INTERRELATIONS OF INSECTS 309 
the beetles eat aphides, but also fungus spores and pollen in 
large quantities. Though Lepidoptera are pre-eminently phy- 
tophagous, the larva of Feniseca tarquinius is unique in feeding 
solely upon plant lice, particularly the woolly Schizoneura tes- 
sellata of the alder. Among Diptera, Asilide, Midaidze, 
Therevidee and Empididze are the chief predaceous families. 
Asilidze ferociously attack not only other flies, but also beetles, 
bumble bees, butterflies and dragon flies; as larve they feed 
largely upon the larve of beetles. Many of the larve of 
Syrphidz prey upon plant lice, and the larve of Volucella feed 
in Europe on the larvee of bumble bees and wasps. Of 
Hymenoptera, the ants are to a great extent predaceous, 
attacking all sorts of insects, but particularly soft-bodied 
kinds; while Vespidze feed largely upon other insects, though 
like the ants, they are fond of the nectar of flowers and the 
qmices-of fruits. 
Parasitic Insects.—Though very many insects occur as 
external parasites on the bodies of birds and mammals, very 
few occur as such on the bodies of other insects; one of the 
few is Braula ceca, a wingless dipteron found on the body 
of the honey bee. 
A vast number of insects, however, undergo their larval 
development as internal parasites of other insects, and most 
of these parasites belong to the two most specialized orders, 
Diptera and Hymenoptera. 
The larve of Bombylidz feed upon the eggs of Orthop- 
tera and upon larve of Lepidoptera and Hymenoptera. 
Tachinidze are the most important dipterous parasites of other 
insects and lay their eggs most frequently upon caterpillars ; 
the larvze bore into their victim, develop within its body, and 
at length emerge as winged insects. These parasites often 
render an important service to man in checking the increase 
of noxious Lepidoptera. 
The great majority of insect parasites—many thousand 
species—belong to the order Hymenoptera, constituting one 
of the primary divisions of the order. They are immensely 
