82 



THE REPORT OF THE 



[19 



NATURE-STUDY LESSONS ON THE CABBAGE BUTTERFLY. 



(Pieris rapae.) 



By Prof. W. Lochhead, Ontario Agricultural College, Guelph. 



Introductory Note. The purpose of the following Nature-study Lessons on the 

 Cabbage Butterfly is to furnish information and question hints, regarding the structure 

 and life history of one of the most common insects of our Province, to those teachers who 

 would like to introduce Nature Study into their schools, but are prevented from doing so 

 by a lack of knowledge of insect structure and habits. 



Nearly all insects begin with the egg stage. From the egg emerges the larva, 

 (called maggot in the case of flies, caterpillar in the case of moths and butterflies, grubs 

 in the case of many beetles, and nymph in the case of grasshoppers, plant lice and half- 

 winged insects.) The larva moults, or changes its skin, as it grows, the number of moults 

 varying with the individual insect. The larva of the moths, butterflies, beetles, flies and 

 waspe, on reaching its fall growth transforms into a passive creature and sometimes spins 

 a cocoon about itself, as in the moths ; or becomes a chrysalis, as in the butterflies ; cr 

 makes a case within which it may rest quietly as a pupa, as in the flies and wasps. The 

 nymphs of the grasshoppers do not transform, but with each successive moult become more 

 like the adult insects. The adult form is usually winged, and is known as the imago, in 

 the case of the butterflies and moths. 



Nature-study lessons must be very informal in their nature. Their object is to make 

 children observe, and to draw proper conclusions from the observations ; to make them 

 see what they are looking at, and to arouse an interest in the world of nature about 

 them. 



True teachers will find that the best objects for Nature-study are the most common 

 objects about them. For this reason the Cabbage Butterfly has been taken in this case, 

 and it is the sincere hope of the writer of these lessons that many teachers will make at 

 least a beginning of this work, and give these most informal studies a fair chance among 

 the other studies of the school. 



Reference is here made to an article by the writer, entitled " Entomology in Schools," 

 published in the last annual report of the Ontario Entomological Society, 1898, in which 

 the names of the most important works on insects are given. 



Every child knows the pretty white butterflies, 

 which are so common in September in gardens and 

 along roadsides. These flit about from flower to 

 flower, evidently not caring much what kind they 

 visit. The despised dandelion, the execrable blue- 

 weed, the ubiquitous yarrow, the notorious thistle are 

 each in turn visited for the sake of the nectar or 

 honey they contain. But September is not the only 

 month when these white butterflies (Figs. 32 and 33) 

 are abroad. As soon as the snow has melted in March, 

 many of them may be seen flying about, lured by the 



bright sunshine into leaving their comfortable winter 



quarters for the deceptive breezes of early spring. 



With a relapse to cold weather many a poor butterfly* 



is frozen to death. Those that have been rendered 



only torpid the returning hot sun's rays bring back to 



life again. 



From their appearance in spring till autumn 



there is not a month when they are entirely absent, 



for there are three broods during the summer, and 



many of the late ones of one brood will be found fly- 

 ing with the early ones of the succeeding brood. 



Fig 33— The Female Cabbage Butterfly. 



The Male Butterfly. 



