Reading course in economic entomology

UNIVERSITY OF CALIFORNIA Agricultural experiment Station

COLLEGE OF AGRICULTURE E. W. HILGARD, DIRECTOR

BERKELEY, CALIFORNIA

CIRCULAR No. 10.

(March, 1904.)

READING COURSE IN ECONOMIC ENTOMOLOGY.

By C. W. WOODWORTH.

(The work of the Experiment Station is generally quite distinct from that of the
Department of University Extension in Agriculture, but in this instance it seemed wise
to issue a joint publication. It concerns primarily the work of the latter department,
but is also intended for the training and direction of a set of reliable volunteer observers
through whom the Station may expect to secure valuable data not otherwise easily
obtainable.)

The desire has been very widely expressed for individual or class
instruction along agricultural lines by those unable to attend the
University. One of the topics upon which inquiry has been particu-
larly made is that of Economic Entomology. We have decided, there-
fore, to offer a reading course in this subject calculated to give the
student a broad general knowledge of the facts of the science, and an
acquaintance with the most recent publications of the working economic
entomologists of the country.

GENERAL DIRECTIONS.

Those desiring to enroll as readers should make application to
W. T. Clarke, Assistant Superintendent, University Extension in
Agriculture, Berkeley, California. Each reader will be furnished with
a set of bulletins which will serve as text-book. He will be expected to
make himself thoroughly familiar with their contents. A circulating
library is also provided, for collateral reading and reference. These
books should be read as carefully as possible in accordance with the direc-
tions given in this circular. After the completion of the work here
outlined, an examination will be arranged for with an instructor in the
Entomological Department.

Those who thus complete this course will be eligible to advanced
standing in Economic Entomology should they subsequently enter the
University. This course may, therefore, be considered a University
course given in absentia, and must be pursued with the same care and
thoroughness as though done in the class-rooms at Berkeley. The
names of those completing this course will be kept as a special mailing

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list, and they will receive thereafter not only the bulletins of the Experi-
ment Station, but also all circulars and notices of special publications
of the Entomological Department.

Those reading in this course by themselves will receive the books
forming the reference library, one at a time by express, and will be
required to pay the express charges both ways. There will be no fees
or other charges to be paid by the student, except for damage to books
beyond reasonable wear. The Entomological Department will attempt
to answer letters of inquiry of readers in this course, and to assist them
in any difficulties they may find in their studies.

Reading Circle. — It is strongly recommended that wherever possible
a reading circle be formed for mutual helpfulness in this study. Where
this is done, the whole reference library will be sent to the member
designated by the circle, and the distribution can be arranged to suit
the convenience of the members. We would suggest that the circle form
an organization, charging a sum for membership sufficient to raise a
fund not only to pay the express charges on the circulating library, but
also to buy a few books on the subject for the local library or as a
nucleus for a public library, if one is not already in existence in the
community. Thus the work of the circle will become more permanent.

Another advantage of the organization of a reading circle will be the
possibility of personal instruction by a visit, to the community, of a
member of the staff of the Entomological Department. Where possible
some such arrangement as the following will be made: After the com-
pletion of the course by a circle a date will be arranged for this visit.
The instructor will spend half a day with the members of the class,
visiting orchards and studying the insect pests out of doors. Another
half day will be spent with those who have followed the course, in
answering questions and discussing difficulties met with by members of
the class, and in holding the examination. The evening may be devoted
to a public lecture, where a topic of general interest will be discussed.

WHY STUDY THIS SUBJECT.

The study of Economic Entomology appeals more or less strongly to
a large number of people and is valuable for two important reasons:
its educational value and its economic value.

Educational Value. — The importance of the educational value of this
study may be overlooked at first sight by the practical grower, but he
will be none the less ready to acknowledge its claim when it is clearly
seen. What is meant by the educational value of a study is the develop-
ment of power that arises from it. If one can become more able to
observe clearly, to quickly comprehend the significance of what he sees
in the practical problem he has in hand, and learns how to direct his

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observations so that he will obtain the facts needed for the solution of
his problem, these are qualities of high educational value whose impor-
tance no one can question. Economic Entomology is full of problems
of every degree of difficulty inviting the student ever onward. It will
be attractive, therefore, to many primarily from the motive of its educa-
tional value, and this motive should influence — indeed, largely shape
the method of study of every student. Do not study for " general infor-
mation," making the mind simply a warehouse for the storing of
miscellaneous facts to no definite purpose, but seek for power to know,
to select, and to use facts.

Economic Value. — Most persons are well aware that the economic
importance of insects is enormous, and look to Economic Entomology for
a relief from their ravages. Some confuse Entomology with Economic
Entomology, and have lost sight of the fact that the latter is a depart-
ment of economics and has to deal primarily with questions of money
values. Whenever the quality or quantity of an agricultural product
is diminished by the presence or activities of insects, it is only in such
cases that we have a problem in Economic Entomology.

The solution of the problems of this science consists in finding ways
and means of avoiding some of the losses due to insects, with, at the
same time, a relatively small expenditure, the index of the success
being the amount of money constituting the difference between cost and
saving secured.

