5 38 HEMIPTERA 



that entirely covers and conceals the alar organs, so that the 

 Insect has all the appearance of being apterous. The exact com- 

 position of the abdomen has not been satisfactorily determined, 

 opinions varying as to whether the segments are nine, ten, or 

 eleven in number. The difticulty of determining the point 

 is due to two facts : viz. the extreme modification of the terminal 

 segments in connection with the genital appendages, and the 

 prominence of the extremity of the alimentary canal. Tf this 

 terminal projection is to be treated as a segment, it would appear 

 that eleven segments exist, at any rate in some cases ; as the 

 writer has counted ten distinct segments in a young Coreid bug, 

 in addition to the terminal tube. This tulje in some of the male 

 Heteroptera is very subject to curious modifications, and has 

 been called the rectal cauda. Verhoeft' considers that ten seg- 

 ments were invariably present in the females examined by him 

 in various families of Heteroptera and Homoptera.^ In Aphidae 

 (a division of Homoptera), Balbiani considers there are eleven 

 abdominal segments present ; but he treats as a segment a pro- 

 jection, called the cauda, situate over the anus ; this structure does 

 not appear to be homologous with the rectal cauda we have just 

 mentioned. In Coccidae the number of abdominal segments is 

 apparently reduced. Schiodte states ""' that the older authorities 

 are correct in respect of the stigmata ; there are, he says, in 

 Heteroptera invarialjly ten pairs ; one for each thoracic segment ; 

 and seven abdominal, placed on the ventral face of the pleural 

 fold of the abdomen. In some cases there are additional orifices 

 on the external surface that have been taken for stigmata, though 

 they are really orifices of odoriferous glands ; these openings may 

 exist on the metasterna or on the dorsal surface of the abdomen. 

 The lateral margins of the abdomen are frequently greatly de- 

 veloped in Heteroptera, and are called " connexivum ; " the upper 

 and lower surfaces of the body meeting together far within the 

 marginal outline. Dr Anton Dohrn many years ago ^ called atten- 

 tion to the extremely remarkable structure of the terminal segments 

 in many male Hemiptera ; and the subject has been subsequently 

 very imperfectly treated liy the present writer and other ento- 

 mologists, luit it has never received the attention it deserves. 



Ent. Nachr. xix. 1893, p. 369. 

 - NaturUst. Tidskr. (3) vi. 1896 ; translated in Ann. X. BisL (4), vi. 1870, 

 p. 225. -i Ent. Zeit. Stettin, xxvii. 1866, p. 321. 



