass of ova upon the back, which he has mistaken for the ova of an aquatic 

 mite. The Nepadse are infested by a species of Hydrachna, but the ova of this are 

 comparatively small, of a yellow colour, and are attached by a narrow pedicle 

 irregularly upon any part of the inferior surface of the animal. Beauvois (Ins. rec. 

 en Afrique et en Amerique, PI. 20. fig. 3,) has represented P. ? siibspinosa (Nepa,) 

 with a mass of ova upon its back, which he correctly attributes to the animal. I am 

 well convinced that such is the case, having seen the larvae escape from the ova, and 

 also find that the ovaries of the female are empty when the ova are upon her back. 



The ova are oval in form, of an ash colour, and have an operculum-like hilum at 



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