Strive to keep these facts always in mind, endeavoring to develop
sound judgment as to the money value of that destroyed by insects,
and the degree of probability of loss by their future attacks.

HOW TO STUDY.

In this reading course the error one will be most liable to make is to
fail to connect what he reads with his own experience. Every one has
had more or less acquaintance with insects and their work. If one fails
to recognize each of his old acquaintances as he reads about them he
misses by just so much the purpose of this study. The reader should
ask himself as each insect is discussed, "Where have I met this crea-
ture?" And as each fact is brought forth, the further question should
be, "Was this my experience?" Reading in this way, that which
would otherwise be dry and meaningless becomes full of interest.

Further than this the student should begin to observe insects more
earnestly than ever before. Every statement one finds in the books
that he can readily verify he should strive to determine for himself.
Every insect in the field holds something of value to be discovered by
the earnest student. Let one's reading become a key to nature, for it is
nothing apart from nature.

In an attempt to study insects in connection with the reading, the

greatest difficulty that will be met with is the small size of the creatures
studied. A great deal can be learned, even about the smallest forms,
with the unaided eye; but the use of a good hand magnifier will open
ii]) a new world to the student.

How to Select a Magnifier. — Do not choose a lens of large size. The
magnifying power is generally greater the smaller the size of the lens.
For the work proposed in this course we would recommend a f-inch
Coddington lens. This can be obtained through any dealer in optical
goods. In choosing a lens the student should know that freedom from
aberation is the quality most to be sought after. Aberation is of two
kinds, chromatic and spherical.

Chromatic aberation may be detected by first putting the lens very
close to a printed page and slowly withdrawing it. As the letters begin
to lose their distinctness more or less color will be seen around them.
A lens should be rejected if these rainbow colors are very pronounced.

Spherical aberation may be seen when the lens is removed still farther
from the paper, when the letters will appear distinct again, but small
and upside down. Now if the lines are straight and not closer together
at the edges the lens is of good quality in this respect.

How to Use a Magnifier. — After one has obtained a lens he will have
to use it the right way to get the best results. The most important
thing is to see that the point at which one desires to look is in the light.
One must not allow the head or the lens to throw a shadow on the
object and then expect to see plainly.

The next most important thing is to hold all steady. The best plan
is to lay the two hands against each other, one holding the object and
the other the lens, and bring the cheek against the hand, with the eye
as close to the lens as possible.

LIFE HISTORIES OF INSECTS.

Next in importance to the obtaining of that familiarity with the
structure of insects that will enable us to recognize any particular kind,
is an acquaintance with the facts of its growth and development and
with the relation it bears to the season.

Moulting — The most important fact in the structure of an insect is
the hardening of the skin to serve as its skeleton. This makes neces-
sary the process known as moulting, whereby the hardened outer skin
is cast off, so as to permit the enlargement of the body to meet the
necessities of growth. All insects go through this process a number of
times before they become full grown. The detail of the process varies
greatly among the different insects, and may be very different in the
earlier and later moults. If the student has not already observed the
process he should cage a caterpillar in a tumbler, or other convenient

receptacle, providing it with fresh food and keeping it under observa-
tion until a moult occurs. The approach of the moulting period may
be known by the insect refusing food.

Practically all the changes in structure or in the size of the hard
parts of the body are brought about at the time of the moult, and the
change is, therefore, sudden. The most important moult is usually the
last one, for at this time the wings and other adult structures are
perfected.

Metamorphosis. — The change that occurs during the life of an insect,
through its various moults, is called its metamorphosis. We can dis-
tinguish three types of metamorphosis:

1. Primitive, in which the change at each moult is only moderate
in amount.

2. Simple, where the change at the last moult has come to be much
more profound than at any of the others, on account of the develop-
ment of wings. This is often called incomplete metamorphosis, though
the term simple is much more satisfactory.

3. Complex; two moults being required to accomplish the change
from the young to the adult condition, the stage between these two
moults is entirely occupied in accomplishing the reorganization of struc-
ture, and the insect is incapable of taking food during this interval. The
term complete metamorphosis is often applied to this type of transfor-
mation.

The periods of life of an insect are designated as follows:
With Primitive Metamorphosis: egg insect

With Simple Metamorphosis: egg nymph imago

With Complex Metamorphosis: egg larva pupa imago

Annual History. — The possession of metamorphosis permits insects
to adapt themselves so well to the changing conditions of the seasons
that it may be that the seasons are largely responsible for the develop-
ment of this course of life. At any rate, the annual history of an insect,
by which we mean the condition of development of the insect during
the different portions of the year, is the most important study to be
made preliminary to the mapping out of a plan of campaign against
it. How important this matter is may be seen by carefully reading the
account of the vine hopper, the potato worm, the peach worm, and the
codling moth, or of almost any of the injurious insects.

In one's reading and in his study of insects in the field the first work
should be to get a clear idea of the annual history of the insect under
consideration. A good plan is to construct a diagram something like
that given for the peach worm.*

* Bulletin No. 144, p. 32.

