after mating the females begin to insert their eggs into the tender tips
of the young shoots. The eggs hatch in a short time into larvæ which
work up the shoots until the latter are killed, when they turn and go
down the middle pith of the stems and transform in the late fall and
winter into pupæ.
There is but one brood each year.

11

b

cressoni.

a.

adult female; b, adult male; c, well developed pupa; d, very young
pupa; e and f, larvæ. (Essig, M. B. Cal. Hort Com.).

t

Distribution. The central part of the State, more particularly in the foothill regions east of the Sacramento River.

Food Plants. The native host of this insect is probably the wild rose. Raspberries suffer most from the attacks. Cultivated roses, blackberries and loganberries are also food plants.

Control.-Measures necessary to remove or destroy the eggs before the young larvæ hatch should be inaugurated. As the eggs are very tender and their locations plain, great numbers may be quickly destroyed by exerting a slight pressure over them with the fingers, which in no way injures the shoot. Cutting out infested canes is also recommended.

1

THE PEAR OR CHERRY SLUG.

Caliroa cerasi Linn. (Family Tenthredinidae).

(Eriocampoides limacina Retz.)

(Fig. 283.)

General Appearance. The adult is a glossy, black, four-winged insect about one fifth of an inch in length. The larvæ are dark olive green, slimy and from three eighths to nearly half an inch in length. Their work is very noticeable and consists in the removal of all of the upper green surface of the leaf, causing the injured areas to turn brown. Badly infested trees appear scorched as if by fire.

Life History. The eggs are oval, slightly flattened on one side and deposited under the epidermis of the leaves, usually on the under sides, by the sharp ovipositor of the female. They hatch in about. two weeks. The young larvæ cut a semi-circular hole in the upper surface of the leaf and begin to feed. They are first white and later become dark green, because of the slimy secretion. The entire green upper surface of the leaves is removed by the larvæ until only skeletons are left. The remaining under-surface turns brown. When full grown the larvæ crawl an inch or so into the ground and spin a cocoon in which to pupate and hibernate throughout the winter. The adults appear in the early spring.

Distribution. Generally distributed throughout the State.

The

FIG. 283. pear or cherry slug (Caliro a cerasi Linn.) and its work upon the leaf. (After Ewing.)

Food Plants.-Pear, cherry, plum, quince, button-bush, thorn, mountain-ash, Amelanchier canadensis.

Control. This is one of the easiest pests to control. The larvæ readily succumb to the ordinary soap or emulsion sprays and may be effectually destroyed by blowing dust upon the infested leaves.

Natural Enemies. Without doubt the reason for this pest not becoming more serious in California is due to the natural enemies which hold it in check. In this State these enemies have never been recorded but in the Middle States the egg parasites, Pentarthron minutum Riley and Closterocerus cinctipennis Ash., are quite common.

There are probably also parasites working on the larvae. This. however, has never been definitely ascertained. The predaceous bug. Podisus maculiventris Say, and the Reduviid, Sinea diadema Fab., are active enemies of the larvæ and adults. The larva of the green lacewing also devour many of the young.

THE COMMON NEMATODE OR POTATO EELWORM.

Heterodera radicicola Greef.

(Figs. 284, 285.)

Eelworms belong to a phylum of animals far below insects and are never considered in a general work on entomology, but due to the seriousness as well as the wide distribution of this worm as a pest of crops, a brief account of it is herein included.

General Appearance. The presence of this pest is told by such characteristic injuries as root knot on nursery trees, galls on tomato vines and the rough warty surface of potato tubers. The animal causing the injuries is commonly known as the nematode worm and was recently given much prominence as the potato eelworm. The males and young, the usual forms of the animal, are microscopic, transparent and shaped much like minute eels. The female is pear-shaped and pearlywhite. The eggs are oval in shape and laid in great numbers.

Life History. The young eelworms feed upon the roots of various plants causing galls or knots which may greatly impair growth. The female develops within the affected areas and begins egg-laying, the young hatching in a very short time afterwards. The winter is passed in the original host if it remains growing in the soil, such as nursery stock, but if the host is removed they feed upon various plants left in the fields. The young have the ability to encyst themselves so as to resist great extremes of weather and unfavorable conditions, so once in the soil it is very difficult to eradicate them.

Distribution. As a producer of root knot this animal is very common throughout the state, but somewhat more abundant in the central and southern parts. As a potato pest it has been discovered only in Los Angeles, Nevada, Monterey and Inyo counties.

Food Plants. According to Dr. E. A. Bessey there are four hundred and eighty species and subspecies of plants affected by root-knot. The list includes members of practically every flowering plant. Most of the garden plants are affected, as are many of the field crops and fruit trees. For definite information concerning the host plants the reader is referred to pp. 10-22, Bulletin 217, Bureau of Plant Industry, U. S. Dept. of Agriculture, by Dr. Bessey.

Control. The control of this pest is extremely difficult and eradication almost impossible. In greenhouses the soil may be sterilized with steam or formaldehyde (one part to one hundred parts of water). Rotation of crops which are not attacked by the nematode is perhaps the best control measure in the field. Summer fallow, frequently turning

FIG. 284.-The common nematode or potato eelworm (Heterodera radicicola Greef). 1, egg, magnified 200 times; 2, egg, showing developing larva within; 3, young larva, magnified 200 times; 4, same, magnified 350 times; 5, adult female and gall, magnified 70 times; 6, same, opened, showing organs of female, and eggs and young larvæ as they are found in the gall; 7, head of female, greatly enlarged; 8, part of egg tube, showing forming eggs; 9, another part of tube, with a fully formed egg in it. a, alimentary canal; e, egg tubes; h, head; o, œsophagus; s, spear. (Drawing by Newcomer.)

up the soil and allowing it to dry out, will help to reduce the numbers. Irrigated districts are more liable to become infested and are very faverable to spread and difficult of control.