74 MODERN CLASSIFICATION OF INSECTS. 
are generally accompanied by three minute simple ocelli, placed in 
a triangle, or curved line, upon the crown of the head. M. Dufour 
has described a species of Anoplius (Fam. Pompilidz), having only a 
single ocellus (Ann. Soc. Ent. de France, tom. ii. p. 484.) ; and in the 
apterous females of certain genera they are entirely wanting. In a 
very few species, the eyes themselves appear also to be entirely 
wanting. 
The antenne are very variable in structure in the different groups ; 
those of the males are generally much more developed than in the 
other sex, and often furnished with various appendages. The num- 
ber of the joints varies very greatly in the aberrant tribes, or those fur- 
nished with an ovipositor ; but, in the typical aculeate division, these 
organs are filiform, or setaceous and simple, and almost uniformly 
composed of thirteen joints in the males, and twelve in the females. 
The mouth is composed of a membranous or leathery labrum; a 
pair of horny mandibles, a pair of long membranous or leathery max- 
ila, each provided with an articulated palpus, varying in the number 
of its joints from one to six; and a lower lip, or tongue, having a basal 
mentum ; lateral palpi, also varying in the number of their joints from 
one to four, and occasionally with slender filaments, or paraglossee : 
this organ varies in length according to the size of the maxille, in the 
motions of which it participates. In many species the mandibles 
cannot be regarded as organs of manducation, being employed solely 
in the construction of the nest; the maxilla, also, are unfitted for 
mastication, uniting with the lower lip and its appendages, to which 
they form a kind of sheath, and forming an elongated rostrum, of very 
complex construction, by which they collect their food, which consists 
of honey, and forming a passage to the entrance of the alimentary 
canal. This latter character may, indeed, as St. Fargeau suggests 
(Hist. Nat. Ins. Hymén., tom. i. p. 80.), be regarded as the most dis- 
tinguishing trait of the order. 
The body of these insects is covered with a hard scaly integument, 
the three portions of which it is composed being ordinarily distinct 
from each other. 
The head is attached to the thorax by the narrowed part of the 
prothorax ; it is generally transverse, and narrower than the thorax. 
The thorax generally forms an oval mass ; the prothorax, to which 
the fore legs are attached, is of very small size, owing to the necessarily 
increased development of the other thoracic segments supporting 
