¥ INSECTA. 309 
the head, the trunk, and the abdomen. On the head two compound 
eyes are usually seen, which are very large, especially in the ‘male ; 
in the most, simple eyes or eyespots are also present, usually three, 
Sometimes only two in number. The antenne are placed on the 
frons close to the eyes ; ordinarily they are, in comparison with 
those of other orders, short. Some sub-divisions of the genus 
Tipula L., make an exception to this, and the genera Macrocera 
Metc. and Megistocera WIEDEMANN are especially distinguished by 
their long antenne. The sucker consists of two, four, or six sharp 
threads, which in the last case represent the upper lip (labrum), 
the tongue (ligula), the two upper and the two under jaws. At 
the under jaws (mawille) or, when these are wanting, at the base 
of the sucker, two feelers are attached, which sometimes consist of 
five, sometimes only of two joints, or of a single joint. The under 
lip forms an univalve sheath excavated above, in which the sharp 
threads or stings reside by means of which these insects wound 5 
on this part there are no feelers. The first piece of the thorax is a 
small ring, forming a neck-ring, but the middle piece (mesothorax) 
is large, and forms nearly the whole of the thorax. To this division 
of the thorax the wings are attached. These are veined, usually 
transparent as glass, and colourless, occasionally spotted ; they are 
without that little horny point at the anterior or external margin 
(punctum callosum s. cubitale) which is seen on the anterior wings 
of the Hymenoptera. Behind the wings there is mostly found a 
small special appendage, a membranous scale (squama halterum), 
which may be regarded as a part of the wing. To the metathorax 
the poisers (halteres) are attached, which consist of a thin pedicle 
and a button. These halteres are also found in species that have 
no wings. They are to be considered as rudiments of hind-wings}. 
The abdomen is often united to the trunk by a small part alone of 
the diameter of its base, and consists of from four to nine rings. 
In the female it generally runs to a point at the posterior ex- 
tremity ; if here fewer rings are found, it is because the last of 
them form an ovipositor or case consisting of rings that can be 
pushed in and out of each other, like a pocket telescope. The feet 
are in most long and slender, and terminate always with tarsi 
1 See above, p. 252; comp. also Wrestwoon, Jntrod. to modern Classifie. 11. p. 500. 
LaTREILLE regarded these parts not as rudimentary hind-wings, for he thought they 
were attached to the abdomen. 
