II INTRODUCTION. By L. B. Prout. 



The larva is almost invariably specialized by the loss of the three anterior pairs of ventral claspers, only 

 those on the sixth abdominal segment and the anal pair persisting. It has been suggested that by this form 

 (which is nearly ahvaj's accompanied by a great elongation of the middle segments) the creature acquires a 

 longer reach among its foodplant, whether for obtaining more food with an econonomy of movement, or for passing 

 from twig to twig, or from branch to branch, in its arboreal habitation ; it is significant in this connection that 

 a very large percentage of the species in this family, as compared with most of the others, inhabits trees or 

 shrubs rather than low growths. It has also been suggested that the peculiar ,, looping" gait which results, and 

 which has gained for the larvae the popular EngUsh name of ,,loopers", and for the family that of Geometers 

 (ground-measurers) is favourable to rapidity of locomotion. Be this as it may, it is certain that many of the lar- 

 vae have been enabled to assume a most wonderful likeness to twigs. The food-plant is grasped firmly with the 

 prolegs, the body rigidly extended at an angle, the true legs and head closely tucked together, while there are 

 sometimes also characteristic sharp bends in the body. In addition, to enhance the resemblance, there are often 

 small humps suggesting nodules, leaf-buds or other excrescences of the twig. In such a posture the larva will 

 remain absolutely motionless for many hours, and it is often extremely difficult for even the practised eye to dis- 

 cover it. The absence of the middle legs, however, is by no means restricted to the twig-like larvae, but is vir- 

 tually, as has been indicated above, a family character. Many are leaf-green in colour, and rest along the midrib 

 of a leaf. Some (notably Eu-pithecia) are flower-feeders, and show a marvellous adjustment to the coloration 

 of the flowers which they inhabit. In the case of the polyphagous ones there is consequently a wide range of co- 

 lour variability; and it is certainly possible in some cases (I have mj'self tested it by transferring Eu-pithecia 

 absinthiata from Eupatorium to Senecio) to bring about complete colour changes within the life of a single larva. 

 Similarly with, the simply dimorphic larvae (which have a green and brown form to assimilate to different twigs) 

 PoTJLTON and others have demonstrated that a change of colour can often be brought about by a change of en- 

 vironment. Nor must mention be omitted of the fact that some larvae in the ordinary course of their life-his- 

 tory undergo a change to correspond with that in their food plant ; Hipparchus papilionaria is' a well-known 

 example. In some larvae, again (as Cleowdes licJienaria or the Australian genus Dedana), the resemblance is 

 to lichens, and some of the twig-like larvae (as Gonodontis bidentata) produce, under favourable environment, per- 

 fectly lichen-coloured aberrations. 



Very few kno^vn Geometrid larvae are protected by passing their lives in literal concealment, scarcely 

 any, apparently, hiding below ground or feeding in roots, like many Noctuids. A Californian species, Meso- 

 leuca implicaia, is said to have quite the same habit as the Palearctic Agrotis ripae, burying itself in the sand 

 beneath its food-plant, Abromia latifolia. A few Eupithecia, Perizoma, etc., live concealed in the seed-vessels 

 on which they feed, or commence life thus (or burrowing into buds) and only assume the external habit at a 

 later stage. Other Larentiids (as Hydriomena, Eulype, Operophtera) spin together leaves, residing in the do- 

 micile so formed. Certain Hemitheinae {Evchloris, Synchlora, the large genus Comihaena, etc.) clothe them- 

 selves with fragments of leaves or flowers, without, however, making actual cases as do the Psychidae and others. 



In more aggressively defensive arrangements, such as poison-glands or urticating hairs, or e^en terrifying 

 markings or attitudes, the Geometrid larvae are generally altogether deficient. Most are, hoAvever, provided 

 with a fluid secretion, usually of a dark green colour, which they discharge from the mouth when attacked 

 and which, although perfectly innocuous to man, is no doubt of some service against certain of their enemies. 

 Some species, such as the common Eurojjean Lithina petraria, when touched drop to the ground and throw 

 themselves about with the most violent contortions. 



The coloration of the moths is also as a rule closely adapted to the surroundings among which they rest 

 by day. Many sit with wings outspread on tree-trunks, fences or rocks, and are of sombre brown or grey tints 

 or coloured like the lichens. It is noticeable that those which, while frequenting such situations, are least per- 

 fectly concealed (chiefly iarejiiMwae) are extremely wary, flying off briskly on the approach of danger, and 

 these possibly owe their safety quite as largely to this cause as to the other (assuming that their enemies are 

 things that creep rather than things that fly); but there is no doubt that even in these cases a general adap- 

 tation to the environment gives them a good deal of security at rest, and saves them from the constant ne- 

 cessity of fleeing from place to place. Many examples among the Palearctic species of Larentia (sens, lat.) 

 will occur to the field-naturalist, of species wliich, although fairly consjDicuous when actually looked at upon 

 the trees, yet on account of the broken outlines created by their markings harmonize quite sufficiently well with 

 their surroundings to be really inconspicuous to the casual passer-by; such are picata, truncafa, hlomeri and 

 many others. The moths which sit among leaves are often of a beautiful green (the subfamily Hemitheinae, 

 with only a few exceptions) or of rich golden brown hues assimilating to the withered leaves ; but often the white 

 ones (such as the Deilinia group, some Acidalia, etc.) are almost as well protected in such situations on account 

 of the suggestion of bird-droppings, or occasionally of white flowers. But indeed the subject of these cryptic adjust- 

 ments is a limitless one, and almost every separate species is worthy of separate study in relation to its environment. 



Many species of Geometridae, however, are true day-fliers, and many others are so easily disturbed by 

 day as almost to give the impression that this is their natural time of flight. In the alternations of bright light 

 and shadow caused by the sunshine among trees or undergrowth, black moths like Odezia atrata or black- 



