The earliest records belong to ancient China. In 1235 Sung Tz’u, a Chinese “death investigator,” wrote a book entitled The Washing Away of Wrongs (translated by McKnight, 1981) in which what was known in forensic science at that time was detailed. In this text, an actual forensic entomology case was recounted, with the best known historic case being given. A murder had been committed in a little village in China. A man had been hacked to death with a rice-harvesting sickle. Because the village was one where rice was grown, everyone possessed a sickle, which meant that there were therefore many suspects. A professor at UC Davis, Robert Kimsey, explains how the murderer was caught; “The local magistrate very cleverly lined up every one of the farmers with their sickles out in the field. He walked up and down the line and pointed to the man who had committed the murder. The evidence he used to identify this man as a murderer-who later confessed, by the way-was the fact that green bottle flies were attracted to this man’s sickle. And nobody else, of course, had green bottle flies on their sickle because the flies were only attracted to a surface that had blood on it. No matter how rigorously you cleaned your sickle, you would still have remnants which these flies would be able to detect.”

Since those times, forensic entomology has made great progress. The way insect evidence helps justice works through the successive colonization of a corpse by a predictable succession of arthropod species. Different types of insects start coming right after death occurs. Organic remains, like flesh, blood, waste material, bone marrow, and hairs all attract certain types of insects. Owing to the time difference between the decaying body parts, the flies arrive at different times. They consume the parts that are nutritious for them and leave the body for another group.

As a manifestation of the divine name Quddus (the All-Holy), dead bodies decompose and nature is kept clean. Thus, the process started by microorganisms is made faster by the insects. Blow flies are among the first group of workers in this respect, whereas the dermestids, for instance, do their duty in the later stages of decomposition. The larvae of dermestids are not found before the body dry outs. The larvae and adults feed on dry skin and hair, as well as other dry dead organic animal matter. Dermestids are a common pest in homes, as well as being undesirable in insect collections and taxidermists collections at museums.

The first month after death is the most effective time for the application of forensic entomology. When death takes place, the insects start to arrive within minutes. However, it should be noted that insect evidence does not always tell us about the exact time of death. But at least we can infer that death occurred at a time that is greater than the age of the larvae that are developed in the body. If we have sound knowledge about the life cycles of the relevant insects, we can make more accurate predictions.

Another thing entomology helps us find out is the location of a murder. Sometimes a victim is moved after a murder in order to get rid of important evidence. For instance, a victim can be taken to a mountainous area after being killed in a town at low altitude. Entomologists can tell you about the habitat of the insects found on the body and give one a good idea about where the murder took place. Many insects live in very special geographical conditions. The altitude, temperature, and vegetation all affect the types of insects that live in the area. Furthermore, a meticulous entomological study will tell you whether the body has been, moved, the season in which it was killed, and whether the murder was committed indoors or outdoors.

Entomologists even help forensic experts with the cause of death. Particularly when the body has already decayed, it can be difficult for the police to determine the cause of death. In normal conditions, insects lay their eggs in certain parts of a body. If there are open wounds however, they will also lay their eggs there. So, if any eggs are found in unusual spots they indicate a probable wound.

When a murder or suicide is suspected to have resulted due to poisoning and if the body is decomposed, toxicological analyses that are made on the insects or the larvae taken from the body can help.

Bergeret (1855), who resided near Paris was the first westerner to use insects as forensic indicators. The body of a baby was found behind the plaster mantle in a house, and an investigation was begun. Bergeret determined that the assemblage of insects associated with the corpse pointed to a state of decay that dated back several years; consequently, the question of guilt was thrown upon the earlier occupants of the house, and not upon the current ones.