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Careful observation in the field during one year should be sufficient
'to gain a fairly complete annual history of an insect, unless it presents
peculiar difficulties. Sometimes it is rather difficult to follow an insect
at a particular season. Some plant lice, for instance, at the period of
migration experience a great mortality, and from excessive abundance
may in a week become so scarce that a very careful search fails to
reveal them anywhere. Perhaps the next spring they may reappear in
an equally mysterious manner and increase to excessive numbers again
by fall.

Possibly some of these cases would become less mysterious if we
made use of cages to confine some of the insects so as to watch the
development so closely that we would with certainty recognize the
insect in all its stages. This is almost essential in the case of insects
with complex metamorphosis, since the change from larva to pupa and
from pupa to imago is so great that one can not safely connect the dif-
ferent stages of the same insect without positive proof.

Any kind of tight receptacle will do for a breeding cage to make
these determinations. Glassware, such as tumblers or lamp chimneys,
will be found very satisfactory for this purpose. Food should be kept
fresh and all the conditions maintained as normal as possible.

CLASSIFICATION OF INSECTS.

The student should make himself acquainted with the classification
of insects, so that he may intelligently follow the literature of ento-
mology, and because the insects belonging to a particular group have
a blood relationship with each other, and the knowledge gained about
one member of a group will be full of suggestions to the student when
he attempts to master another.

Insect Names. — For the purpose of accurately designating insects a
system of technical names has been adopted by naturalists. The full
technical name of an insect consists of three parts: (1) the genus
name, which is usually derived from a Greek substantive, and always
begins with a capital letter; (2) the species name, usually a Latin
adjective corresponding in gender with the genus name, and beginning
with a small letter*; and (3) the authority, an abbreviation of the
name of the original describer of the insect.

Thus one of our commonest grasshoppers bears the name (Edaleonotus
enigma Scud., which might be translated into English as Scudder's
puzzling Swollen-back.

*A common usage is to capitalize those specific names which have been derived from
proper names, but the rule of never capitalizing specific names, as adopted in this cir-
cular, is preferable.

Synonyms. — Unfortunately, many insects have received a number of
names. The rule has been established that the first specific name given*
to an insect, if it does not already belong to another of the same genus,
should always be retained as its true name. Often, however, some one
else may give it another name, either because he did not know of the
first name or because he thought he had a different insect. The new
name, of course, can not hold, even though it may have come into
general use.

Another source of synonyms is the placing of the species name with
the wrong genus name. All the species in a genus should be very
closely related with one another, and if a species is placed where it
really does not belong it must be changed.

Group Names. — A scheme has become generally adopted of indicating
the groups of insects by using a genus name with a special termination;
thus,

Genus, Acridium.

Tribe, Acridiini.'

Subfamily, Acridiinae.

Family, Acridiidsf.
There are several other group-terminations that will be occasionally
met with, but which are not as yet generally adopted.

Orders of Insects. — The primary division of insects is into Orders.
The names of the orders were given before any one had the idea of
using derivative group names. The names of the principal orders end
in -ptera, meaning wing, because Linnaeus, who gave these names,
separated the orders by peculiarities of their wings.

There is much difference of opinion as to how many orders should be
recognized. These differences of opinion are entirely in reference to the
smaller groups. All are practically agreed about the greater orders.
The six large orders are:

Orthoptera = Grasshoppers, etc.

Hemiptera = Bugs, plant lice, scale insects, etc.

Coleoptera = Beetles.

Diptera = Flies.

Hymenoptera = Wasps and bees.

Lepidoptera = Butterflies and moths.
The student should get these six groups thoroughly well fixed in his
mind, so that he can recognize a figure or a specimen of the adult
insect. The structure of the mouth-parts and of the wings should
receive attention. He should also understand about the metamor-
phosis of each group and recognize the young insect.
The minor groups consist of: •

Aptera. Minute wingless insects, now generally recognized as forming a distinct
order ; none are of much economic significance.

Odonata, the dragon flies and damsel flies, aquatic as nymphs and predaceous
throughout their life. Often counted a distinct order, but sometimes united with other
aquatic insects.

Ephemerida, May flies; aquatic forms, which are short-lived and do not take food as
adults. None are of economic importance. Often counted a distinct order, but some-
times united with other aquatic insects.

Plecoptera, the family Perlidss, aquatic insects of no economic importance; are some-
times counted a distinct order.

Forficulidie. The earwigs usually placed with the Orthoptera, but sometimes sepa-
rated by themselves; have subterranean habits and are of but little economic impor-
tance.

Isopoda. The family Termitidse, the white ants, is very injurious in the tropics, but
rarely in the temperate zone. The group is commonly united with the following.

Corrodentia. The family Psocidx, including only insects of no economic importance,
is often considered a distinct order.

Mallophaga. The bird lice are very commonly considered a distinct order, but are in
reality quite close to Psocidee, and might be included in the former group.

Physopoda. These minute insects are the true thrips, and are often highly injurious
to cultivated plants. They are very commonly counted as a distinct order, but are cer-
tainly allied to the Hemiptera and are often included among them. A few authors
place them in the Neuroptera, which is made to include all insects not in the six major
orders.

