The Ohio
Journal of Science
DECEMBER,
Volume XVI.    1915    Number 2.

(Continuation of The Ohio Naturalist)

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and of the

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THE

Ohio Journal of Science

PUBLISHED BY THE
Ohio State University Scientific Society

Volume XVI   DECEMBER, 1915   No. 2

TABLE OF CONTENTS

Wells—A Survey of the Zoocecidia on Species of Hicoria
Caused by Parasites Belonging to the Eriophyidæ
and the Itonididæ (Cecidomyiidæ)  [37]
West—The Geometry of the Translated Normal Curve[60]
Gibson and Cogan—A Preliminary List of the Jassoidea
of Missouri, with Notes on Species[71]
News and Notes[79]

A SURVEY OF THE ZOOCECIDIA ON SPECIES OF
HICORIA CAUSED BY PARASITES BELONGING
TO THE ERIOPHYIDÆ AND THE ITONIDIDÆ
(CECIDOMYIIDÆ).[1]

Bertram W. Wells.

This paper is primarily an attempt to present adequate descriptions of the types of 30 itonid (cecidomyid) and 2 eriophyid (mite) galls, collected by the writer on hickory leaves. It is believed to contain sufficient new material to warrant its publication in advance of a general survey of N. E. United States zoocecidia, of which it will form a part. The data is based on collections made in Connecticut, Ohio and Kansas, most of the material however, being taken in Ohio.

In addition, those forms (few in number) previously described which have not been seen by the author, have been added, so as to give a character of completeness to the survey of the two groups of galls.

There are three groups of zoocecidia occurring on hickory trees:

1. Galls formed by species of Eriophyes (Fam. Eriophyidæ of the Acarina or mites), or an allied genus. Only two are known.

2. Galls induced by species of Phylloxera (Aphididæ of the Hemiptera). Pergande[2] has presented an excellent survey of these insects accompanied by very satisfactory descriptions of the cecidia formed by them.

3. Galls caused by species of Caryomyia (Itonididæ of the Diptera). Possibly other genera may be represented on the hickories, but according to Felt[3] “most of the hickory leaf galls are probably made by species of Caryomyia, though other midges have been reared from these deformities.”

The genus Caryomyia, which undoubtedly occupies an important place in relation to the majority of the galls described in the present paper, will be given special consideration. Felt, to whom American cecidology is heavily indebted for his extensive studies of dipterous cecidozoons, presents the following description of the genus Caryomyia in the same citation as that immediately above.

“Allied to Hormomyia, but differing by the thorax not being greatly produced over the head and by the presence of but 14 antennal segments. The males may have the flagellate antennal segments binodose or cylindric and subsessile and invariably with three low, stout circumfili. The antennal segments of the female are cylindric and with two circumfili; palpi tri- or quadri-articulate; wings rather broad, the third vein joining the costa at or near the wing apex; claws simple, the pulvilli well developed. The ovipositor of the female is short and with minute lobes apically. The genus appears to be confined to hickory leaf galls.”

Adult insects not technically known are given the old generic name “Cecidomyia.”

These galls as well as similar ones on other kinds of plants arise as the result of some stimulus (the nature of which is still not definitely known) applied by the very young larva to the growing tissue of the immature leaf. Nothing has yet been done on the development of the itonid galls of the hickories, but from studies on very similar types we have reason to believe that the ontogeny of the itonid forms is as follows: The egg is probably deposited superficially (for the ovipositor of the female Caryomyia is short) on the under side of the leaflet; on the upper side in a few cases.

Hyperplasia or excessive cell proliferation results (probably not until after the larva has emerged from the egg) forming at first a saucer-shaped structure, then cup-shaped and finally by the ingrowth of the edges, the gall becomes a closed structure enveloping the larva in a chamber. The distal growth, seldom if ever in the hickory forms, proceeds so far as to obliterate the opening which was so prominent in the very immature cup-shape stage. Hence in practically all galls of this type a minute canal or pore can be demonstrated at the distal end. In Küster’s[4] very serviceable classification of abnormal plant parts, these fall under his “umwallungen” cecidia, a term very succinctly describing their mode of development.