Case histories have documented the utility of medicocriminal entomology and point out the unique contributions that this field of science has made. Nuorteva et al. (1967, 1974) presented a series of cases from Finland in which blow flies were used as indicators for indoor as well as outdoor death scenes, and where the immature (larval) or adult stages were used for identification. Leclercq (1969) provided a typical case scenario and outlined how insect data were used to corroborate information obtained from other sources. Bernard Greenberg (1985) outlined several cases, including a description of how laboratory fly-rearing data were used to calculate the number of accumulated degree hours (ADH) required for certain blow fly species to develop, and how such data were applied to the solution of a murder case in Illinois. In another recent case, Greenberg described how the absence of insects in a seemingly straightforward death scene led to a killer’s confession. A window next to the victim had been open when the body was found, thus giving the impression that the murderer had forced entry into the room the night before. However, the air conditioned room was cool, even though it was very hot outdoors. In reality, the killer was known to the victim, had a key, and had returned to “set the stage,” opening the window just prior to feigning discovery of the corpse. The insects thus had insufficient time to colonize the body as the window had been closed prior to the return of the killer. When confronted by this biological reality as pointed out by medicocriminal entomology, the killer confessed.

A Hungarian ferry skipper had been condemned to life imprisonment for the murder of a postmaster, whose stabbed body had been found one evening in September on the ferry. The ferry skipper had arrived at 18:00 that day, and the body of the murdered postmaster had been found some hours later. The autopsy was performed the next day at 16:00. Masses of yellowish fly eggs and numerous newly hatched larvae of 1 to 2 mm in length were present, and the findings were recorded in the autopsy report. No attention was paid to this observation at the trial, however. On assumed evidence, the ferry skipper was condemned to life imprisonment in spite of his swearing that he was innocent. Eight years later the case was reopened. At the new trial, Dr. Mihalyi pointed out that no sarcophagous flies are active in Hungary after 18:00 in the month of September. He also recalled some of his experiments indicating that, at a temperature of 26 degrees Celsius, the yellowish eggs of Lucilia caesar (L.) hatch after 13 hours, those of L. sericata (Meigen) hatch after 10-11 hours, and those of Phormia terranovae Robineau-Desvoidy 14-16 hours after oviposition. These data, when applied to the case of the ferry skipper, led to the conclusion that it was not possible for the eggs to have hatched if they had been laid during the day the autopsy was performed, and that they must have been laid during the previous day before 18:00, since the flies are not active after this time. Dr. Mihalyi’s data on oviposition was verified and, on the basis of this and other evidence, the ferry skipper was released from prison.

Entomology, along with other sciences whisper in our ear that in “the Book of the Universe” there are different signs that lead us to the truth; they are there for us to use if we search for them and fulfill the requirement of causes. This is when the world will open its mysteries to us.

Reference

• http://www.ucdmag.ucdavis.edu/su99/Feature_Bugs.html
• http://www.research.missouri.edu/entomology/chapter1.html#history
• http://folk.uio.no/mostarke/forens_ent/casehistories/ferry_skipper.html
• The illustration is taken from the poster of the annual Insect Fear Film Festival at the University of Illinois, Feb. 2005.

The spider’s web is woven from a special silk. This is a fibrous protein first secreted as a fluid and then stretched into strands which, because of their strength and elasticity, are extraordinarily resistant to breakage.

Garden spiders (Arena diedemata) make their webs from two different silks. The threads of the main structure are woven from a strong silk which can be stretched further (by as much as 20%) but then loses its strength. By contrast, the other kind of silk, used between the main threads, is lighter and stickier and can be expanded three times without losing its original characteristics. Under a microscope drops containing a reserve of silk can be seen at intervals on these thinner ‘hunting silks’.

After its web is complete the spider hides out of sight, somewhere on the outer strands of the web. When an insect flies into the web and struggles, the spider is alerted by the vibrations and runs out. It rapidly contains the victim’s struggle to escape by tying it up with the silk set aside for this purpose in the drops: the elasticity of the hunting silks is vital in this task. While tying it up, the spider injects the victim with the poison from behind its jaws which both paralyses the insect and acts as a digestive juice softening up the now helpless corpse. The spider then goes on injecting and sucking back fluids until the soft parts of the corpse have been digested – any skeletal parts left over are simply discarded.

Spiders put their weaving skills to a number of different uses. As well as making the insect traps we call spider webs, they weave draglines’ that help them to locate themselves and to break their fall if they should slip. Small spiders spin a sort of ‘parachute’ thread that allows them to be carried on the wind.

