282 OBSERVATIONS ON INSECTS. 



to be a dwarfed variety of the common jointed rush 

 (Juncus articulatus), but which is in fact the nidus 

 of a peculiar insect, known to entomologists by the 

 name of Livia juncorum. The larvae of this insect, 

 when hatched, feed upon the juices of the plant, the 

 supply of which is increased by a greater determin- 

 ation of sap to the particular part punctured by the 

 parent in laying its eggs ; and the plant in conse- 

 quence becomes monstrous at that part, producing 

 compact leafy bunches, instead of stalks and flowers. 

 If these be opened, they will be found full of the 

 larvae and pupae ; and by gathering them, and keep- 

 ing them in a box for a few days, the perfect insect 

 may be reared without difficulty. The latter appear 

 about the second or third week in September.* 



The galls, which occur so abundantly on oaks in 

 the spring, as well as on other plants, are familiar 

 instances of an analogous diseased growth of particu- 

 lar parts from the attacks of insects. Tubercles of a 

 peculiar form may also be observed occasionally on 

 the Scotch and spruce firs, very much resembling 

 young cones, but which on being cut open are found 

 to be the nest of a species of Aphis .^ 



* The first notice of this insect, so far as I am aware, by any 

 English naturalist, will be found in the Linnean Transactions, 

 (vol. ii. p. 354,) where there is also mention of the peculiar mon- 

 strosity which it occasions in the Juncus articulatus, and which 

 was actually considered as a viviparous variety of that plant by 

 Linnaeus. Since then, both the insect and its nidus have been 

 figured by Mr. Curtis in his British Entomology, (pi. 492,) to 

 which work I refer those who desire further information respect- 

 ing them. 



t For notices of many other gall-like excrescences on plants 