Two of the following described galls have been studied histologically by Cook,[5] Caryomyia holotricha O. S. and C. tubicola O. S.

Concerning the problem of the distribution of the galls on the different species of hickory, it is still too early to be able to make any positive assertions. In most of the reports the species of tree has not been given. It is very well known that certain species of galls are found on 2 and 3 species of hickory, but whether they are developed on all indiscriminately is not known. H. cordiformis seems to bear much fewer species than H. ovata or H. alba. In the present list, the report of the gall upon a particular species of tree does not at all imply that it does not occur on others.

Having had the opportunity to give attention to gall collecting in three rather widely separate localities, eastern Connecticut, southern and northern Ohio and eastern Kansas, some observations on the geographical distributions of the hickory itonids are here briefly presented.

It is sometimes stated that the distribution of gall insects is similar to that of their host plants. In certain cases this does not seem to be true. In that of my number 32 first found and described by Sears, no report of this large and striking form has appeared, showing it to occur east of the Allegheny mountain system, a region in which H. ovata is abundant. In the cases of my numbers 5, 9, 19 and 31, all heretofore unreported and possessing prominent distinguishing characters, it would seem as though they were somewhat restricted in their distribution, for while comparatively common in Ohio, they are never seen in Connecticut or Kansas, where equally intensive collecting was prosecuted. So few are the students of cecidia and so meager the data in this field, that it is, however, much too early to make positive assertions in matters of geographic distribution.

The data on the galls presented herewith was compiled for the most part at the time of collection; the notes and drawings made from fresh material. For later comparative work, the material was all preserved in formalin, each collection being assigned to a vial.

The writer has refrained from attaching a specific name to his new species of cecidia, a practice very common on the part of European cecidologists. Even though the adult gall has no direct relation to the adult insect, the fact, nevertheless, remains that the specificity of the gall owes its origin to the specificity of the physiological phenomena of the larval insect, and it is this, which in the mind of the writer, gives pre-eminence to the insect. The adult gall and the adult insect can be conceived as arising from the same complex, the larva, the adult insect bearing, however, a more intimate and direct relation to the original source of events than the gall. In many cases the adult insects offer characters, making possible the delimitation of species, with greater exactness, than do the galls. For these reasons new names of cecidia should only appear with adequate descriptions of the cecidozoons.

Though the galls almost uniformly occur on the under side of the leaflet, the drawings have presented them in an inverted position, with the gall uppermost, this being the position in which the galls would be examined. In practically all cases there are two sketches of the type, one showing the exterior aspect of the gall, the other the interior as seen in a vertical, median section. The figure number is in all cases the same as the list number.

The writer wishes to express his appreciation of the hospitality of his friend, J. L. King, who, as assistant entomologist for the Ohio Experiment Station, shared his field laboratory during some of the time in which cecidological collecting was being carried on.

Though the writer has seen (with a few exceptions) the types herewith detailed an amply sufficient number of times to establish them as types, he does not claim infallibility, for the key he has worked out to these types. It is hoped, however, that it, together with the descriptions and illustrations will enable the student of the hickory galls to become better acquainted with the members of the two groups treated.

Britton and Brown’s Illustrated Flora Northern U. S. and Canada, (2nd edition), New York, 1913, has been followed in the matter of plant nomenclature.

The following two galls whose makers have been named by Felt have probably not been seen by the writer. Felt’s descriptions are given. They are not included in the key.

Caryomyia thompsoni Felt.
“Globose, thin-walled, long haired, melon-shaped, dia. 2-3 mm.”
See my number 23.

Caryomyia antennata Felt.
“Globose, thick-walled, yellowish green or brown. Dia. 4-5 mm.”

This description, as far as it goes, would indicate a similarity to C. persicoides Beut.

Felt, Jour. Econ. Ent. 4:456. 1911.