488 
THE STUDY OF INSECTS. 
frontal suture is present. The legs are broadly separated 
by the sternum ; they are comparatively short and stout; 
the tarsal claws are strong and are often furnished with 
teeth. The winged forms vary greatly in the venation of 
the wings. The veins near the costal border are usually 
strong while the others are weak. Figure 595 represents 
the venation of Olfersia . In this genus veins III 2 -|- S and 
III 4 -f-» separate near the base of the wing. In Hippobosca 
they separate at or beyond the middle of the wing. 
Even more remarkable than the parasitic life of the adult 
flies is the mode of reproduction of these insects. The egg 
is hatched within the body of the parent, the larva is nour¬ 
ished in this position till it is full-grown, and is not born till 
it is ready to change to a pupa. This mode of reproduction 
is also characteristic of the two following families, which are 
frequently on this account classed with this one as a division 
of the Diptera, termed Pupipara (Pu-pip'a-ra). 
The most common member of the Hippoboscidse is the 
Sheeptick, Melophagus ovinus (Me-loph'a-gus o-vi'nus). This 
is a wingless species (Fig. 596), which lives upon 
sheep. Hippobosca equina (Hip-po-bos'ca e-qui'na) 
is winged and lives on the horse. Olfersia anieri - 
cana (Ol-fer'si-a a-mer-i-ca'na) is also winged and 
is common on owls and other birds. The species 
fig. 596. t j ie g enus Lip 0 ptera (Li-pop'te-ra) are winged 
at first and live on birds ; later they migrate to quadrupeds, 