Pediculida'. The true lice have usually been grouped with the Hemiptera, with
which they are certainly closely allied ; but some authors have united them with the
Mallophaga, and others have made them an order by themselves.

Sialidx. This group of aquatic insects is sometimes made an order by itself and
very generally separated from the Perlidse, on account of having complex metamor-
phosis, though in other particulars it is closely related. The group is not economically
important.

Panorpidse and Hemerobiidix'. These families of terrestrial insects have been made an
order by some entomologists, though commonly classed with the former group, to
which they are near allies. None are injurious; a few may be of some value, on
account of their predaceous habits.

Phryganxidx. The caddice flies are aquatic insects forming a group which has been
given rank as an order by several entomologists, but is often grouped with the preced-
ing. They are of no economic significance.

Pulicidx. The fleas have been made a distinct order by some, though they are closely
allied with the Diptera and classed in that order by most authors.

In the above list the various names which have been assigned to
these minor groups have not been given, but the family names will
enable one to recognize the group in every case.

It will be noticed that the Physopoda are the only insects in this
list which are of any considerable economic importance in California,
and this group can be classed with the Hemiptera. The six larger
groups, therefore, are all we need to seriously study in Economic
Entomology.

INSECTS OF CALIFORNIA.

There are more insects known to occur in California than have been
listed in any other State. The great majority of these are of little or
no economic significance. The really troublesome forms do not form a
very large list. The student should endeavor to gain some knowledge
of all of these. As a guide in this matter the following enumeration of
injurious forms is given:

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Orthoptera.

The insects in this group are mostly vegetable-feeding forms and are
general feeders; that is, none of the species confine their attacks to a
particular plant, as is so common with the higher insects. A fairly
complete account of the more injurious members of the order is given
in Bulletin No. 142; some of the less important forms are discussed in
the reference books. The injury these insects do to plants si so evident
that it is comparatively easy to estimate the amount of loss resulting
from their attacks. One family, the Mantidae, is predaceous and has
figured to some extent in the schemes of introducing beneficial insects
to attack injurious ones.

Hemiptera.

The interest in this group centers mainly around the scale insects
and plant lice, though most of the members of the order are also plant
feeders and several forms are highly injurious. A few bugs are pre-
daceous, but have attracted very little attention.

All the vegetable-feeding forms obtain their food by sucking the juices
of plants, and it is very difficult to determine in any particular case the
exact amount of injury to be expected to result from an attack. Up
to a certain point the presence of a sap-sucking insect amounts to
nothing, and when the general vigor of a plant is good and the con-
ditions otherwise favorable, a plant can stand without appreciable
injury what would in other cases be fatal to it.

One must take into consideration the moisture condition of a plant
as well as the numbers of the insect present.

Another factor which complicates the problem is the sporadic increase
and decrease of these insects which is often noticed. Many of them are
capable of increasing with incredible rapidity when conditions are
favorable. Since we do not know exactly what these conditions are
it is hard to say whether the insect in question will reach injurious
numbers or not. Again, under other equally unknown conditions not
only the fecundity may suddenly diminish, but the life of a greater part
of the individuals may be lost and the whole economic situation be
changed. The student should observe with greatest care the evidences
of changes of this kind, and may be able to add materially to the
knowledge of the subject. At any rate, he should get enough acquaint-
ance with these phenomena to cause him to exercise due care in coming
to conclusions in regard to the action of insecticides or of any other
means of control that may be adopted. A very good experiment which
will show the effect of external conditions upon these insects may be
made by covering the top and three sides of an apple tree with mos-
quito netting and comparing effect on the woolly aphis as contrasted
with adjacent trees in the orchard.

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Physopoda. Some of the reference books give a very good general
account of these insects, but there has been very little done experiment-
ally toward their control. Those favorably located for making observa-
tions on the life history of these insects, especially their wintering habits,
or on the application of insecticides, can make real additions to our
knowledge of the subject.

CoccidcY, or scale insects, have done a great deal of injury in this
State, and the San Jose scale is one of the best known injurious insects
in the United States. The reference books give a particularly full
account of this insect and of experimental work for its control. This
subject deserves very careful study. Besides the San Jose scale (Aspid-
iotus perniciosus Corns.) we have in California the closely allied greedy
scale (A. rapax Corns.) and the oleander scale {A. hedrese Vail.), with
much the same habits, but hardly as injurious, and also the red scale
(Chrysomphalus aurantii Mask.) of the orange. The long scales, the
oyster-shell scale (Lepidosaphes ulmi Linn.) of the apple and the purple
scale (L. beclii Newm.) of the orange, are really also quite similar in
habits to the above.

Another kind of scale is represented by the black scale (Saisetia olesc
Bern.), the soft brown scale (S. hesperidum Linn.), the brown apricot
scale (Eulecanium armeniacum Craw), and the pruinose scale (E. prui-
nosum Coq.). They are rather better protected from sprays when full
grown and more easily killed when young than the scale insects
formerly enumerated. The development of the smut fungus in the
excretia of these insects gives them additional means of doing injury to
fruits and ornamental plants.

