Directions for Collecting and Preserving Insects Part 6

The necessity of rearing to obtain perfect specimens is even more important in the case of the Microlepidoptera than with the larger forms, and many species are very easily reared and can thus be obtained in quant.i.ty. The Micros are abundant from early spring to late fall about shrubbery, in open fields, and along the edges of woods. They are, for the most part, day fliers, being on the wing chiefly in the latter part of the day and early evening. As soon as collected they should be transferred to pill-boxes and the greatest care should be exercised to avoid mutilating them, as the slightest touch will denude them of a portion of their scales or break their limbs or antennae. Lord Walsingham thus gives his experience in collecting Micros:

I go out with a coat provided with large pockets inside and out, containing an a.s.sortment of pill-boxes, generally of three sizes, gla.s.s-bottomed pill-boxes preferred, a bag slung over my shoulder, and a net. Unless searching for particular day-flying species, I prefer the last three hours before dark. As the sun goes down many species move which do not stir at other times. I watch the tops of the gra.s.s, the stems of the flowers, the twigs of the trees; I disturb leaves and low-growing plants with a short switch and secure each little moth that moves, taking each out of the net in a separate pill-box, selected according to the size of the insect, as he runs up the net to escape.

Transferring the full boxes to the bag I continue the process until moths cease flying or night sets in. Many species can be taken with a lamp after dark.

_Collecting the early States._--The careful entomologist who prides himself on the appearance of his specimens, will, as stated above, rely largely on collecting the early states and on rearing the insects, for his material. The Macrolepidoptera have either a single or two broods, or more, in a season, and the collection of the early states will be greatly facilitated if a knowledge of the insect's life-habits is first obtained. The eggs are often found on the food plants of the species, and where they are deposited in ma.s.ses they afford a very easy method of getting the larvae in numbers. In many cases, however, the eggs are deposited singly and their discovery then becomes a difficult matter.

More satisfactory in some respects is the method of obtaining the eggs from captured gravid females, and the general collector should always be on the lookout for females of rare species from which he may be able to obtain eggs. A single battered female may, in this way, be the source of large numbers of excellent reared specimens. Many rare Lepidopterous larvae may be obtained by the use of the beating net and by beating foliage over an umbrella. A very satisfactory method consists in collecting pupae, which may frequently be found in numbers about the bases of the trees on which the larvae feed. Many larvae of the large family of Owlet Moths (_Noctuidae_) are found either on the surface of the ground or under various substances, while others burrow into the stems of the different herbaceous plants, some being subaquatic and feeding on the underside of leaves or in the stems of aquatic plants. In the case of Microlepidoptera, their habit as larvae, of mining leaves or tying or webbing them together, affords an easy means of detecting their presence in most cases. The miners are easily noticed by the discolored spots on the leaves or the wavy, pale, or brown lines marking their burrows. The presence of others is indicated by the leaves being drawn together and united with webs, or withered and brown from being skeletonized by the larvae. Many species are case-bearers, and live upon the leaves and branches of trees and plants, dragging their cases along with them. Others burrow in gra.s.ses or in the stems of plants or the trunks of trees, or in fungi. In the case of the leaf-miners and leaf-tiers, little difficulty is experienced in rearing the imagoes.

The care of the larvae, the outfit required, and the methods of breeding will be described in later sections.

COLLECTING HEMIPTERA.

[Ill.u.s.tration: FIG. 74.--A Pentatomid (_Stiretrus anchoraga_).]

[Ill.u.s.tration: FIG. 75.--The Blood-sucking Cone-nose (_Conorhinus sanguisuga_). _a_, mature bug; _b_, pupa.]

For the most part the directions for collecting Coleoptera will apply to this order of insects equally well, especially so far as concerns the first section of the order (Heteroptera), and the higher families of the second section (h.o.m.optera). A few directions may be given for the lower forms, including the Aphididae, Coccidae, Aleurodidae, and Psyllidae, and the suborder Parasita, including the degraded forms which infest man and the lower animals. The Plant-lice or Aphides should always be collected in connection with their food-plants, and it is very essential also to collect the same species at different seasons of the year to obtain the different forms or generations, which frequently present very marked differences. It is also very necessary to secure the winged forms, which are usually produced toward autumn, and without which the species are not easily identified. The Bark lice or Scale-insects should also be collected in connection with the leaves or twigs which they infest. The males of these insects are minute and, as a rule, two-winged, resembling small gnats, and may be bred from the male scales. The females are for the most part stationary, being fixed to the plant by the protecting, waxy, excretion or scale. The Flea-lice (_Psyllidae_) frequently produce galls, and these should always be collected with the insect architects.

