[Neuroptera proper] (Hellgrammites, Lace-wings, Ant-lions, Caddis-flies, etc.)—Among the largest insects of this order are the Sialidæ, which includes the enormous Hellgrammite Fly, Corydalus cornutus. The larvæ of this insect are carnivorous and occur in streams, under stones, etc. The adults may be collected in neighboring situations and are also attracted to light. The Lace-wing flies (Chrysopa), Ant-lions, etc., are carnivorous as larvæ, and occur, the former among the Aphides which infest various plants and the latter at the bottom of pits in loose, sandy soil. The adults may be obtained by general sweeping and are also attracted to light. The most interesting insects of this order are the Caddis-flies, on account of the peculiar and frequently very beautiful cases constructed by their larvæ, which it is important to collect. The Caddis-flies breed in ponds and lakes and the adults may be collected in such situations or at light. The larvæ may easily be reared, and should be collected for this purpose. Most of the insects named in this order are extremely delicate and require great care in handling.
KILLING AND PRESERVING INSECTS.
Between the collecting of the specimens and their final disposition in a well-arranged cabinet, a good deal of mechanical work is necessary, involving a skill and dexterity which can be thoroughly acquired only by practice.
[First Preservation of living Specimens.]—Larvæ, pupæ, or imagoes, intended for rearing purposes, must be kept alive, and are best placed, after capture, in tin boxes of various sizes, according to the number of specimens to be put in each and according to the size or nature of the food plant, etc., on or in which the specimens are found, and of which a quantity must always be taken home. For larger tin boxes those known as “Seidlitz powder boxes,” described and figured below, which can be made to order at any tinner's shop, are well adapted, and smaller tin boxes of a convenient round form can be obtained of the watchmaker. The collector will find it advisable to take with him on his longer jaunts a larger tin collecting box as well as the smaller boxes, and for this purpose nothing is better than a good botanist's collecting can or vasculum. All tin boxes used for entomological purposes should be tight, and the cover should so fit that it neither drops off too readily nor closes too tightly. Larvæ of Lepidoptera and Tenthredinidæ should be placed in a box with a quantity of the leaves of the plant on which they were found. Larvæ, especially of Coleoptera, found in the earth or in decayed wood, should be placed in a box filled with such earth or wood, so as to prevent shaking or rattling about. Larvæ found in roots or stems of living plants can generally be reared to maturity only if the whole plant with a quantity of the surrounding soil is taken home, and for this purpose the large collecting box, just mentioned, is very useful. Most Coleopterous or other larvæ found under bark or in solid wood can be reared only if large sections of the wood are obtained and the larvæ are full grown or nearly so. This holds true, also, of species breeding in seeds and with most leaf-mining species. The greatest difficulty is experienced with carnivorous Coleopterous larvæ, and care should be taken with such not to inclose two or more specimens in one box. Most larvæ die quickly if placed in an empty box, and this is especially true of predaceous species; so that it is always advisable to pack the box with moist soil, decaying wood, leaves or other similar substance. Aquatic larvæ should be carried in tin boxes filled with wet moss or some water plant, for, if placed in corked vials with water, they die quickly.
[Killing Specimens.]—Specimens not intended for rearing should be killed immediately after capture unless for each specimen a separate vial or box can be provided. If a number of miscellaneous insects are put in the same vial the stronger specimens will, in a short time, crush or otherwise injure the more delicate ones or the predaceous species will devour any others they can master. But even where the specimens are killed immediately the following rule should be observed: Do not put large and small specimens in the same vial, but provide a larger bottle for the larger specimens, and one, or still better, several, smaller vials for the medium-sized and very small specimens. The importance of this rule is recognized by all experienced collectors.
There are several methods of killing insects, each having its own peculiar advantages and drawbacks.
[Alcohol.]—The use of alcohol will, on the whole, prove the most satisfactory method of killing Coleoptera, many Hemiptera, some Neuroptera, and larvæ of all sorts. Only the best quality of alcohol should be used, but it should be diluted with from 30 to 40 per cent of pure water, the greatest care being taken to keep the alcohol as clean as possible. During the collecting a mass of débris and dirt is apt to be thrown into the bottle, and when this is the case the alcohol should be changed even during short excursions. At any rate, upon the return from the excursion, the specimens should be at once taken from the bottle and washed in pure alcohol in a shallow vessel. The larvæ and other material intended for permanent preservation in alcohol should be transferred to suitable vials and the material to be mounted cleansed with chloroform or acetic ether and then prepared for the cabinet. If it is inconvenient or impossible to mount the Coleoptera, etc., soon after the return from the excursion they should be washed, dried, and placed in pill boxes between layers of soft paper, or they may be replaced in a vial with pure alcohol. On longer collecting trips, lasting several days or weeks, specimens will keep thus very well, provided they are not shaken up, and this can be prevented by filling the empty space in the vial with cotton or soft paper. If the bottle is a large one and contains many large specimens the alcohol should be renewed three or four times at intervals of eight or ten days; otherwise the specimens are liable to decompose. Small and delicate specimens, if they are to be kept in alcohol, should be treated with still greater care. Upon the return from the excursion they should also be cleaned in pure alcohol and placed in small vials into which a very few drops of alcohol, just sufficient to keep the contents moist, are poured. The vial should be corked as tightly as possible and the specimens will keep pretty well for an indefinite time.
The drawbacks to the use of alcohol are: 1st, that all hairy specimens are liable to spoil; 2ndly, that all Coleoptera with soft integuments spread the wing-cases apart if kept too long in it. The advantage of the alcohol is that it is the simplest and least troublesome fluid for naturalists traveling in distant countries who are not specialists in entomology. Specimens killed in alcohol are also less liable to be attacked by verdigris when pinned than those killed by some other method. Rum, whisky, or similar strong alcoholic liquors may be used as substitutes where no pure alcohol can be obtained, but are not especially to be recommended.
