XXvi THE HABITS AND STRUCTURE OF MOTHS. 
stigma. When we speak of the two stigmata, the orbicular 
and reniform are implied. A dark indistinct stripe, which 
frequently runs from the costa to the inner margin, between 
them, is called the central shade. Lastly, some species have 
a dark quadrangular spot in the discoidal cell between the 
two stigmata, which is often prolonged past the orbicular 
stigma, towards the base, so that the two stigmata lie in a 
dark pyramidal spot, the basal streak or band. The posterior 
transverse line is usually the only one continued on the hind 
wings, and is here, as well as on the under side, called the 
curved line. The reniform stigma appears on the under 
side as a central lunule. 
Lepidoptera owe their colours and markings to the scales 
which cover the body and wings. These are flattened and 
modified hairs. They are arranged thickly, and are attached 
by a constricted portion in more or less regular lines, in a 
way somewhat similar to the tiles on a roof. The shape of 
the scales differs very much, not only in different species, 
but in different parts of the wings of the same species. 
The larvae of most moths feed upon vegetable food; not 
only on the leaves, but frequently on flowers, fruits, or the 
wood of trees, whilst many Tineae feed upon cloth, wool, 
hair, corn, and other dried animal or vegetable substances. 
A few caterpillars, notably those of the Galeriidae, feed on 
wax in the hives of bees. 
Many moths, in common with other insects, have the 
power of producing sounds, or stridulating. The most re¬ 
markable instance of this is to be found in the great Death’s 
Head Hawk-Moth (Acherontia atropos), the largest of our 
British moths, which, in all three stages of caterpillar, 
chrysalis, and imago, is able to produce a sound. When 
disturbed or touched, the moth will emit a shrill squeak, 
not unlike that of a mouse. Various theories have, from 
time to time, been brought forward to explain the produc¬ 
tion of the sound, amongst which may be mentioned that 
of Reaumur, that it is caused by rubbing the rough ends of 
the palpi against the proboscis; and that of Wagner, who 
believes that air is forced from the air-sacs along the diges¬ 
tive canal to the proboscis, from which it issues by a number 
of small perforations producing the sound in the same way 
as in a flute. The noise made by the chrysalis somewhat 
resembles that made by the moth. The caterpillar, when 
disturbed, will draw back its head and produce a loud scrap¬ 
ing sound, probably by snapping its jaws together. Several 
other British moths stridulate, among which is the Common 
Green Silver-Lines (.Ealias prasinana), of which the Rev. F. 
