308 
HALF HOURS WITH INSECTS. [Packard. 
prey. The construction of their nests does not require so 
much intelligence as is shown by the ant lion. The larva 
is a hideous being, with a large horn on its back, by which 
it is enabled to prop itself up in its hole. 
None of the flies are architects. Some involuntarily form 
galls of various shapes, in which the maggots are domiciled. 
For example, the gall-fly of the willow forms the familiar 
pine-cone-like swelling (Fig. 239) found on willow twigs, 
while another kind forms a mass of willow leaves like the 
sprouts on a cabbage (Fig. 240). The many-chambered gall 
of the gall-gnat of the grape vine is represented by figure 
241 (this and the two preceding figures from Riley), and 
Mr. Riley has delineated the filbert gall which grows in large 
masses on the grape vine (Fig. 242, representing, a mass of 
them of the natural size). 
Among the caterpillars of the moths are many of the 
smaller kinds which mine the leaves of plants, or tunnel the 
stems; others, more skilful, cut out portions of leaves and 
20 
