Insects, etc., Injurious to the Plum. 



395 



parts of Britain in 1906 showed the extraordinary parasitic Procto- 

 trupids of the genus Aphelopus. The infected individual looks as 

 if its abdomen were bifurcated, for the "gall" produced by the 

 parasite equals or rivals in size the abdomen of the host. 



These "galls," for they are nothing more or less than animal 

 galls, have been previously noticed by Giard (7) in France, and he 

 speaks of them as " Thylacia." These growths are formed by a 

 gradual dilatation of the skin. This sac is attached to the back of 

 the insect. In it lies the Aphelopus larva, and here it passes the 

 later stages of its development. 



Frequently I have found these sacs break away and fall to the 

 earth ; the homopteron flies on un- 

 concerned, just as it seems to have 

 been by this additional load. Giard 

 states that the host may die. More 

 often this sac remains attached to the 

 host until the Proctotrupid larva es- 

 capes, and falls either to the ground 

 or on to the branches. It then pupates 

 in a coarse case very similar to that 

 formed by the Braconida. TheAphelopus 

 larva is long, and has a transverse row 

 of long stiff bristles on each segment. 



The effect of these hymenopterous 

 parasites is very marked. Giard refers 

 to them as causing parasitic castration 

 (Castration parasitaire). They reduce 

 the size of the external genitals, fre- 

 quently to such an extent that only 

 vestiges remain, and at the same time 

 alter their form. 



The other important group of parasites are the larva; of the 

 dipterous family of Pipunculidw. 



Several larva were found in Chloritcc sent from Kent belonging to 

 a species of Atelenura. In France the species found by Giard working 

 with the Proctotrupids appears to be Atelenura, spuria, Meigen. The 

 effect of these larva is also to produce parasitic castration. I do 

 not know if any changes take place in the female hoppers.* The 

 Atelenura larva lives within the body of the Typhlocybidse. The 

 parasitised abdomen swells to such an extent that it passes well 

 beyond the wings, so that an invaded specimen can at once be told. 

 * Giard distinctly states so. 



IF. Edenden. 



FIG. 264. YELLOW LEAF HOPPER 

 ATTACKED BY A PKOCTOTRUPIP, 



A, tltylacia. 