The cottony cushion scale (Icerya purchasi Mask.), which is usually
controlled by the imported ladybird, Vedalia cardinalis, forms a group
quite by itself.

Aleurodidse, or white flies, are of interest chiefly because of the possi-
bility of the introduction of the injurious orange species of Florida, as
none of the local species are particularly injurious. One of the green-
house species is discussed quite fully in the reference books.

Aphid x. Plant lice are next to the scale insects in the amount of
injury produced. Each of the important species presents problems
peculiar to itself, and the Eastern accounts of these insects will often
not apply to the same species on this Coast.

The grape phylloxera (Phylloxera vastatrix Pla.) is the only species
discussed in the bulletins of this Station, and is the most injurious
insect of this group in the State. The woolly aphis (Schizoneura lani-
gera Haus.) stands next to the codling-moth as the most injurious apple
insect. It is entirely different from the phylloxera in habits and
character of injury, but like the latter is best controlled by the use of
resistant roots.

n

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Other important species are the hop aphis (Phorodon humuli Sch.),
the grain aphis (Nectarophora avenae Fabr.), the cabbage aphis (Aphis
brassicae Linn.), and the black peach aphis (Aphis persicae niger Sm.).
These will be found discussed from an Eastern standpoint in the refer-
ence books.

Cicadina indicates a number of families of mostly minor importance,
but in the family Jassidtr, the leaf hoppers, there are a considerable
number of important forms. They mostly attack grasses. Two spe-
cies have done injury to grapevines in this State, one of which, the
vine hopper (Typhlocyba comes Say.), is very troublesome. It is dis-
cussed in Bulletin No. 116.

Heteroptera includes the greater part of the larger members of the
order. There are several families represented, including all the preda-
ceous forms, several of which became famous a few years ago under the
name "kissing bugs." There is only one member of this series of fami-
lies that may be considered an injurious insect of first class, producing
millions of dollars of loss in a single year. It is the chinch bug (Blis-
sus leucopterus Say.), and will be found fully discussed in the reference
books. This is an interesting case for the economic entomologist,
because while it has been known on this Coast for years it has never
done any damage, so far as can be learned.

We have several injurious species belonging to this group, but the
only ones to attract much attention are the Harlequin cabbage bug
(Mnrgantia histrionica Hahn.) and the squash bug (Anasa tristis Del.).

COLEOPTERA.

The beetles include nearly half of the known insects, but there is no
large number of injurious species. The habits of the different mem-
bers of the order are very diverse and must be considered group by
group.

The Clavicomia include a large number of families of beetles, most
of which feed on decaying substances. None of the California repre-
sentatives are known to injure growing plants except some of the lady-
birds (Coccinellidse), and these only occasionally and to a slight extent.
The usual food of the ladybirds consists of plant lice and scale insects,
and are considered the most beneficial members of the entire order.
Some Clavicomia are very troublesome pests in the house because of
their feeding on furs, woolens, etc., and one species (Sylvanus surina-
mensis Linn.) does injury to stored grain and to dried fruits.

The Phytophaga are all vegetable feeders. The family Bruchidae
includes the pea weevil (Bruchus pisorum Linn.) and the bean weevil
(B. obtecus Say.), both of which are injurious in this State as in the
East. The family Chrysomelidx contains the flea beetles, various
species of Phyllotreto, Epitrix, and Haltica, and the notorious Diabrotica
soror Lee. Many other species are occasionally locally troublesome.

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The wood borers (Cerambycidse) are abundant in some parts of the
State, and injurious to forest and shade trees; but only one — the large
Prionus califomicus Mots. — has attracted much attention as attacking
fruit trees, and this only locally.

Rhynchophora, or snout beetles, are well represented on this Coast,
and though they are practically all plant feeders, scarcely any have
attracted the attention of horticulturists. Two closely allied species?
Calandra granaria Linn, and C. oryzse Linn., the grain weevils, are
well known by their work in stored grain. Several species of the family
Scalytidae have done very destructive work on forest and shade trees.

Serricornia include a rather heterogeneous series of families. The
wireworms (Elateridm) are occasionally destructive to the roots of
truck crops, but what species are accountable for the damage has not
been ascertained. Of the BitprestidcT, the " flat-headed " borer ( Chrysobo-
thris femorata Fab.) easily takes first place. It deserves a great deal of
careful study, since the Eastern recommendations do not appear to
suffice in this State. This and other species sometimes do considerable
damage to forest and shade trees. Several of the Lampyridae feed on
plant lice, and none of the family are injurious. The only other serri-
corn beetle to come into prominence is one of the Ptinids?, Polycaon
confertus Lee, which bores holes into olive twigs. The larvae feed
within the stumps of grapevines.

Heteromera are unusually well represented in California, but with
comparatively few injurious forms, practically all of which belong to
the family Meloidse. These are known as blister beetles. They are
only occasionally present in destructive numbers.

Lamellicornia include a number of mildly injurious insects. The
adult of several species of Serica and Hoplia have attracted consider-
able attention by eating the leaves and buds of fruit trees.

Adephaga are practically all predaceous.

