is distinctly a native pest. As early as 1843 it was reported as an injurious insect, and in 1864 Dr. Fitch* published an article on the beetle in which he states that for more than twenty years he has had to protect his cucumber vines against the attack of these beetles.

In 1781 this beetle was described by Fabricius, in his Species of Insects, Vol. I, p. 148, under the name Cistela melanocephala, or the "Black-headed Cistela." A few years afterwards it was placed by him in the genus Crioceris, but as there was already another species having the same name he renamed it vittata, or "Striped Crioceris." Inasmuch as this beetle was not known at this time to be a pest outside of America, Gmelin gave it the name Cryptocephalus americanus, which was quite appropriate. Shortly after, Olivier determined the place of this insect to be in the genus Galeruca. Chevrolat, however, proposed a division of this genus, giving it the name Diabrotica, in which it has since remained.

FOOD PLANTS.

It is well known that this beetle feeds not only on the cucumber, squash and melon, but on all related Cucurbitaceae. It is frequently found feeding on the foliage of other vegetables, and the past season attacked the leaves of young peas and beans at the Station farm. Sirrine of New York, in 1899, reported that it feeds on the flowers of the apple, cherry, choke cherry and wild balsam apple. In 1916 a row of peanuts, Arachis hypogoea Linn., adjoining this field were found infested with these beetles. They are quite frequently found feeding on' goldenrod and sunflower

blossoms.

INJURY.

These beetles feed during the whole season from late in the spring until October or later in the fall on cultivated or wild plants. The greatest amount of damage is caused by the adults just as the plants start out of the ground. The beetles attack the cotyledonous leaves, and in 1916 they had destroyed the entire crop before the majority of these leaves had appeared above ground. Although the greatest loss is caused at this time,

* 10th Report, Fitch's Noxious Insects of New York.

later in the season they feed on the stems of the vines and also on the flowers. This causes a weakening of the vines and to some extent prevents the setting of the fruit. The larvae feed on and tunnel in the main stems; (see Plate V); however, the damage caused by the larvae is not to be compared with that of the adult because after the stalks start to shoot out running vines they are generally vigorous enough to stand the attack from these insects. They prefer only the young and most tender parts of the plant and when the plants become woody the beetles cause no more damage except to the leaves and blossoms. It is, therefore, evident that the most damage is done when the plants are small, and the wilting of the vines, due to the work of the larvae, is not very great. The mining of the stems by the larvae has not very much immediate effect on the plants but this season there was an increased tendency of both cucumber and squash vines to develop certain forms of fungous diseases.

The loss incurred by disease due to the feeding of the larvae has been estimated at from ten per cent. to forty per cent. of the crop. Several cucumber vines this year, when from two to three feet long, became infested with a wilt, determined by the botanist of the Station to be the Fusarium wilt. Some of the more common diseases of cucumbers occurring in Connecticut are the downy mildew, Pernoplasmopara cubensis (B. & C.), Clint., and anthracnose, Colletotrichum lagenarium. This season there was comparatively little damage done to the fruit; nevertheless, the larvae work in the rinds of the fruit, causing a warty appearThe feeding of the larvae also provides for the growth of rots and bacterial diseases. These beetles, besides being destructive to cucumbers, cause considerable damage to melon and squash, especially in market garden sections. They cause the most loss in sections where there is a scarcity of wild flowers. These beetles originally fed on the blossoms of such flowers as the goldenrod and wild species of the gourd. Although at the present time they do feed on some wild flower blossoms, they prefer to remain in vegetable gardens until the cold weather drives them to their hibernating quarters.

ance.

LIFE HISTORY.

ADULT. The beetles emerge from their hibernating quarters in May and June, although a few beetles may be found during

warm sunny days in April. The beetles appearing early are undoubtedly the ones that do not go into the ground to hibernate but find suitable quarters in farm buildings. The ones appearing early feed on a large variety of food plants until the squash and cucumber plants break through the ground. At this time they are ravenous feeders and usually feed a week or ten days before mating. The adults have a habit of hiding in cracks in the ground and cause considerable damage before one realizes that they are present in any great numbers. Some days, especially when it is cloudy, scarcely any beetles can be found in sight, but if the earth is disturbed a great many of them will fly about. They not only hide in the loose soil but also on the under side of the leaves. They soon begin to mate and the females shortly after begin to lay eggs. The tendency to pair is very strong and this often continues long after the egg-laying period.