Some species do not produce galls, and may be collected by sweeping. The Hackberry is infested by large numbers of species of Psyllids, and these produce a great variety of interesting galls. The Aleurodidae (Fringe-scales) are delicate insects, and easily injured in the taking; they are therefore best reared from their stationary and fringed larvae and pupae, which occur on the leaves of many plants. Leaves bearing the latter should also be collected and pinned or preserved in alcohol. The Parasita, the lowest representatives of the order, may be obtained from the domestic and wild animals which they infest.

[Ill.u.s.tration: FIG. 76.--The Bed-bug (_Acanthia lectularia_). _a_, young; _b_, adult--enlarged.]

[Ill.u.s.tration: FIG. 77.--The Short-nosed Ox-louse (_Haematopinus eurysternus_). _a_, female; _b_, rostrum; _c_, ventral surface, last segments of male; _d_, female; _e_, egg; _f_, surface of egg greatly enlarged.]

COLLECTING DIPTERA.

[Ill.u.s.tration: FIG. 78.--Ox Bot-fly (_Hypoderma bovis_) enlarged. (After Brauer.)]

[Ill.u.s.tration: FIG. 79.--The Collecting Shears. (After Kiesenwetter.)]

[Ill.u.s.tration: FIG. 80.--A Bee-fly (_Anthrax hypomelas_). _a_, larva from side; _b_, pupal skin protruding from cutworm chrysalis; _c_, pupa; _d_, imago--all enlarged.]

Most Diptera frequent flowers and may be collected with a sweeping net without much difficulty. The best season is from April to June, and the bloom of the Willow, Alder, Plum, Cherry, Dogwood, Blackberry, etc., will ordinarily yield a bountiful supply of specimens and species.

Parasitic and saprophytic forms may also readily be obtained by breeding, the former as in the case of the parasitic Hymenoptera, and the latter from decaying vegetable matter and fungi. The Diptera require the most delicate treatment, and the greatest care must be exercised both in collecting and handling. A light sweep net is the best implement for collecting and the contents of the net should frequently be emptied into bottles provided with blotting paper to absorb the excess of moisture. Very small Diptera should not be killed when they can not be immediately pinned, and hairy flies should never be taken from the net with the hand, but should be handled with fine forceps. A pair of special collecting shears has been used by Lord Walsingham very successfully. It is represented in the accompanying figure, and consists of a pair of screen-covered disks, between which the fly is caught. The insect is at once pinned through the screen and may be removed and transferred to a box containing a sponge soaked in chloroform. The use of this implement is especially advisable in the case of the Bee-flies (_Bombiliidae_) and other hairy forms which are liable to be rubbed when collected in the ordinary net. The Gall-making Diptera (_Cecidomyidae_) are of little value unless accompanied with their galls, and the aim should always be to collect the galls and rear the insects rather than the keeping of specimens taken in the course of general collecting with a sweep net. The rearing of Cecidomyidae is, however, a delicate task, and requires considerable experience. Some knowledge of the habits of the species is very essential to success. From immature galls no rearings need be expected. A good plan is to examine the galls from time to time and collect them when it is found that the larvae are beginning to abandon them. In the case of species like the common Cone Gall-gnat of the Willow, the larvae of which do not leave the gall to undergo transformation in the earth, it is advisable not to gather the galls until the transformation to the pupa state takes place, which, in this species, occurs in early spring. The various leaf-mining and seed inhabiting species can be treated as in the case of the Microlepidoptera.

[Ill.u.s.tration: FIG. 81.--A Syrphus-fly.]

COLLECTING ORTHOPTERA.

[Ill.u.s.tration: FIG. 82.--A blind Cricket (_Hadenalcus_) from Mammoth Cave. (From Packard.)]

