32 
BRITISH BEETLES. 
Labium of Piero* tiehus niger. 
d 3 , the lacinia or blade; d\ the palpifer ; dl’, the stipes 
or stalk, and d °, the cardo, base, hinge, or insertion, by 
which the lower jaw is attached to the inner side of the 
head. There are two small 
organs, the paraglossce, 
which in Dytiscm are sol- 
dered to the sides of the 
ligula : these are very con- 
spicuous in many Coleoptera, 
and will be seen in Fig. 5 
(the labium, or lower lip, of 
Pterostichus niger, a very 
common black ground- 
beetle), in which a is the 
mentum, and l the ligulci ; c c are the paraglossae, and 
d the labial palpi. 
The next segment is the thorax, which is divided into 
three parts, the prothorax, mesothorax, and metathorax. 
The first of these, the prothorax, is considered to consist 
of two portions, — the upper side, called pronotum, and 
the under side, or prosternum. The pronotum is that 
part to which the word thorax 
is exclusively applied in de- 
scriptions, and is much de- 
veloped in the Coleoptera. In 
Fig. 6, a is the anterior, b the 
posterior, and c the lateral 
margin ; d, the medial line (of 
which the front extremity is 
called the apex, and the hinder 
the base ) ; e e are the anterior, and / / the posterior 
angles, and g the disc. 
lloth this and the following upper thoracic segment 
Fig. 0. 
Tronotum of thorax of 
D. marginalit. 
