1. _Papilionidae._--Containing only one British species--the beautiful Swallow-tail (Plate I, fig. 1). 2. _Pieridae._--Containing ten species. These are often known collectively as the 'Whites,' but include four butterflies that are distinguished by beautiful shades of yellow and orange. 3. _Nymphalidae._--This family contains seventeen insects, among them being several splendid species. It includes the Fritillaries and Vanessas. 4. _Apaturidae._--Of this we have only one representative--the Purple Emperor (Plate V, fig. 1). 5. _Satyridae._--Including the 'Browns' and 'Heaths,' and numbering eleven species. 6. _Lycaenidae._--Including the Hairstreaks, 'Coppers,' and 'Blues,' in all seventeen species. 7. _Erycinidae._--Containing only the 'Duke of Burgundy.' 8. _Hesperiidae._--This family contains seven British butterflies commonly known as the 'Skippers.' Although all the members of the same family resemble each other in certain points of structure, or in their habits, yet we can often find among them a smaller group differing from all the others in one or two minor particulars. Such smaller groups are called _Genera_. To make this all quite clear we will take an example. The Brimstone Butterfly (Plate II, fig. 4) belongs to the second family--_Pieridae_, _all_ the members of which are distinguished from those of the other families by the characteristics mentioned on page 141. But our Brimstone Butterfly possesses another very prominent feature in which it differs from all the other British _Pieridae_, and that is the conspicuous projecting angles of both fore and hind wings. Among the foreign species of the family we are considering there are several that possess these angles; but as there are no others among our own members, the 'Brimstone' is placed by itself in the list of British _Lepidoptera_ as the only member of the genus _Gonopteryx_ or 'angle-winged' butterflies. Thus the full relationship of this butterfly to other insects may be shown in the following manner: _The Brimstone Butterfly._ =ORDER.=--_Lepidoptera_ =Section.=--_Rhopalocera_ FAMILY.--_Pieridae_ _Genus._--_Gonopteryx_ Species.--_Rhamni_ Now, every butterfly has a Latin or Greek name in addition to that by which it is popularly known. I should have said _two_ Latin or Greek names. The first of these is always the _generic_ name, and the second is the one by which we denote the particular member or _species_ of that genus. Thus, the scientific name of the Brimstone Butterfly is _Gonopteryx Rhamni_. 'But,' the reader may be inclined to ask, 'why should we not be satisfied with the one popular name only?' And, 'If we _must_ have a separate scientific name, could we not find suitable terms among our English words to build up such a name--one that might express the principal characteristics of the insect, and also serve all the purposes of classification?'