106 



Faidherhia beIonc(s to the Bombycid Division of the moths. It is 

 l^artial to the species of Zizyphiis, especially the Siddem (Zizyphus 

 orthacantha) ; and it is thought, that it will be exceedingly valuable, 

 when established in Algeria, as the silk, though of a bad colour, a 

 pale grey, winds off with ease, and is produced in very large 

 quantities. Whereas the mean weight of a single cocoon of the 

 common silk-worm is 290 millegi^ammes, and of an Ailantus worm 

 255, that of Faidherbia attains to no less than 633 millegrammes.'^ 



North America possesses numerous large Bombycid moths, more 

 than one of which might probably be domesticated with profit. 



The pretty pale green Tropcea luna chooses the sycamore and 

 the oak for its food plants. Callosamia promethea supports itself 

 on two species of the bay, Saurus sassafras and benzoin. Callosamia 

 cecropia occurs on the wild plum (Pruniis pennsylvanica).^ The 

 cocoon of the last-named insect is of a yellowish bro^vn and larger 

 than a pigeon's egg ; the silk has been carded and converted into 

 stockings. Another species of Callosamia, named Angulifera, ^ is 

 partial to the cherry, whilst Telea polyphemus, the larv?e of which 

 feeds on the oak and elm, may some day i)rove of economic value. 

 It has been reared on a large scale at Boston, by a Mr. Troubelet, 

 who speaks highly of the quality of the silk produced by the 

 *'Pol;y^^liemus Worm." J 



It will be observed that the foregoing moths belong without 

 exception to the same subdivision of the order Lepidoptera — that of 

 the Bomhycids ; in fact, the members of this group appear to 

 enjoy a monopoly of the art of s^Dinning a serviceable silk. 



The only moths outside this subdivision, whose threads have been 

 put under contribution — and that only on a limited scale — are the 

 Ermines, as they are named, from the fact of their snowj^ wings 

 being studded with velvety black sx)ots. They constitute the genus 

 ffyponomeuta, of the sub-order Tineids. 



Though individually small these insects are capable of producing 

 a large amount of silk, and (it may be added) of working an 

 enormous amount of mischief ; because the larv?e are gregarious in 

 their habits ; in other words, the caterpillars, on leaving the eggs, 

 instead of separating and going each its own way, all keep together, 

 and spin, in common, a large silken vv^eb, wherein they congregate, 

 when not feeding. 



In Great Britain, and in most of the temperate parts of Europe, 

 they infest orchards, and in years when they are abundant, often 

 commit sad havoc, not merely by devouring the leaves, but by 

 enveloping the branches in a silken covering, thus excluding the air 

 and spoiling the fruit. In the year 1841, they appeared in vast 

 numbers in the heart of London ; in many of the squares not a 

 hawthorn tree was to be seen, whose branches were not enve- 

 loped in a web, giving the tree the appearance of being covered 

 by a fine cloth. § A year or two j)reviously the cider makers of 

 Normandy — and this title includes nearly every family in that 

 fertile province of France — were almost driven to despair by 

 the ravages of one of these Ermine-moths, Hyponomeuta cognatella. 

 It was hopeless to attempt to destroy them, and the unfortunate 



* Comptes Eendus,4865. + Duncan. Nat. Library, xxxvii. 



J American Naturalist, 1870, § E. Lankester, Entomologist, 1841. 



