510 EXTERNAL ANATOMY OF INSECTS. 
nida, &e., as has been more than once observed?, the 
mandibula have been thought to represent, not indeed 
the antennze of insects, but the znner pair of those of the 
Crustacea. 
In considering the zzsertion of antennge, by which I 
mean their articulation with the head, we must advert 
first to the orifice (Zorulus) that receives them”. . This 
is a perforation of the crust of the head; commonly, 
though not invariably, circular : in Coleopterous insects 
often with concave lubricous sides, forming an acetabu- 
lum, with processes usual in ginglymous articulations, 
larger than the bulb or root of the antennze ; and which 
is commonly covered, except the central space occupied 
by the bulb, with a tense membrane. Though not in 
general remarkable, in some cases it merits attention. 
In the genus Fhipicera, the elegant antennz of whose 
males I have described in a former letter®, particularly 
the Brazilian species, it is a long process on each side of 
the nose, and might be mistaken for the first joint: in 
another Coleopterous genus, Priocera4, it has some- 
what of the shape of a trumpet: in Cupes a tubercle rises 
just above the base of the antenna: a circular process 
forms the torulus in //gora and others. It is also often 
placed in a cavity of the front, as in several wild-bees, 
Andrena, &c., and in Locusta on the sides of an elevation 
of that part®. In a large majority of insects the bulb 
(Bulbus) or ball which is received by the bed, wears the 
appearance, especially in the Hymenoptera, of a distinct 
joint; but if you carefully examine it, you will clearly 
® See above, p. 18, &c. > Prate VI. Fre. 1, 4. 7’. 
° See above, p. 319. Linn. Trans. xii. t. xxi. f. 3. 
a Tpids Jen - *Pravre VI. Fie. 4: e..¥. 
