DESCRIPTIONS OF GENERA AND SPECIES. 



207 



albuminoid contents of the capsule. The nymph now 

 passes into the hypopial stage, in which it can endure 

 greater changes of temperature, etc., than in any other, 

 and can attach itself firmly to insects and other 

 creatures. The empty capsule breaks and frees the 

 Hypopus, which avails itself of its power of fastening 

 on to other creatures in order to obtain a conveyance 

 to a fresh capsule ; it then leaves the temporary host, 

 mounts upon the new capsule, casts the hypopial skin, 

 becoming a fully grown nymph of the ordinary sort ; 

 which penetrates through the wall of the capsule, and 

 assumes the adult form inside. There reproduction 

 takes place, and the life-circle commences anew. The 

 author thinks that the nymph uses its short powerful 

 front legs to dig through the wall of the capsule ; but 

 I do not gather that he has seen the process : it is 

 quite probable that these legs may assist in opening 

 the slit when it is made, but I cannot help thinking 

 that the saw -like mandibles must be the real penetrat- 

 ing organs. 



That the genus has not been found out of Europe is 

 probably due to want of search. 



Table for the Identification of British Species of His- 



tiostoma. 



With mammil- 

 liform eleva- 

 tions, or tuber- * 

 cles, on dorsal 

 surface. 



Spines on noto- 

 gaster round 

 in section and 

 of the ordinary 

 character. 



Spines on noto-1 

 gaster short, less 

 than one tenth of 

 the length of the 

 abdomen. 

 Spines on noto-i 

 gaster longer 

 than abdomen. 



Principal spines on notogaster of' 

 male broad and ensiform, not 

 quite round in section near the 

 body. 



Without mammilliform elevations, or tubercles, on 

 dorsal surface 



H. ROSTRO-SER- 

 RATUM. 



H. SPINIPERUM. 



H. PULCHRUM. 



H. PYRIFORME. 