Diptera.

The flies are probably the least studied of the larger orders. Many
of the species are very minute, and the great majority live on decaying
vegetable matter and have no economic significance.

The Cecidomyidse include the Hessian fly (Cecidomyia destructor Say.)
that sometimes does some injury to grain in the Bay region, but is far
from being the pest it is in the Eastern States.

The Tipulidm contain a few species that occasionally give some
concern to truck farmers. The larvae are called leather-jackets, and
sometimes injure the roots of plants. Which species are concerned has
not been determined. Several families contain blood-sucking species.
Some are predaceous and others parasitic.

There are numerous fruit flies in other countries which may ulti-
mately reach here and revive the interest in this order.

13 —

Hymenoptera.

The most important group in this order is that including the saw-
flies. Two species are well known to fruit-growers: the slug of the
cherry and pear (Eriocampa cerasi Peck.) and the green caterpillar of
the pear (Gymnonynchus calif 'ornicus Marl.), the latter being peculiar
to this State, but having much the same habits as the other, which is
found all over the United States.

The horntails (Siricina) and the gall wasps (Cynipina) attack mainly
forest and ornamental trees, but are rarely injurious.

The joint worm of wheat (Isosoma tritici Riley) occasionally does a
little damage. The family to which it belongs, and all the related
forms, are parasitic.

Some of the wasps and the honey bee are troublesome on ripe fruit
and on the drying grounds, and the honey bee is charged with sys-
tematically spreading the dreaded pear blight.

Lepidoptera.

The larvae of Lepidoptera are almost exclusively plant feeders, and
include a large part of the injurious species attacking cultivated plants.
They are nearly all controllable by the use of arsenical sprays, so that
we may say that on the whole they are better controlled than most
other pests.

Tineina include a large number of small moths, a few of which are
troublesome in the house; such as the clothes moth (Tinea pellionella
Linn.), the Mediterranean flour moth (Ephestia kuehniella ZelL), and a
number of others. Those most injurious to plants are the peach worm
(Anarsia lineatella ZelL), the potato worm (Phthorimsea operculella
ZelL), the codling moth (Carpocapsa pomonella Linn.), and the peach-
tree borer (Sanninoidea opalescens Edw.), all of which are discussed in
the bulletins of this Station.

Bombycina average larger than the moths of the preceding group,
and include over half of the members of the order. One of the larger
families of this group is the Geometridse. The larvae of these moths
walk by "looping," and are often called inchworms. The most in-
jurious member of the family is the cankerworm (Paleacrita vernata
Peck.). The Noctuidse is the largest family of moths. Many species
are highly injurious, especially the groups known as cutworms. There
are quite a number of species representing several genera. Only in a
comparatively few cases have our species been bred to the adult con-
dition so that they could be determined. Therefore, we do not know
how many species are really involved.

The S alumina are our largest moths, but do not include any that
are highly injurious.

The Sphingina, or hawk moths, include the tomato or tobacco worm

— 14 —

(Phlctjcthontius sexta John.), and the so-called armyworm of the grape
(Pholus arJirmon Drury).

The Rhopalocera, or butterflies, are not generally injurious; the cab-
bage butterfly (Pontia rapse Linn.) being an exception.

ACARINA.

Besides the true insects, this class of animals, more nearly allied
to the spider, is usually considered to belong to the domain of the
economic entomologist. They are all very minute creatures, appro-
priately called mites; some of which attack plants and produce injury
much like that produced by insects.

Phytopti are excessively small creatures, and include the rust mites
of the orange (Phytoptus sp.), the erinose of the vine (Phytoptus vitis
Land), and the blister mite of the pear (Phytoptus pyri Nal.), all strik-
ingly different from each other in the appearance of the affection they
produce on the plant they infest.

Tetranychi, or red spiders, are still more injurious. There are various
species of Tetranychus and Bryobia, usually confused with each other.
One species of each of these genera is discussed in the bulletins of this
Station. Much remains to be done before the other species are as well
known.

INSECT CONTROL.

The means that may be adopted for the prevention of injuries due to
insect attack require as careful study as the insects themselves. The
student should observe with the greatest care the action of insecticides,
and in every experiment arrange checks, that is, untreated trees or
branches, where every condition will be comparable with the treated
trees.

Many valueless materials are sold as insecticides, and the dealers are
able to obtain an unlimited number of testimonials from honest men
setting forth the effectiveness of their nostrum. The importance of
caution and scientific accuracy in observations of this kind can not be
too strongly insisted upon.

Diseases. — Attention has already been called to the great oscillations
experienced by some species of insects. In many cases the cause of
this can be quite definitely laid to the effect of fungous or bacterial
diseases. Many have speculated upon the possibility of using these
diseases for the control of injurious insects, and in a few cases consider-
able progress has been made. In the case of the chinch bug, for
instance, an insect for which no ordinary insecticide is available, there
have been notable cases of the most complete success with this method.
It is considered a thoroughly unreliable method, however, because sue-

— 15 —

cess depends entirely upon the occurrence of favorable atmospheric
conditions, which are entirely beyond our control. When these condi-
tions occur the diseases commonly appear spontaneously without our
assistance.