EGG. The eggs are laid promiscuously (see plate IV, a), the female dropping them in crevices of the soil near the stems of the plants. They are also commonly found underneath the leaves; in fact, it appears that the female drops eggs anywhere she happens to be feeding or hiding. In the field the eggs are deposited singly. Sirrine reports that in all his field observations he had never found eggs deposited in clusters although females in confinement deposited a great many eggs in a few hours, a large proportion of these being laid in clusters. The number of eggs deposited varies from about thirty up to one hundred. The largest number ever observed deposited by a single female is one hundred and seventeen. From recent observations the female deposits all of her eggs in a single season. Some female beetles which have been kept in captivity have been known to lay eggs a second season. This was the case of a female of Calosoma frigidum Kirby, according to Mr. Burgess. The hatching period of the striped beetle eggs varies according to the temperature. Experiments have proved that in an average temperature of 74°F. the eggs hatch in eight or nine days.

LARVA. The larval stage is passed in the soil and may be found in the stems or on the fruit where it touches the earth. The larvae, however, can only mature in moist earth. When the larvae first hatch, unless they have moisture they will live but a short time. It requires about a month from the time the egg hatches until the larva becomes full grown. It then leaves the

plant and makes an oval, earthen cell in moist earth in which it pupates.

PUPA. The pupal stage is passed in from six days in warm weather to two weeks in colder weather. In this locality there is but one generation annually, although in Washington there are at least two, and possibly three generations in a single season.

DESCRIPTION.

ADULT. The general appearance of the striped beetle is shown on plate IV, b; it is a glossy, bright lemon-yellow, rather small beetle with a black head. The antennae are also black with the exception of the first three joints, which are a yellowish color. They are about two-thirds the length of the body. The thorax is not quite as broad as the wing covers. There are two indentations on the upper side of the thorax a little more than half way from its center. The wing covers are oval in outline and slightly convex. Each wing cover has nine furrows running lengthwise; in each of these furrows there is a row of small punctures. There are three black stripes on the wing covers, the middle one being on the suture. The wings are of a gray-brown color. The beetle measures about two-fifths of an inch in length (see plate IV, b), and is nearly half as wide as long..

EGG. The egg is of a light yellow or lemon-yellow color and is shown on plate IV, a. It is somewhat smaller than some of the other species, such as Diabrotica 12-punctata, and averages 6 mm. in length and about half as wide. It has the same markings as those of Diabrotica longicornis Say, figured by Forbes in the 12th Report on Insects of Illinois, page 18.

LARVA. The larva is a small, slender, soft "grub," dullwhite, with a dark brown head and anal plate, the thoracic plate being light brown in color. It measures about one third of an inch in length, and is about one-tenth as thick. It has six thoracic legs and one anal proleg. It is covered with a few scattering hairs.

PUPA. The pupa is of a yellowish-white color. Its appearance is rather unique inasmuch as the antennae, legs, wing and wing covers are enclosed in separate sheaths, thus being free from the body.

Adult, larva and pupa are shown in figure 2.

PARASITES.

One of the most important natural enemies of the striped beetle is a tachnid fly, whose life cycle is passed within the adult beetle. This fly proves to be very destructive and undoubtedly helps. greatly to keep this pest in check. It is known as Celatoria

*

diabroticae Shimer. Some of the ground beetles and certain species of ants feed on the larvae.

Figure 2. The striped cucumber beetle: a, adult beetle: b, larva; c, pupa; d, side view of anal segment. All greatly enlarged. (After Chittenden, Circular 31, Bureau of Entomology, U. S. Department of Agriculture.)

The half acre used in this experiment was planted to twelve rows of cucumbers and fourteen rows of squashes. The treatments given were as follows:*

Rows 1, 2 and 3.

66
4 5.

7.

**

66

แ

9.

Fine coal ashes.

Chittenden, F. H. Insects injurious to Vegetables, Fig. 105, p. 157. The beetles were so abundant it was useless to leave any check rows. Consequently it was thought best to use the ground to the best advantage and try to protect all the rows without leaving any for check rows.