The insects of this order may all be collected by the use of the sweeping net. Some of the families are attracted to light, as certain of the roaches and green locusts, or Katydids (_Locustidae_). Our common roaches (_Blattidae_) are cosmopolitan insects, and infest dwellings.

Certain species are also found about ponds, under rotten logs, the bark of trees, and particularly in decaying vegetable matter. In the tropics the species are very abundant, but aside from the domestic forms, they occur rarely in northern lat.i.tudes. The collection of the egg-cases (ootheca) is important as they furnish many interesting characters. The Mantidae, of which the Preying Mantis (_Phasmomantis carolina_) is a type, are sluggish, carnivorous insects frequently found about houses and may best be collected by general sweeping of vegetation. The Phasmidae or Walking-sticks are herbivorous and may be collected in the midst of vegetation by sweeping or by the hand. The crickets (_Gryllidae_) frequent, for the most part, moist situations. Certain forms, like the Mole-cricket and the Jumping Water-crickets (_Trydactylus_ spp.), burrow in moist soil and occur in numbers near the edges of ponds and water courses. The katydids and locusts are abundant on low shrubs or trees and in pasture and meadow land, but are most numerous in the somewhat dry, arid regions of the West. Most of these insects mature in late summer and fall and should be collected at this season. The Forficulidae or Earwigs are very odd-looking insects, resembling somewhat the Rove-beetles (_Staphylinidae_), and are provided with a prominent a.n.a.l forceps. They are very rare in the United States, are nocturnal in habit; and, flying about at dusk, may be attracted to light or may be secured by sweeping after nightfall. They feed on flowers and fruit.

COLLECTING NEUROPTERA.

As indicated in the preliminary outline of cla.s.sification, this large order has been divided into many orders by later entomologists. It has also been divided, as indicated, into two grand divisions, the Pseudoneuroptera, comprising those insects with incomplete transformations, and the Neuroptera proper, comprising those insects whose metamorphoses are complete. It will be convenient to discuss these insects under these two heads.

_Pseudoneuroptera._--Spring-tails, Bird-lice, Stone-flies, White-ants, Dragon-flies, May-flies.

[Ill.u.s.tration: FIG. 83.--A Spring-tail (_Degeeria lanuginosa_).]

The Spring-tails, Fish-moths, etc., representing the primitive stock from which the higher forms have developed, have a varied habit and hence are to be found in divers situations. The Spring-tails (_Collembola_, etc.), occur in damp and moist places, usually in immense numbers. The Fish-moths and Book-mites are common household pests, but also occur outdoors under logs, boards, bricks, and rubbish of all sorts. In houses they feed on the starch paste beneath wall-paper and also on the starch in bookbindings and other domestic articles. They may be collected at all seasons and a sieve is the only implement necessary.

[Ill.u.s.tration: FIG. 84.--A Mallophagan (_Trichodectes latus_). (After Denny.)]

The Bird-lice or Mallophaga may be collected at all seasons on birds and mammals. A number of species infest domestic animals, horses, cattle, etc., but the majority of them can be found only by the examination of domestic fowls and wild birds. The Stone-flies (_Perlidae_) are found in the neighborhood of water courses and ponds, are very sluggish in flight, and easily captured with the sweep-net. They are also attracted to light. The Psocidae are a small family of certain degraded wingless forms, comprising the Book-lice, which, as the name implies, infest books, feeding on the starch of the binding. Others have ample wings and closely resemble large Aphides. They occur on the trunks of trees and on foliage, and feed on lichens and other dried vegetable matter. They are gregarious in habit and frequently occur in immense numbers together. In the case of the Termitidae or White-ants, their abundance renders their collection an easy matter. Effort, however, should be made to discover the different forms, the females and soldiers as well as the workers.

