506 PSYCHOLOGICAL PHYSIOLOGY. 



this moth. The caterpillars also of Gastrophaga quercifolia, of Cato- 

 cala Fraxini, O. c., very much resemble the dry twigs of trees, and the 

 moth of the first also closely resembles a dry fallen leaf, and may thus 

 easily conceal itself when it reposes motionless by day, as is the case 

 with most moths. 



As, in all the above instances, form and colour are the means of 

 defence, in others, it is provided by the external integument and 

 peculiar habits. Thus the caterpillars of most of the butterflies and 

 the larvae of the tortoise-beetles have a skin covered with simple or 

 ramose spines, which clothing gives them a formidable appearance, and 

 thereby partly, and partly by the pain which the spines give to the 

 oesophagus, disqualify them for being the food of birds. Others are 

 protected by their thick hairy clothing both against the prejudicial 

 influences of the elements as well as from the attacks of insectivorous 

 birds. The cuckoo alone, which likewise, from its other habits, is a 

 most remarkable bird, not deterred by this fur from swallowing such 

 caterpillars, and it is thence that its stomach is frequently covered 

 inside with hair, an occurrence that has occasioned much dispute, as 

 some naturalists maintain that this accidental clothing is the constant 

 structure of the stomach. Among the habits which many insects find 

 a protection from their enemies, we include that of many larvae covering 

 themselves with their own excrement, as is the case with the larva of 

 Lerma merdigera and some others. They then resemble little lumps 

 of dirt, and are certainly also regarded as such by many of the enemies 

 of insects. 



Other insects secrete peculiar fluids, in which they partly envelope 

 themselves and partly thereby secure themselves from the attacks of 

 their enemies. The Aphrophora spumaria is one of these, which 

 envelopes itself in a thick white frothy fluid, that comes out of the 

 anus. This cuckoo-spittle is found during summer upon almost all 

 shrubs, and particularly Avillows ; within it is seated the larva of that 

 Cicada, which undisturbedly sucks its nutriment from the plant, con- 

 stantly the while secreting fresh bubbles. The perfect-winged insect 

 has no longer the frothy covering. We find other coverings in the 

 Aphides and tortoise-beetles, which envelope themselves with a white 

 woolly or fibrous substance, the origin of which we are not yet 

 acquainted with, but it appears likewise to be produced by a peculiar 

 secretion of the skin. Other insects, as the Cantharidcs, burying- 



