PLATE XCIX. 



Lachnus viMiNALis. (Page 53.) 



Fig. 1. — Apterous viviparous female. 



Fig. 2. — Pupa of the same. 



Fig. 3. — Imago. The tubercle seen between the 

 cornicles in the previous forms is here wanting. 



Fig. 4. — Imago, showing the wings folded horizon- 

 tally whilst at rest. This position, however, is not 

 always assumed by the wings. 



Fig. 5. — A portion of willow bark infested by the 

 above Aphis. Alarm is shown by the jerking upwards 

 of the hind legs of the insects. 



Fig. 6. — Dorsal papilla. The apex shows the ori- 

 fices of minute vessels, which probably secrete some 

 liquid, disgusting to the parasites which hover over the 

 infested branches. The winged insects, by their 

 activity, are less open to the attacks of Syrphus, 

 Coryna, &c., and therefore they are not provided with 

 this gland (?). 