The former may be found in rotten tree trunks, but are very rarely met with. In the tropics many species occur and construct curious nests, either attaching them to the boughs of trees or building them in the form of pyramids on the ground. The Dragon-flies (_Libellulidae_,) are collected in the same way as the Diurnal Lepidoptera. They are very swift flyers, and are practically always on the wing. Their collection requires some degree of skill in the use of the net. A good method consists in visiting, in the early morning, water courses in which the larval and pupal states are pa.s.sed, and capturing the adults just as they issue from their pupal skins at the edges of the pond or stream. In cold weather they are less active and may frequently be found clinging to trees and plants, particularly in the vicinity of their breeding places. May-flies (_Ephemeridae_) occur in immense numbers near their breeding places in ponds and streams and are also attracted in large quant.i.ties to electric lights. Their collection is therefore an easy matter, but on account of the very fragile nature of these insects the utmost care must be employed in handling them. The early states of all the aquatic forms mentioned above may be obtained for breeding by the use of the dip net by dragging it forcibly against water plants.

[Ill.u.s.tration: FIG. 85.--_b_, a May-fly (_Palingenia bilineata_); _c_, its larva; _a_, a Caddis-fly (_Macronema zebratum_).]

[Ill.u.s.tration: FIG. 86.--A Dragon-fly (_Libellula_). (From Packard.)]

[Ill.u.s.tration: FIG. 87.--A Dragon-fly (_Agrion_). (From Packard.)]

_Neuroptera proper_ (h.e.l.lgrammites, Lace-wings, Ant-lions, Caddis-flies, etc.)--Among the largest insects of this order are the Sialidae, which includes the enormous h.e.l.lgrammite Fly, _Corydalus cornutus_. The larvae 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 larvae, 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 larvae, 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 larvae 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.

[Ill.u.s.tration: FIG. 88.--An Ant-lion, adult (_Myrmeleon_). (From Packard.)]

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.--Larvae, pupae, 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 quant.i.ty 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. Larvae of Lepidoptera and Tenthredinidae should be placed in a box with a quant.i.ty of the leaves of the plant on which they were found. Larvae, 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. Larvae found in roots or stems of living plants can generally be reared to maturity only if the whole plant with a quant.i.ty of the surrounding soil is taken home, and for this purpose the large collecting box, just mentioned, is very useful. Most Coleopterous or other larvae found under bark or in solid wood can be reared only if large sections of the wood are obtained and the larvae 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 larvae, and care should be taken with such not to inclose two or more specimens in one box. Most larvae 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 larvae 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 larvae 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 ma.s.s of debris 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 larvae 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 s.p.a.ce 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 subst.i.tutes where no pure alcohol can be obtained, but are not especially to be recommended.

_Chloroform and Ether._--Killing with the fumes of _chloroform_ or _ether_ (sulphuric or acetic) or _benzine_, or some other etheric oil, is often practiced and advocated by those who, for any reason, dislike the use of alcohol or object, on account of its poisonous nature, to the use of cyanide of pota.s.sium, and they are of especial value in the case of b.u.t.terflies and moths, Hymenoptera and Diptera. "A small and stout bottle of chloroform or ether, with a brush securely inserted into the cork (Fig. 89), will be found very serviceable. A slight moistening through the air net will stupefy most insects caught in it, and facilitate their removal to the cyanide bottle; while a touch or two with the wet brush under the head and thorax, will kill the more delicate specimens outright, without in the least injuring them. Another way of using chloroform is by means of a small, hollow tube pa.s.sed through the cork, what is called jeweler's hollow wire answering the purpose. The liquid evaporates more readily in such a bottle, and I altogether prefer the first mentioned. Some large insects, and especially female moths, whose size prevents the use of the ordinary cyanide bottles, are difficult to kill. With these, fluttering may be prevented by the use of chloroform, or they may be killed by puncturing the thorax or piercing the body longitudinally, with a needle dipped in liquid cyanide, or oxalic acid. A long bottle with a needle thrust into the cork may be kept for this purpose; but the needle must be of ivory or bone, as those of metal are corroded and eaten by the liquids. * * *

[Ill.u.s.tration: FIG. 89.--Chloroform bottle with brush.]

"For killing small and delicate moths which have been bred, I find nothing more handy than chloroform. They may be caught in turned wooden boxes which are kept by every druggist; and a touch of the chloroform on the outside of the box immediately stupefies them. It has a tendency to stiffen them, however, and they are best set immediately after death."

[Ill.u.s.tration: FIG. 90.--Bottle with liquid cyanide.]