17G 
Ohacrvations on the various Insects 
as soon fis the foliage produces no more sap. Another species of 
aphis is found in October on the roots,* and being of an 
ochreous or pale yellow colour, it is not easily detected. Tlie 
only specimens I have seen were small, apterous, and mealy, as 
such subterranean species generally are. They had 2 short horns 
and G short stoutish legs. 
The Rust. 
This disease, which so materially affects the carrot crops and 
deteriorates their value, is occasioned in the first instance by 
the larvc© of a small fly. These maggots eat passages in the tap- 
root, as exhibited in PI. T, fig. 1, and the carrots gradually die 
off, changing to an ochraceous or ferruginous colour where they 
have been eaten, whence they are termed " Rusty " by cultivators, 
and they become of little value; for the fibrous roots perishing, or 
being arrested in their growth, from a want of free and healthy 
circulation, the plants sicken if they do not immediately die : they 
lose their saccharine qualities, are consequently no longer sweet 
to the taste, and eventually they become black and rotten, espe- 
cially when stored. The flies and their maggots are found 
through the summer, and the latter even in the winter, but they 
leave the roots to become pupa; in the earth, in which state they 
remain until the spring, but the summer broods hatch in three or 
four weeks. 
On digging up some carrots in a clay soil the end of Decem- 
ber, 1844, which were small and crowded from having been neg- 
lected, I found a considerable number of them maggot-eaten or 
rusty. On the tops were small black slugs ; white Podura^t were 
also running out and into the cavities, and towards the apex of 
the roots large excavations were made, as represented in the plate 
(fig. 1), whether by slugs, worms, or millipedes, I cannot say. 
The most remarkable appearance, however, was occasioned by 
Avhitish, shining, conical objects sticking out of the sides horizon- 
tally, sometimes projecting nearly a quarter of an inch (fig. 2, 2). 
I soon saw they were maggots, which on being exposed to the 
light often withdrew themselves into the holes they had made in 
the carrot, and on dividing these longitudinally, various labyrinths 
were exposed, some of which entered the very heart of the root 
(fig. 3) : these cavities were dirty and brown, which colour was 
suffused to a considerable extent. 
The maggots are ochreous and shining, cylindrical, pointed at 
the head and obtuse at the tail : they resemble cheese-hoppers, 
* 'Entomologist,' p. 127. ' 
•I- They are little skipping animals, thus named by Linnaeus. Vide Curtis's 
'Guide,' Genus 4. 
