VEGETABLE CROPS. 



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Insect Pests of Cabbages and Cauliflowers.* 



The Diamond-backed Cabbage Moth (Plutella maculipemtis). 



Under the name of "cabbage grub" or "cabbage worm," the caterpillar of 



this little moth, once a European turnip pest, but now world-wide in its range, 

 is well known to Australian cabbage- growers, as well as to the cabbage 

 consumer when he finds the little green worms among the leaves of his 

 purchase. 



The life-history of the Diamond-backed Cabbage Moth is so well known that 

 it need only be briefly outlined in these pages. The moth, on the wing among 

 the herbage, appears to be of a 

 uniform brown tint, and does not 

 show the distinct angular row of 

 pale markings along the upper 

 margin of the folded wings from 

 which it takes its popular name, 

 "diamond-backed," and by which 

 it can be so easily identified among 

 pinned specimens from all other 

 allied species. It measures slightly 

 over half an inch across the out- 

 spread wings. Emerging from 

 the stout chrysalid skins, which, 

 attached to bits of cabbage leaves, 

 stalks or weeds, have protected 

 them, under shelter of their 

 flimsy cocoons, through the winter 

 months, these active little moths 

 lay their eggs upon the foliage of 

 the young cabbage plants, and 

 remain in hiding among the weeds 

 and on the under side of the cab- 

 bage leaves. As soon as the fine 



weather sets in, if one walks through a cabbage patch, and sees numbers of 

 small brown moths rising up before him, he will, even if the plants have not 

 begun to show its effects, know that the cabbage moth is about. If he investi- 

 gates the plants, he will find the leaves marked with glassy spots where the 

 tiny, black-headed, pale green caterpillars have been at work. So like the 

 surface of the leaf are these caterpillars in coloration that they would be easily 

 passed over, if it were not for their gnawing off the epidermis of the leaf. 



As they increase in size, they become slender, bright green caterpillars 

 (popularly known as " cabbage worms "), and rest upon the surface of the 

 leaves, gnawing holes right through them. At first they confine their 

 attention to the larger outer leaves, but as they increase in numbers they 

 gnaw all through the plant, and if they are allowed to reach this stage the 

 cabbage or cauliflower is soon of no marketable value. The caterpillars are 

 active little creatures, and if touched they roll away or drop from the leaf to 

 the ground, often hanging suspended on a silken thread, and thus they escape 

 their many enemies. When full grown, they betake themselves to the shelter 

 of the under side of the leaf upon which they have been feeding, and spin 



* Compiled by Officers of the Entomological Branch. 



Diamond-backed Cabbage Moth, viewed 

 from above. [Enlarged.]. 



