AMERICAN COLEOPTERA. 99 



In every dissection I have made the three parts have always been 

 present, sometimes however very closely united and corneous - as in 

 Helluomorpha 103. It seems unprofitable to discuss the modifications 

 of the ligula and paraglossae, their forms are shown in the figures and 

 the explanations given in the tribal headings. 



From my own observations I think the labium the most unsafe and 

 unsatisfactory organ that can be made use of in classification and the 

 poor results to be obtained from it need no further illustration than 

 Lacordaire's system of Carabidae. When the labium is used in the 

 division of tribes into smaller gToups and genera we have a microscopic 

 subdivision resulting which overwhelms the science in a chaos of inde- 

 finable groups and an infinity of genera which threatens the exhaustion 

 of the capacity of the classic languages for further combination. 



A great part of the trouble with this organ seems to have resulted 

 from causes which Jacquelin Duval so well describes, (Gen. Col. Eur. i, 

 p. 34, note). When observed under varying external conditions the 

 paraglossae present rather diverse forms. They are often thin and 

 membranous and will contract and expand with moisture and fail to 

 present the same appearance when dry as when wet. My own dissections 

 have been drawn while the specimens were moist, and in the smaller 

 ones, enclosed in a drop of water. 



The appendages of the ligula, the terminal setfie of varying number, 

 seem useful in assisting the placing of genera when properly subordinated 

 to other characters, but I think that genera based solely on the number 

 of these setae or their position must ultimately fail of recognition. 



While I do not believe the ligula to possess the value assigned by 

 some authors it may be made useful. In some vast groujis like the 

 Pterostichini and Platynini there is a similarity of type which 

 one will readily recognize. There are however important modifications 

 that need riot mislead if properly studied, Leati'gnafhus 65, is one of 

 these. In this the ligula and paraglossae are both well marked, the 

 former feebly corneous, the latter slender and long but connected with 

 the central ligula by a transparent membrane which serves to add strength 

 to the organ which is at best very weak and thin. 



Labial Palpi. — These organs are usually similar in their terminal 

 joint to the maxillary palpi, when they differ it affords a very useful 

 means of separating genera. It appears however to have escaped notice 

 that the relative length of the last two joints to each other is a matter 

 of fir greater importance than has been recognized. The terminal joint 

 may be e([ua\ to or longer than the preceding, or shorter. In the former 



