MEMOIltS OF THE NATIONAL ACADEMY OF RCIEXCES. 13 



KoluJiv. — Of the ?> British species, 2 feeil on the oak and 1 on the hawthorn and sloe. 



Liparidw. — Of the 12 species, all feed on trees and slirnbs, except Lcvlia ca-nosa. which lives on 

 reeds and other water i)lants. It is tufted. 



Xotodontida'. — Of 24 species, 1 ( DUohn cwrulcdcephalu, which is smootli, with no i)r((tuberances) 

 feeds on the hawthorn and other plants. 



Phiti/iitc')icida\ — Of thi^ (! species, o feed on trees and 1 on a shriih. 



Endrnmidw. — The single sptcies is arboreal. 



Psi/chidn: — The 2 species, whose larval habits were known, feed on trees a)id shrnbs. 



Cochliopodida'. — The 2 species feed on trees. 



Saturuiidfv. — The single Itritish si)ecies feeds on the heather, a shrubby plant. 



Lasiocampida: — Of 11 species, 5 feed on trees, the others on slirnbs and herbs. 



Noctuo-homhyces. — All the British species are reported as "living on trees and shrubs (piite 

 exposed."' 



Bomhycoidw. — All the species of Acronycta live on trees and shrubs. 



Influence of n chaiiye from loir t > high feidinij plants, i. e., from JiriiKj on an herbaceous to an 

 nrhoreaJ station. — It appears, then, that tiie more typical Bonibyces, such as the Ceratocainpida', 

 Ueniileucida', Attaci, Xotodontians, Cochliopodidic, and Liparid;e, arc arboreal in their station, 

 "their bodies being variously protected by spines, spinnlated tubercles, hairs, or tufts. The group is 

 indeed particularly distinguished for the manifold modifications undergone by what are morpho- 

 logically seta^, and it is an interesting inquiry whether tlie great development of these spines and 

 hairs may not have originally resulted from some change in environment, such as that from 

 low feeding to high-feeding or arboreal habits. 



It uuiy be objected that the seta- and spines were originally due to the stimulus arising from 

 the attacks of parasitic insects, such as ichneumons and Tachina', or that, as hairy caterpillars 

 are not usually devoured by birds, these hairs and spines have originated through natural selec- 

 tion, and are danger signals, indicating to birds that the wearers of such hirsute and bristling 

 aimature are inedible. But while the final purpose ov ultimate use of such an armature may serve 

 the useful purpose of protection, and while natural selection may have been the leading secondary- 

 factor in the preservation of varietal and specific forms of hairy and spiny caterpillars, this docs 

 not satisfactorily account for the initial causes of the growth of tubercles, spines, etc. 



If spines and hairs form hedge-like guards against the attacks of i)arasitic insects, why are 

 they not developed as well in the great multitude of low feeders as in the less numerous high 

 feeders? It may be said, however, that Enprepia caja is movG subject to the attacks of ichneumons 

 than almost any other larv;e. (A. G. Butler in Ann. and Mag. Xat. Hist., 1S91.) I'^veryone knows 

 how efficacious any hairs or bristles are in deterring ichneumons and Tachinse from oviiiositing on 

 caterpillars, and it is well known that naked or slightly piliferous larva' are more subject to their 

 attacks than those which are densely hairy or spiuose. 



The eruciform type of larvw. — In endeavoring to account for the origin of the tubercles and 

 spines, as well as the hairs of caterpillars, let us glance at the probable causes of the origin of the 

 cateri)illar form, and of the more primary colors and markings of the skin. 



It was Fritz Miiller who, in his Fiir Darwin (18G4), niaintained that '-the so-called complete 

 metamorphosis of insects, in which these animals quit the eggs as grubs or caterpillars, and 

 afterwards become quiescent pupa^, incapable of feeding, was not inherited from the primitive 

 ancestor of all insects, but acquired at a later period." ' 



In 1869 Dr. F. Brauer- divided the larvie of insects into two groups, the campodea form aiul 

 raupen form, and in 1871^-1873 we adopted these suggestive views, giving the name of eruciform 

 to the larv;e of weevils ami other coleopterous larvte of cylindrical form, as well as to the larv;B of 

 Diptera, Lepidoptera, and Ilymenoptera, all of which are the result of adaptation, being derivatives 

 of the primary campodea type of larva. Brauer's views on these two types of larviie were also 

 adopted by Sir John Lubbock iu his Origin and Metamorphoses of Insects, 1873. 



' Facts aud Arguments for Dai'win. with additions by tlie author. Translated from tlie German liy W. S. Dallas, 

 F. L. S , Loudon, 18G'J. 



■^I3fetrachtim;5eu iiber die Verwaudlun;4 diT Insekteu im Sinne der Descendeuztheorie. Verh. K. K. Zool. hot. 

 •Ges. Wien, 1869. 



^Embryology of Chrysopa. American Naturalist, .Sei>t., 1871. 



