3 88 



ANIMAL LIFE-HISTORIES 



positing each of them in the lowest internode of a distinct plant. 

 This takes place in early summer, and the larva spends the rest 

 of this season in gradually working its way up the stem, biting 



through the knots as they are encoun- 

 tered. It then travels down again, and 

 is fully grown by the time it gets near 

 the ground. Now follows the most 

 remarkable event, for the larva partly 

 bites through the stem all the way 

 round, about an inch from its base, the 

 object unconsciously obtained being that 

 later on it may be easily broken off by 

 the wind, thus leaving a free means of 

 exit for the fully-formed insect. This 

 accomplished, the larva descends to the 

 neighbourhood of the root and weaves 

 a transparent silken cocoon, in which it 

 remains dormant till the following May, 

 when it becomes a pupa, the perfect 

 insect making its appearance soon after- 

 wards. 



The numerous species belonging to 

 the Saw-Flies Proper (Tenthredinidce) are familiar pests, in which 

 the female possesses an ovipositor constructed on much the same 

 principle as that of the Wood- Wasp (see p. 387), but the two 

 saws are elaborate curved plates, with teeth on their edges and 



sharp ridges on the outer side (fig. 911), 

 the latter having a rasping function. 

 When in use they are used alternately, 

 sliding on their supporting pieces. Sharp 

 remarks on these insects as follows (in 

 The Cambridge Natural History)'. 



Fig. 9I ,_ Side-view of Ovipositor of " In the CaSe f SOme SpedeS the 

 Rose Saw-Fly (Hylotoma rosa}, much en- niOn SaW-Fly (HvlotOIHa rOSCZ) of 

 larged. I. AP., intestinal aperture. i 



rose-bushes, for instance, there is no 



difficulty in observing the operation; indeed, old Reaumur, when 

 speaking of the placid disposition of the Saw-Flies, suggests that 

 it was given them so that we may easily observe their charming 

 operations. We cannot but regret that in these days we are un- 

 able to take so complacent a view of the arrangements of nature. 



Fig. 910. Corn Saw 



i, Adult female (2 indicates actual size); 

 3, larva within a haulm of rye; 4 and 5, the 

 same, natural size and enlarged; 6, an Ich- 

 neumon-Fly which lays its eggs within the 

 Saw-Fly larvae (7 indicates actual size). 