For these reasons, very little attention is now being given to this
subject,

Parasitic and Predaceous Insects. — A method of control which has
always been looked upon with a great deal of hope is that of using
the natural insect enemies of the injurious species. From the
earliest beginnings of economic entomology, much attention has been
given to the study of parasites and predaceous insects. Various meth-
ods of favoring these insect allies have been proposed and tried, with
no very flattering results until a large number of Australian insects
collected by Messrs. Koebele and Webster were introduced into the
State in the hope that something might be done to aid in the fight
against the cottony cushion scale. One of these, a ladybird ( Vedalia
cardinalis) , more than fulfilled the expectations of those concerned in
its introduction. This success resulted in greatly extended efforts along
this line. Mr. Koebele and our State Board of Horticulture have been
untiring in their work in this direction, and while no such success as
that with the Vedalia has followed their efforts, still the work is one
deserving much more attention than has yet been given to it.

From the nature of the problems involved, it can not be undertaken
profitably by individuals, but requires the expenditure of a great deal
of money.

There has been much very unreliable matter printed concerning this
subject, and the most extravagant statements have been made concern-
ing insects of very ordinary degree of effectiveness. It requires the
most careful and painstaking observations before any one is competent
to speak intelligently in reference to the effectiveness of an introduced
insect,

Resistants. — A third method of combating insects, which is looked
upon with a great deal of expectancy, is the selection or development
of plants upon which insects can not or will not feed. Every one has
noticed plants distasteful to insects and which remained untouched
while those all around have been injured by them. In two notable
instances this has been made use of with the best of results. We are
only at the beginning of work along this line and can only guess what
may be brought forth by careful and systematic investigations.

Remedies. — While the preceding control-methods may wisely receive
the attention of those in position to study them, that with which the
individual grower can most profitably concern himself is the use of

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chemical insecticides. This subject, however, need not be discussed in
the present circular, since it is so fully treated in Circular No. 7 of this
Station.

CONCLUDING REMARKS.

The purposes of this course will be largely fulfilled when the student
obtains sufficient acquaintance with the facts, and such an appreciation
of the difficulties of accurate observation that he shall approach a
problem with such a scientific, conservative spirit that he will not be
misled by appearances, unsupported by definitely ascertained facts.
Whether or not this will be accomplished depends, in a reading course,
upon the individual reader; since he will not have the assistance of the
teacher's personal contact. This may be partly compensated for, if one
is a member of a reading circle, by discussions with the other members
of the circle. Not a little help will come from trying to put one's
impressions into writing. For this purpose the following set of ques-
tions is given with the suggestion that each reader carefully write out
answers to each question, following his reading on each subject. A
comparison of the answers written out by different members of the
circle will be profitable. This set of questions is the one used in the
Course on Economic Entomology at Berkeley, last term. They were
placed in the hands of the students just before the examination and
the questions actually given were chosen by lot from this list:

Questions foe Course in Entomology — Agr. lb.

Scale Insects.— (1) Give scientific names of the black scale, and explain construction
of such names. (2) Describe structure of black scale. (3) Describe mouth parts, and
explain manner of feeding. (4) How are scale insects distributed from plant to plant.
(5) Point out the difference in structure between black and San Jose scales. (6) Give a
general account of distillate spraying; (7) of resin soap, and lime, salt, and sulfur mix-
tures; (8) of cyanide fumigation. (9) Discuss the use of parasites and predaceous
insects as a means of control.

Other He mipter a.— (10) Give a general account of the woolly aphis ; (11) of the phyllox-
era; (12) of the use of resistant roots. (13) Give method of control of leaf-inhabiting
plant lice. (14) Describe injury done by the vine hopper. (15) Give its life history.
(16) Explain difficulties in killing it.

Fruit Worms.— (17) Describe egg-laying habits of codling-moth. (18) Process of hatch-
ing and entering the apple. (19) Describe the pupation. (20) Discuss the use of bands
for codling-moth. (21) The method of spraying with paris green. (22) Give winter
habits of the peach worm. (23) Explain theory of spring treatment with lime, salt, and
sulfur. (24) Describe summer treatment for peach worm.

Other Lepidoptera.— (25) Give life history of the peach-tree borer. (26) Discuss the
gumming of the peach trees. (27) Describe the digging-out process of treatment.
(28) Discuss precautions in the use of carbon bisulfid. (29) Give general account of cut-
worms. (30) Discuss the remedies for cutworms. (31) Give the remedies for canker-
worms.

Grasshoppers. — (32) What is meant by the breeding-ground of migratory grasshoppers?
(33) Distinguish between the migratory and non-migratory grasshoppers. (34) What
remedies are available on the breeding-grounds? (35) Describe the construction and use
of the hopper-doser. (36) Give an account of the use of poisoned bait for grasshoppers.

— 17 —

Hymenoptera and Diptera. — (37) Give the life history of a sawrly. (38) Explain method
of treatment. (39) Describe life history of Hessian fly. (4(t) Methods of preventing its
injury. (41) Describe the life history of fruit maggots ; (42) of leather-jackets.

