THE HYLOTOMA. 171 
twig or stem, which it likes, and immediately the insect clasps 
it with its legs, bends the back, and places its head low. Then 
the saw suddenly appears under the end of the body, and is dug 
deeply into the green stem like a knife. Immediately the skin 
of the twig is pierced, the lamina which form the: double saw 
are stretched slightly apart, and the gentle saw-like motion cuts 
deeper and deeper. Each saw cuts so as to separate from its 
fellow, and to widen the slit, whilst the rough parts of the 
outside of the saws scrape and enlarge the wound also. In a 
few seconds or minutes the slit has become large enough for the 
purpose of the saw-fly, and when this time has arrived the insect 
rests perfectly still for a short period, and the saws separate 
sideways and enlarge the slit; at the same time an egg passes 
down between them slowly but surely. The egg is laid at the 
bottom of the slit in safety, but more has to be done to ensure 
the future comfort of the larva and its freedom from danger. If 
the egg were simply left at the bottom of the wound the vegetable 
fibrous cells would soon close over and effectually imprison it 
for ever, and the young larva would be crushed before it was born, 
or starved. Every care is taken, however, to prevent this mis- 
fortune. The egg is hardly laid before a mucus secretion, provided 
by special glandular structures, escapes from the insect, and enters 
the wound and covers its sides; it acts as an irritant to the 
plant, and soon makes itself felt by the vegetable tissues, which 
it alters and indurates in a remarkable manner. No sooner is 
it deposited than the fibres become wider apart, and soon blacken, 
whilst the deeper-seated tissues become thickened and impaired, 
so far as their growing powers are concerned. The egg thus 
remains free at the bottom of the slit, and does not suffer from 
the growth of the surrounding tissues, thanks to the glandular 
secretion. 
Ege after egg is deposited in the same manner, and with the 
same precautions, and we may often distinguish the twigs where 
all this has gone on, and which contain a long series of eggs in 
separate slits. Sometimes only three or four wounds may be 
counted, but ten or fifteen or more punctures are often made. 
The operation of laying is by no means easy, and it requires 
much care; so the female only deposits a few eggs every day, 
