_Family 6, Ledridæ._--Many of the insects belonging to this family resemble beetles somewhat in appearance. _Ledra aurita_, which may be considered the type of the family, is a greenish insect, about three-quarters of an inch in length, and found on oak trees. _Family 7, Jassidæ._--This family contains a considerable number of small insects, some of them of great beauty and elegant in appearance. The typical genus is _Jassus_. _Family 8, Psyllidæ._--This is the first family of the so-called "Plant Lice" or "Blight." They resemble the "Froghoppers" in their habits of jumping. Most of them are small insects, and they subsist on the sap of plants, to which they are sometimes injurious. A few species produce galls. _Livia pyri_ is a reddish insect, abundant on pear trees. Other common species are found on the alder, ash, oak, and nettle. [Illustration: Fig. 111.--Bythoscopus Venosus (Mag.)] [Illustration: Fig. 112.--Livia Juncorum (Mag.)] _Family 9, Aphidæ._--The _Aphidæ_, or "Plant Lice," "Blight," and "Green Fly," as they are variously called, are amongst the most destructive of insects. They are small and feeble creatures, but make up for their individual insignificance by their immense numbers. They sometimes exist in countless millions, completely smothering the plants upon which they feed. Migratory habits seem to be strongly developed among the _Aphidæ_, hence it is we are so suddenly visited by such enormous quantities of the insects during hot weather in the summer time. In colour the _Aphides_ are generally green, brown, and black, according to the species. Different kinds live on different plants and trees. [Illustration: Fig. 113.--Darnis Limacodes (Mag.)] The Hop Aphis (_Aphis humuli_) lives upon the hop, and its abundance or scarcity is a most important matter to the hop-growers in this country. [Illustration: Fig. 114.--Tricophora Sanguinolenta (Mag.)] [Illustration: Fig. 115.--Aphis Tiliæ (Mag.)] One of the most destructive insects of the whole family is the Vine Aphis (_Phylloxera vastatrix_), which has committed terrible ravages at various times in most of the vine-growing districts on the Continent. The Aphides have the habit of discharging a sweet sticky substance called honeydew, of which ants are very fond. [Illustration: Fig. 116.--Lachnus Quescus (Mag.)] The reproduction of the _Aphidæ_ constitutes one of the most interesting chapters in the history of the animal kingdom. [Illustration: Fig. 117.--Aleyrodes Proletella (Mag.)] _Family 10, Aleyrodidæ._--Many of the insects of this family resemble moths in appearance. Indeed, the typical species, _Aleyrodes proletella_, a very small reddish insect, was formerly considered to be a moth by the older writers on entomology. _Family 11, Coccidæ._--This family contains the Cochineal Insects, the Scale Insects, and their allies.