165 



believe they are that species. The varieties of cabbage most attacked belong to the 

 class known as Savoys, which have hard, close heads. A few other varieties, how- 

 ever, were also attacked. The eggs are apparently laid near the top of the head and 

 the young maggots work their way down between the leaves, generally following the 

 course of a mid-rib, frequently confining their operations to that alone, but also 

 sometimes boring straight into the heart of the cabbage and thus rendering it unsale- 

 able. There does not appear to be much decay of the tissues, but simply an irregular 

 channel is eaten out, which is filled with the shredded tissues of the leaf and a 

 mucilaginous exudation from the plant. 



Some of the larvse have turned to pupse inside the cabbages ; but others placed 

 in breeding jars have buried themselves in the soil. 



I have so far received no complaints of this injury from outside sources; but 

 should it become widespread, it will be a matter demanding the earnest attention of 

 entomologi^^ts, to discover a remedy as soon as possible. As many as twenty larvae 

 were taken from one head. 



In Prof. Eiley's report for 1884, mention is made of a summer attack upon the 

 mid-ribs of the leaves, as follows : " Our first acquaintance with this insect was in June, 

 186*7, when Prof A. N. Prentiss, then at the State Agricultural College, Lansing, 

 Mich., sent us specimens of the larvse, with an account of their gnawing and exco- 

 riating both the stems and roots of cabbages, and thereby doing much damage. 

 They transformed June 21-25, just below the surface of the ground, to puparia of a 

 honey-yellow colour, some lighter, some darker, and the first flies issued June 29 

 onward. We have since (in 1878) found the species not only working in the normal 

 way in the roots, but also burrowing in the stout mid-ribs of the leaves. From June 

 8-13, quite a number of the perfect flies were obtained." This summer attack I have 

 also occasionally noticed at Ottawa; but it is of far less importance than the winter 

 attack above-referred to, because when the individual leaf only is destroyed, the plant 

 soon replaces it, and when, as is usually the c:ise in this attack, the stem is also 

 injured, the plant is destroyed early enough for it to be replaced by a healthy one. 

 This summer attack also has been very rare in my expei'ience ; the winter attack, 

 however, is more serious, because the maggots work in the solid heads after they are 

 stored in the root-house. I am under the impression that in ordinary summers, here, 

 there is not sufllcient moisture in the atmosphere above the surface of the soil to allow 

 the young maggots to live long enough to penetrate the epidermis of the leaf before 

 they are dried up. In the case of the eggs of the Onion Maggot {Phorhia ceparum) out 

 of several clusters of eggs laid in the axil of the fii-st leaf, where the ground beneath 

 had been sprinkled with sand saturated with coal oil, not a single maggot efiected an 

 entrance, and in only one instance have I ever found an individual of this insect in 

 the stem of the onion above the surface of the ground. 



The Diamond-back Moth {Plutella cruciferarum, Zell.) 



Attack. — Small green, exceedingly active, caterpillars about J of an inch in 

 length, which attack the leaves of cabbages, eating numerous small holes through 

 the younger leaves and irregular blotches from the under surface of the older leaves. 

 When disturbed they run backwards, wriggling their bodies violently from side to 

 side, and fall to the ground by means of a silken thread, where they lie quite still. 



This little insect although very small is a serious pest to cabbages every year 

 in some parts of British Columbia, the North-West Territories and Manitoba, and in 

 1889 was extremely troublesome upon the Experimental Farm here. The eggs are 

 laid on the under sides of the outer leaves of cabbages and many other plants belong- 

 ing to the same botanical order. I have found the caterpillars on turnips, cabbage, 

 cauliflower, pepper-grass (Jjepidhcm), shepherd's purse, and in 1889 it was an inces- 

 sant and most troublesome pest upon garden stocks and wall-flowers from about 

 .July till the frosts set in in November. The caterpillar is pale green in colour, some- 

 times almost yellow, and bears some black dots and short bristles in regular series, 

 as shown at Fig. 5 — b-c. When full grown the larv£e spin pretty open net-work 



