SECRETARY'S PORTFOLIO. 373 



the time of strawberries until the last grapes are gathered ; not content to eat 

 entirely the fruit he attacks, but biting a piece out here and there from the 

 finest specimens, and thus destroying a far greater quantity than would suffice 

 to fill him to his utmost capacity. At the time of writing, flocks of the most 

 pertinacious specimens are destroying the best of my grapes, while alongside is 

 a patch of cabbages almost eaten up with the larvse of the cabbage butterfly — 

 nice, fat, smooth grubs, easily swallowed — but no such thing will Mr. Robin 

 look at as long as good fruit can be had. His tastes are so expensive that to 

 gratify them is to deprive the fruit grower of a large portion of his profits, 

 hence the sooner the robin ceases to be protected by legislation the better it will 

 be for all lovers of fruit. 



The insect world is composed of myriads of specimens which from their 

 varied structure and habits admit of being classified into families, each distinct 

 and usually easily recognizable to the practiced eye of the entomologist. A 

 large portion of this innumerable host is appointed to prey upon and devour 

 the other portions, and thus it appears to me that apart from any consideration 

 of insectivorous birds, that the insect world would and does, to a large extent, 

 take care of itself, and when an injurious species increases beyond its normal 

 limits, its natural insect enemies, having an unusual amount of material to 

 work on, soon become sufficiently numerous to reduce the number of the inju- 

 rious insect to its normal proportions again. As an illustration, take the now 

 common cabbage butterfly (Pieris 7'apce). This insect was in some way brought 

 from Europe to Quebec a few years ago. From Quebec it has since spread 

 over an immense area, extending now from Alabama to the waters of Lake 

 Superior, eastward to the Atlantic, and westward many hundreds of miles, and 

 over all this district it has done immense damage to the cabbage crop. Through- 

 out this area insectivorous birds of all sorts prevail. The butterfly is conspic- 

 uous, not very strong in flight, and during the day almost constantly on the 

 wing; the larva feeds in exposed situations, is of that smooth character which 

 birds are said to prefer, and, although similar in color to its food plant, is not 

 difficult to detect. Here, then, is an instance where a comparatively feeble 

 insect, particularly vulnerable to attack, has rapidly spread over a large portion 

 of this continent with little or no opposition from insectivorous birds. Indeed I 

 have never yet found or known to be found a single example either of the butter- 

 fly or its larva in the stomach of any bird. In its native home in Europe it is seldom 

 so very destructive as here, for the reason that a small four-winged fly (Ptero- 

 malus puparuni), an insignificant looking little creature, is a parasite on the 

 larva of this butterfly, and hunts its victim with the greatest assiduity; alight- 

 ing on their backs and thrusting its slender ovipositor through the skin of the 

 larva, it deposits a number of eggs there, which hatch into tiny grubs, and 

 these feed upon and eventually destroy the caterpillar. By the constant efforts 

 of this little parasite the cabbage butterfly is prevented in Europe from be- 

 coming a very serious pest. Fortunately this little friend has also been introduced 

 here from Europe, although in what manner is not known, and is rapidly 

 spreading, following in the wake of its prey, and where the parasite has fairly 

 established itself this butterfly, with its numerous progeny of green caterpillars, 

 soon dwindles in numbers so materially as shortly to cease to be so grievous an 

 evil. The butterfly spreads faster than its enemy and is usually several years 

 in advance of it, but we may confidently anticipate that sooner or later this 

 small fly will do for us what it has done for Europe — keep this troublesome 

 insect within due limits. Many other similar examples might be given. 



Further, the help of friendly parasitic insects is so much more efficient be- 