Coleoptera.—{$&) Discuss means of control of white grubs; (44) of wireworms;
(45) of borers.

Mites.— (46) Give the life history of the almond mite; (47) of the red spider of citrus
trees. (48) Explain the effect of sulfur sprays.

INSTRUCTION IN ENTOMOLOGY AT BERKELEY.

For the information of those who desire to continue their studies in
Entomology at the University, the following statement of the work
offered in this department in the Summer Session, Short Course, and
Regular Session, respectively, is appended:

In the Summer Session, July to August, the following work is designed
primarily for teachers of nature study in secondary schools:

1. Indoor Nature Work. Lectures and demonstrations illustrating
the study of insects in the class-room.

2. Important Insects. Lectures upon those insects which most con-
spicuously affect the interests of man.

3. Outdoor Nature Work. A series of excursions for the study of
insects in the field.

4. Classification of Insects. This course is designed to acquaint the
student with the methods of finding the names of insects and to
acquaint him with the literature of the subject.

5. Methods of Microscopical Study. Designed particularly for
advanced students or those owning their own microscopes; a drill in
the method of mounting and microscopical observations.

The Short Course in Agriculture has not been arranged for the
coming autumn. The work in Entomology offered last fall consisted of
a course of lectures on Economic Entomology and a laboratory course
on Scale Insects. A special announcement can be had upon applica-
tion next August.

The Regular Session work is as follows:

4A. Agriculture. The insects affecting field crops are discussed in
connection with their cultivation.

4B. Horticulture. The insects affecting the various fruit crops are
discussed as each fruit is considered.

5D. Viticulture. The insect pests of the vine are fully treated of in
this course.

7A. General Entomology. A rapid review of the classification,
structure, and habits of insects.

7B. Economic Entomology. Review of the insects most injurious to
agriculture in California.

7C. Ecology. The relation of insects to their environment. A dis-

— 18 —

cussion of the newer lines of thought concerning the evolution of
insects.

7D. Apiculture. Practical review of the methods and problems of
modern bee keeping.

8A. Morphology of Insects. A laboratory study of insect structure,
including careful drawing and dissection of a series of typical insects.

8B. Scale Insects. Detailed study of the structure and classifica-
tion of scale insects, and the methods of using the compound microscope.

8C. Entomotaxy. The methods of collecting, mounting, and deter-
mining insects.

8D. Apiary Work. Actual handling of bees under apiary conditions,
and experiments with bees in observation hives.

9B. Insecticides and Fungicides. The composition and compound-
ing of remedies.

9C. Spraying. A study of the methods of spraying plants for the
control of insect pests and fungous diseases.

11A. Ontogeny of Insects. A detailed study of the genesis of the
insect structure.

11B. Phytogeny of Insects. The genealogy of insects and the study
of classification in the light of evolution.

12. Advanced. Laboratory Work. Each term a different line of
advanced study will be offered in this course, and individual work will be
arranged for those desiring to begin research work.

23A. Entomological Literature. A seminary course for conference
between students engaged in bibliographical study.

23B. Laboratory Conference. A seminary course prescribed for all
students taking Courses 12 or 24, designed for mutual assistance in the
work under way in the laboratory.

24. Research Work. Individual investigation under the direct
supervision of the instructor, but not necessarily at Berkeley nor in
term time. Credit will only be given on the basis of work ready for
publication.

liu

UNIVERSITY EXTENSION IN AGRICULTURE.

The Department of University Extension in Agriculture has here-
tofore confined itself to Farmers' Institutes. With this publication
it begins work of a somewhat wider scope. The College of Agriculture
and the Agricultural Experiment Station have from the beginning-
striven to serve the people in every part of the State, and, while pro-
viding laboratories at Berkeley for the study of agricultural problems,
and class rooms where the young people of the State may come for
instruction, they have also endeavored to extend their influences into
every community. These efforts may be grouped into the following
classes:

1. Correspondence with individuals in answer to requests for infor-
mation on agricultural problems.

2. Publications, based on studies made by members of the Station
staff. These are sent free of charge to residents of the State applying
therefor.

3. Lectures before public meetings: Farmers' Institutes, or other
gatherings representing agricultural interests.

4. Reading Courses, like that outlined in the present circular.

5. Personal Visits by members of the staff to regions where problems
of great importance arise.

6. Cooperative Experiments, conducted by individuals, working
under the advice and generally the personal supervision of a member
of tne Station staff.

7. Investigations, involving the residence for some time of a repre-
sentative of the University in the locality where the problem in hand
may be best solved.

8. Substations, which are established in regions where there is a
variety of problems, requiring years for their solution, making a rather
permanent equipment necessary and the continuous residence of a Sta-
tion man.

To this list should be added the increasing number of graduates of
the Agricultural College, who are farming in many parts of the State,
and who should be and who are centers of influence for University
ideals.

The location of the College and Station at Berkeley has been fortu-
nate in that it favored the development and this broad conception of
their opportunities and duties toward the State at large.

Printed at the State Printing Office, W. W. Shannon, Superintendent.