506 MODERN CLASSIFICATION OF INSECTS. 
minated by a seta; proboscis generally withdrawn into the oral cavity, with 
two setz (four in the Syrphide ; mouth obsolete in the Cistride); pupa co- 
arctate, the skin of the larva forming an oval case ( Fam. Syrphide, Conopide, 
Muscide, and Wstride). 
Section 2. (Stirps 5.) Purreara Latr. (Order Homaloptera Leach). Head im- 
mersed in the thorax; claws denticulated; larva nourished in the abdomen of 
the mother, and not deposited until after it has passed to the pupa state (Fam. 
Hippoboscide and Nycteribiide). 

The four stirpes composing the first great section of the Diptera 
are distinguished by having the head more or less detached from the 
thorax, the antenne not concealed in lateral excavations of the 
head, the sete of the mouth enclosed in a fleshy canal bilobed at its 
extremity, and the claws of the tarsi not denticulated; these insects 
are oviparous, with the exception of a few Muscidz, which do not 
exclude their young until they have assumed the larva state. 
The first division comprises such species as have the antenne 
divided into a considerable number of distinct and nearly equal-sized 
joints. This division comprises the single stirps Nemocera Latr. 
In the second division (comprising the Notacantha, Tanystoma, and 
Athericera), the antennz have the terminal joints either indistinctly 
articulated or completely soldered together. 
The first stirps, Nemocera, corresponds with the genera Culex and 
Tipula of Linnzus, the antenne of which are, for the most part, com- 
posed of from 14 to 16, or from 6 to 9 joints: they are filiform or seta- 
ceous, much longer than the head, and often ornamented with whorls 
of hair, especially in the males ; the body is long, with the head small 
and rounded, the eyes large, the rostrum not concealed, with two 
external palpi composed of 4 or 5 joints, the thorax very elevated, 
the halteres long, the alule scarcely perceivable, and the legs very long 
and slender. 
Many species of the smaller size assemble in myriads in the air, 
where they perform their dance-like flights.* These assemblies (which 
consist almost entirely of males) may be observed almost throughout 
the year, and it is here where the intercourse of the sexes takes place, 
after which the females deposit their eggs, either in neighbouring 
water or upon plants. The larve are always long and vermiform, 
with a scaly head of a constant form, and a mouth presenting organs 
representing the lips and maxilla. They shed their skin previous to 
* T have observed that in these dances the insects always fly with their heads 
towards the quarter from which the wind blows. 
