PSYCHE. 



THE ENTOMOCECIDIA. 



Introduction. 



BY FERDINAND AXTOX FRANZ KARSCH, BERLIN, GERMANY. 

 [Translated by B : Pickin.in M.lnn, from Entomologische nachrichten, July 1SS4, jahrg. 10, p. 205-209.] 



I propose to offer, under the above 

 title, witliin the next few years, a list, 

 arranged by families according to a 

 zoological system, of the galls (cecidia) 

 which are produced on plants by insects 

 (entoma), so far as such a list will serve 

 to fill up gaps now existing. The cate- 

 gory "plant-galls" is to be taken in the 

 widest sense of the word, i. e., it is to 

 embrace all those modifications which 

 lie outside of the normal methods of 

 development of the plant, and which are 

 presumed to be due to the influence of 

 a definite insect in any stage whatever 

 of its development, from the egg to the 

 imago. Usually onlv those vegetal for- 

 mations are designated by the term 

 "galls," which, while they do lie outside 

 of the normal structure of the plant 

 under consideration, yet show forms so 

 definite and so perfect in themselves that 

 they might rather be spoken of as an 

 ornament than as a pathological phe- 

 nomenon of growth. Of this kind are 

 the well-known puft-balls of our oaks, 

 the bedeguars of our roses, and the spi- 

 rally twisted petioles of our poplars. 

 But a wider knowledge of such forms, 

 and the observation that anomalies 

 which are far less obvious, and there- 

 fore are usually overlooked by the lait}'. 



are due to exactlv the same formative 

 impulses (such, for instance, as the 

 crumpling of the leaves of trees b}' the 

 suction of certain apkididae), vaaVc it 

 necessary to broaden the category 

 "galls," and now every creative reaction 

 of a part of a plant against an irritation 

 which aflects it, whether proceeding 

 from an animal or a plant, is concei\ed 

 of as a gall-making activity, and the re- 

 sultant structure (cecidinm) is termed a 

 mvcocecidimn if a fungus figures as the 

 impulse of the pathological formation, 

 and as a zoocecidium if it is due to an 

 animal. 



If a coleopterous larva devour the 

 parenchyma of a leaf, or a caterpillar 

 spin together the margins of the leaves 

 in order to make itself a shelter and to 

 prepare itself a closed storehouse for 

 food, the inhabited part of the plant 

 opposes no obstacle to the doings of the 

 animal, and the "miners" are very well 

 to be distinguished from the cecidozoa. 

 Bladder-galls, on the contrary, arise in 

 another way, when the parenchj'ma of 

 the leaf increases instead of becoming 

 less, and the aflected place thickens ; 

 and cecidia arise when leaves of trees 

 expand in a direction other than the 

 usual one, solely because of the irrita- 



