NORTH AMERICAX COLEOPTERA. 



15 



At this point I wish to assert positively that the abdominal spira- 

 cles, seven in number, are all situated in the connecting membrane, the 



last spiracle is concealed by the closing 

 together of the last dorsal and the last 

 visible ventral segments. Consequently 

 Pleocoma is a Laparostict Lamellicorn ! 

 In order that the position of the spi- 

 racles may be seen by those who do not 

 have a Pleocoma, much less a specimen 

 to dissect, I have had the accompany- 

 ing photographic block prepared from 

 a dissection spread between glass plates. 

 The photograi)hic method has reversed 

 tlie sides, this being the same prepara- 

 ti(m as that sketched on Plate II. The 

 ventral })orti()n is to the left. The small terminal segment is not 

 visible, excejjt by dissection, being completely retracted within the 

 abdomen. The accompanying figure is about two and a half times 

 the size of nature. 



The argument drawn from the oral organs by Gerstaecker seems 

 to me of but little value. Pleocoma, as already stated, has but a 

 brief existence, the mouth parts are reduced in size and so crowded 

 as to be of little use in taking food. As far as the mouth parts are 

 concerned Pleocoma differs no more from Bradycinetus (Athyreiis X 

 olim) than the latter does from Aphodius (pi. ii, figs. 6-16), and I 

 think there can be no doubt that these are equally Laparostict La- 

 mellicorns. Atrophy of the mouth parts is observed in more than 

 one family of Coleoptera and indicates, usually, a very ephemeral 

 life in the species. 



After having stated several times that Pleocoma is not a Lapa- 

 rostict, Gerstaecker discusses the question whether it should consti- 

 tute a distinct tribe. It is not necessary to follow his argument here 

 unless it be conceded that the position of the spiracles is Pleurostict, 

 then he may be right, otherwise wrong. 



Gerstaecker then discusses the structure of the antennae. It must 

 be admitted that these ai-e entirely anomalous for a Laparostict and 

 suggest the polyphyllous clubs of many of the i\Ielolonthid;e well 

 known to every one. This is, however, one of those instances abun- 

 dant everywhere in zoology in which an animal, with a fundamental 

 structure of some well recognized series, has a superadded peculiarity 

 possessed by sotue other gi-oup not otherwise related. 



