6g8 



LIGHT FROM THE SOCIETIES. 



Cabbage-Bug— AFTER Riley. 



The Harlequin Cabbage-Bug. — No crop in the south- 

 ern states is more subject to attacks of injurious insects 

 than is the cabbage crop. Here we have all the insects 

 that attack the cabbage in the north, and many other 

 destructive species unknown in northern states. Hence 

 to bring a southern cabbage crop to maturity requires al- 

 most constant attention. Cabbages in coldframes are 

 attacked by the cabbage-plusia ( Plusia brassiccc ) and 

 aphis {Aphis brassiccc), while in the field, these species, 

 together with the 

 imported and na- 

 tive cabbage- 

 worms ( Pier is 

 rapes and prolo- 

 dice), the zebra 

 c a b b ag e-w o r m 

 (Alamestrapicta), 

 the cabbage ever- 

 gertis ( E. rimo- 

 salis), and others, 

 have full sway. If, 

 perchance, the 

 cabbages should survive the attack of these enemies, the 

 harlequin cabbage-bug (i1/«r^a?;//a histronica, Hahn), 

 finishes the work of destruction before the cabbages 

 have formed heads. This bug is a native of a southern 

 climate, probably Central America or Mexico. It was 

 first reported, within the limits of the United States, in 

 Texas in 1866. Since this date it has been gradually 

 spreading northward, and is now well distributed through- 

 out the southern states, extending as far north as south- 

 ern Illinois and Maryland. While essentially a south- 

 ern species, in a short time it will probably be common 

 in the northern states. 



Dcscriplion. — The harlequin cabbage-bug insect re- 

 ceives its common name from the reddish yellow mark- 

 ings upon its body. The mature insect measures about 

 two-fifths of an inch in length and one-third in breadth. 

 Its general color is black, but the thorax and wing-cases 

 bear yellowish red markings, while the under surface of 

 the body is white and yellow. The various stages of 

 this insect are shown in the accompanying figure, /" and 

 j-epresenting the mature forms. The pupa, shown at b, 

 differs from the mature form in being smaller, without 

 wings, and with four-jointed antennae, while in the imago 

 the antennse are five-jointed. The larva, shown at a, is 

 much smaller than the pupa and of a more yellowish 

 color. The eggs resemble miniature barrels both in 

 shape and markings. They are laid upon the under- 

 side of leaves in a double row, as shown at e. As a rule 

 there are 12 eggs in a mass, but there are sometimes as 

 many as 27, in which case they are arranged cylindri- 

 cally. The length of time required for the eggs to 

 hatch varies from less than 24 hours to 5 days. When 

 hatched, the young bugs wander about for a few hours, 

 but soon insert their beaks in the leaves. They increase 

 in size rapidly, reaching maturity, as a rule, in about 

 three weeks, the length of time required for growth de- 

 pending somewhat upon the food-plant and meteorologi- 

 cal conditions. 



The number of broods hatched during a season de- 

 pends upon the abundance of a suitable food-plant, and 

 varies greatly. If cabbages were grown throughout the 

 summer in the southern states, there would doubtless be 

 six or even seven broods during a season, but as a rule 

 there are not more than four broods a season in the 

 southern states, and probably only two in the more 

 northern states, where this insect abounds. The fourth 

 brood is produced upon fall cabbages, during September 

 and October. If a plant is attacked by large numbers of 

 these insects, it soon begins to die at the top, the outer 

 leaves turn brown, then black, and finally die. 



Remedies. — As is the case with the majority of our 

 most destructive insects, many remedies have from time 

 to time been recommended for this species. The most 

 successful one has been the Irishman's remedy for mos- 

 quitoes — to catch and kill them. Hand-picking for the 

 majority of our insects is only to be practiced as a last 

 resort. In the case of the harlequin cabbage-bug, the 

 task, even when done in the early spring, is almost an 

 endless one. Hot water has been recommended ; but, 

 while efficient, until some practical method of applying 

 the hot water in the field is found, this remedy cannot 

 be a success. Applications of lime have not given suc- 

 cess. For almost all hemipterous insects, kerosene 

 emulsion has proved to be an excellent remedy. But 

 however excellent this may be for most of the haustel- 

 late insects, it is of little practical value in the case of 

 the harlequin cabbage-bug. The exoskeleton or body- 

 wall of the insect seems to be harder, and to contain more 

 chitine than the other hemipterous insects with which 

 kerosene emulsion has proved successful. The emulsion, 

 diluted so that one part in ten is kerosene, will destroy 

 the younger larvae of the species, but upon the pupa and 

 imagoes it has no effect. Again, even though the mature 

 insects did succumb to the emulsion, great care would 

 have to be taken in applying it, because of the danger of 

 tainting the cabbages. Thus we see that a universal 

 remedy for like insects is of but little if any value in 

 this case. A simple and effective remedy for this insect 

 consists in planting a row of mustard in the center of the 

 cabbage-field at the time, or if possible, before the cab- 

 bages are set in the field. For the best results the mus- 

 tard should be in bloom in April ; it will then attract the 

 insects when they first come into the cabbage-field, and 

 they may be killed when gathered upon the mustard, 

 with strong kerosene emulsion or pure kerosene. Sweep- 

 ing with an insect-net is also good. So long as the mus- 

 tard is in bloom it will act as an efficient bait for the 

 bugs, and the cabbages will be free from them. At the 

 Mississippi Experiment Station, about an acre of cab- 

 bages were set in the field early in last February, and at 

 the same time a row of mustard-plants was set through 

 the center of the patch. In April the mustard attracted 

 large numbers of harlequin cabbage-bugs, which were 

 killed off by undiluted kerosene emulsion, This field 

 remained free from the pest throughout the entire 

 season, whereas last year the entire crop was nearly 

 ruined by it. — Hoiuard Evarts JFeed, before the 

 Society for the Promotion of Agricidtural Science. 



