76 SECOND REPORT OF THE STATE ENTOMOLOGIST. 



as represented in Fig. 10.* The eggs of butterflies having still thinner 

 shells than the above, have been exposed for hours to freezing mixtures 

 of — 22° Fahr., without injury to them. It is probable that the eggs of 

 most of our insects are in reality not frozen under the greatest cold to 

 which they would be subjected under natural exposures. Some eggs 

 of 0. leucostigma which I had taken separately from their covering 

 and left exposed during a portion of the winter, were examined by 

 me under a temperature of — 18*^ Fahr., and were found to be in their 

 natural fluid condition. 



Food-Plants. 



An important inquiry, whenever a noxious insect presents itself 

 for investigation, is its range of food, to serve as a guide to the probable 

 extent of its depredations, and the possible means of checking its 

 spread. In the year 1861, when the citizens of Brooklyn were greatly 

 excited over the increase of a " measuring-worm, "f which had become 

 an unendurable nuisance from the myriads that hung suspended by 

 their silken threads from the branches of the shade-trees of the princi- 

 pal streets, the following resolution was discussed by the common 

 council: 



" Resolved, That the owners of property having linden trees on the 

 streets are hereby ordered to remove them within ten days after the 

 passage of this ordinance, and failing to do so, shall be liable to a fine 

 of five dollars for each tree left upon the streets, after that date. The 

 street commissioner is hereby ordered to remove all trees of that species 

 that may be left on the streets after that date." 



The resolution having been referred to a committee, failed to be re- 

 ported favorably and to become a law, for the reason that upon scien- 

 tific examination it was found, that while the caterpillar was more 

 abundant upon linden trees, it also occurred and fed upon the elm, 

 weeping-willow, silver-leaved poplar, balm-of-Gilead, maple, horse- 

 chestnut, some of the fruit-trees, shrubs and herbage. 



Occasionally an insect seems to be so extremely particular in its food 

 as to confine itself to a single species, but more commonly it is found 

 feeding upon the several species of the same genus. Others extend their 

 range to the several genera of the same family, while others still, known 

 to us as polyphagous species, attack plants of very dissimilar characters, 

 comprised under several orders. In illustration of the last, we may cite 

 the habits of two species of well-known BombycidcB, viz.: Samia 



* Twenty -ihird Report on the N. Y. State Cabinet of Natural History, 1872, pp. 137- 

 141 ; Entomolog. Contrih. [No. /], 1872, pp. 5-9. 



+The larva of the snow-white linden-moth, Ennomos suhsignaria Hilbn. 



