Fig. 58.—A Larva Glass.
If you find it necessary to move the larvæ yourself from the stale food, never touch them with your fingers, but lift them gently by means of a small camel-hair brush. Larger larvæ need never be moved at all. They will always search out fresh food for themselves, and the stale may be removed after they have quitted it.
For rearing larger species ordinary bottles are hardly satisfactory, and we must either use large jars or construct cages of some kind.
An ordinary bell jar such as is used for covering ferns or for aquaria makes a very useful 'larva glass.' Place a small bottle of water at the bottom, and then introduce sufficient dry clean sand or sifted soil to reach up to its neck. On the top of this place a layer of moss or cocoa-nut fibre. Next introduce the food plant, fixing it firmly in the bottle of water, and plugging up the space between
the stem and the rim with cotton wool. This precaution is to prevent the larvæ from falling into the water as they attempt to pass up or down the stem, and the wool also helps to keep the twig in a vertical position. The glass is now ready for the caterpillars, but it is advisable to keep a covering of muslin or gauze over the top in all cases even though the larvæ contained are unable to creep up the surface of glass, for the great enemies of caterpillars—the ichneumon flies—are always on the alert, and will often take advantage of an open window to 'sting' the larva rearer's pets.
Another form of larva glass can easily be made out of a large glass jar if you know how to cut off the bottom, or of a chemist's bell jar which is open both at top and bottom. In this case the bottle of water and the soil are arranged as before in a pan of unglazed earthenware, and then covered over with the glass. This is shown in [fig. 58], and is an exceedingly convenient larva house, since the lifting of the glass enables you to get at the insects without any trouble.
