74 INSECT ARTIZANS AND THEIR WORK 



the other way about, and they have to partially 

 block up a crevice that would be otherwise incon- 

 veniently roomy. Whatever the Mason's length 

 may be, its breadth is very little, and it contrives 

 the burrow to have only sufficient " elbow-room." 

 There are many inquisitive birds about with a 

 taste for fat little grubs, and the smaller the entrance 

 holes to nests the safer for the defenceless grub. 

 Ichneumon flies with long, slender ovipositors, 

 and other parasitical insects of their own order, 

 have to be guarded against so far as possible ; but 

 the latter are the more subtle, and often succeed 

 in introducing their own eggs to the utter ruin of 

 the Mason Wasp's plans. If the parasite does not 

 begin by eating up its host, it devours all the pro- 

 visions and allows the host to perish by starvation. 



One species, Odynerus reniformis, described by 

 Fabre, hangs its egg from the roof of the cell by a 

 silk thread, a provision to protect the newly hatched 

 grub from being crushed by movements of the 

 score or so of small caterpillars that are placed 

 inside after the egg is laid. From the egg-shell the 

 young grub can reach down to its first caterpillar, 

 and, about twenty-four hours later, when this 'is 

 devoured, the grub is believed to cast its skin and 

 to be sufficiently strong to take care of itself among 

 the only partially stupefied caterpillars. It eats 

 them in the order in which they were brought in. 



Let readers who share the common enmity to 

 wasps of all sorts bear in mind these facts about 

 their utilization of caterpillars. Let such consider 



