RHYNCHOTA. 



199 



SPKUCE-gall APHID (Chermes abietis). 

 Larva ; b, An older larva with its moulded skin still 

 attached to it ; c, Winged insect ; d, The gall. (All 

 enlarged. ) 



provided with one pair of wings ; the hind-wings being rudimentary or altogether 

 absent ; they have rather long antennas, distinct eyes, and, in some cases, are 

 furnished with two long bristle -like a 



tails. These winged males are very 

 rarely seen, which is accounted for by 

 the fact that their mouth -parts are 

 atrophied, so that they are incapable of 

 taking nourishment, and live only a 

 short time. The females are always 

 wingless, and usually remain fixed to 

 one spot, with their beak buried in the 

 tissues of the plant, and their back 

 often spread out in the form of a shield 

 covering the head and body. The beak 

 is generally three-jointed, the antennas 

 are short, and in the tarsi, which appear 

 at first sight to consist of but one joint, 

 two or three joints may on close examination be distinguished, the last ending, as 

 a rule, in a single claw. In many species the female dies shortly after laying eggs 

 beneath her when her body dries up and remains as a protective cover for them. 

 When the larvae are hatched they soon leave this shelter, and rove about the food 

 plant in search of a suitable place in which to insert their beaks and begin the 

 operation of pumping up the sap. They cast their skin several times in the course 

 of their growth ; and those which become adult females undergo no great change 

 in appearance, beyond an increase in their size, a gradual lengthening of the 



antennas, and a partial or almost complete obliter- 

 ation of the segmentation of their bodies. With 

 the male larvae the case is different ; these, unlike 

 all others belonging to the order, undergoing a true 

 metamorphosis before reaching the perfect state. 

 Each prepares for itself a sort of cocoon, and 

 it becomes transformed into a quiescent pupa, 

 from which, after a certain lapse of time, the 

 winged insect emerges. In Ovthezia and other 

 genera the female, instead of keeping to one spot 

 on the food-plant, moves about and taps it at 

 different points in order to extract the sap. 

 When the eggs are laid, she envelops them in 

 a kind of white cottony secretion and leaves 

 them. Some species penetrate beneath the 

 epidermis of their food-plant, and often cause 

 the formation of galls, which, growing up around 

 them, sometimes take the most extraordinary 

 shapes. Scale-insects are probably more numerous within the tropics than in more 

 temperate regions, although comparatively few of these tropical species have been 

 described. These insects are found on the bark and leaves, and sometimes 



female of Orthezict icrtica (nat. size). 



