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APPLIED ENTOMOLOGY 



The Striped Cucumber Beetle {Diabrotica vittata Fab.). — The com- 

 mon Cucumber beetle is found everywhere in this country (of which it is a 

 native) east of the Rocky Mountains. It is a small beetle about a fifth of 

 an inch long, with a black head, yellow pronotum and three black stripes 

 along its yellow elytra (Fig. 107). The insect passes the winter as the 

 adult beetle in protected places, probably among dense weed growth. 

 It leaves its winter quarters early in the spring, before any of its culti- 

 vated food plants are available, and feeds on blossoms of various kinds 

 until cucumbers, squashes and the other cucurbits which are its favorite 

 food plants are available. It then attacks these and may also seriously 

 injure peas, beans, apples, and later in the season, corn. It lays its 

 eggs either singly or in clusters, in the ground 

 near the stems and roots of the cucurbits, often 

 in crevices of the soil, the total number of eggs 

 per beetle varying from a few hundred to over a 

 thousand. The eggs hatch in a week or two, ac- 

 cording to the temperature at that time, and the 

 grubs feed on the stems and roots. They are tiny, 

 white, slender, and resemble maggots more than 

 the usual forms of beetle larvae, and when full 

 grown, after 2 to 5 or more weeks, according to the 

 temperature, are only about three-tenths of an 

 inch long. They then soon change to pupae, still 

 in the ground, in which stage they remain for 

 about a week before the beetles emerge. The life 

 cycle therefore varies in length according to the 

 temperature, it being perhaps not over 4 weeks in 

 the South and 8 in the more northern States. This gives time for 

 several generations each season, and though in the North there is 

 apparently but one, this number increases farther south until in Texas 

 there may be four. 



The destruction caused by these insects when they are abundant is 

 often very great. Their first attacks come just when the young plants 

 are struggling to establish themselves and the feeding of the adult 

 beetles is often sufficient to kill them. Later in the season the beetles 

 continue feeding on the leaves and stems, reducing the vigor of the plant 

 and its productiveness, and they may also feed on the outer surface of 

 the fruit, making it more or less unsalable. They also frequently enter 

 greenhouses and attack cucurbits there. The larvae affect the vitality 

 of the plant by attacking the underground stems and roots but are less 

 injurious than the adults. 



The beetles are also injurious by carrying the "bacterial wilt" 

 disease and "cucurbit mosaic" disease, not only from plant to plant, 

 but also from one season to the next. As these diseases are serious ones, 



Fig. 10 7. — Adult 

 Striped Cucumber Beetle 

 (Diabrotica vittata Fab.) 

 enlarged about six times 

 (see hair line for true 

 length). (From U. S. 

 D. A. Farm. Bull. 1038.) 