Some species of spider make active traps. Menneus spins an elastic net between its legs and sweeps it through the air to catch passing insects. Cledomelea dangles from one leg a blob of sticky silk at the end of a long thread and swings it out to attach its prey. Trapdoor spiders (Ctenizidae) dig a burrow closed by a silken door; when an insect ventures near, the spider darts out to capture the imprudent victim.

Spider webs are beautiful, intricate constructions: threads which serve as scaffolding during the construction process are removed once the web, a mesh of sticky and non-sticky lines, has been completed. The skill of producing webs is clearly instinctive, but the irregularity and variety of web forms shows that the skill is adapted by individual species to serve different functions and suit different circumstances – some webs hang in the air to catch insects as they fly, others are laid across the ground, both at angles calculated (presumably by experience) to lure and intercept prey.

Recent research has shown that some A. Glomosus spiders use ultraviolet rays to attract their prey. In one experiment fruit flies (Drosophila) were set free between two webs lit up by a white beam. One web was that of a A. Glomosus spider and radiated ultraviolet rays; the other was not: the flies were attracted to the former

Another remarkable species are the Dolmedes spiders which have long legs (8-10 cm) and striped, brown bodies. They live near water ponds where they have learnt, despite having very poor sight, to catch fish. Their hunting-gathering technique is of awe-inspiring dexterity and patience, rivaling that of any human fisherman. First the spider walks around on the bank to pick a site suitable for laying a web. Once that is done, it waits patiently, standing partly on water and partly on land. A special sticky secretion helps secure its hold on the surface of the water. While waiting, it prepares its poison in its mouth. When a small fish happens by, the spider plunges forward to seize it, releasing its poison into the water as it does so. As the poison begins to work, the spider turns over making its own body a sort of float for the struggling fish, carries it to land and there consumes it.

Some species of spiders do not make webs to ensnare their prey. Instead, they actively pursue their prey or lie in ambush for it. They are endowed with specially keen sight or touch sense, used respectively for hunting in daylight or in the dark. The ambushing varieties are remarkably well camouflaged – the colour and shape of their bodies making them almost invisible against the immediate background of leaves or bark or stones and sand.

One of the night-hunting spiders of the Amazon jungle spends the day hiding in crevices or in holes in trees, emerging into the jungle at night to stalk its food. Its legs spread the width of a human hand and move with utmost stealth until, when near enough, the spider makes a sudden, final dash, seizing small mammals (humming-birds, for example), stunning them with its poison, then dragging and shaking them to death. The detestation and horror this species arouses in human beings is hardly justified – its poison is not more troubling to a human than a bee sting.

Reputation and significance

Spiders have a very negative image among human beings. Perhaps the number of legs, the grotesque facial expression, the hairiness of some species, the fact that they carry a poison, but most of all, the fact that they hide in corners and come out unexpectedly – have contributed to the spiders’ bad reputation. The poison of spiders, with just two exceptions (the ‘black widow’ and the ‘brown recluse’), is relatively harmless to humans.

Spider silk cannot economically be converted into silk cloth for human use. However, it has been used for the cross-hairs of optical instruments. More recently, the silk of the tropical species Nephila has been employed in the manufacture of bullet-proof jackets. The Nephila spin huge webs strung across trees, as long as 2 metres or more, and of a silk so strong and elastic that the local peoples make very effective fishing nets from it.

On balance, it is high time human beings overcame their irrational detestation of spiders. We should be grateful to them for all the good they do for us in preserving our persons and properties, especially our crops, against devastation by insects. One authority calculated the spider population of England and Wales as of the order of 2.5 billions at any one time. This means that if (at a most conservative estimate) each spider eats 100 insects a year, then the total number of insects consumed by spiders is 250 billions annually.

REFERENCES

‘Spiders’ Microsoft (R) Encarta. Copyright (c) 1994 Microsoft Corporation. Copyright (c) 1994 Funk & Wagnall’s Corporation.

Buton, M. & Buton, R. (1975) Enevlopedia of Insects and Arachnids, BPC Publishing Ltd, London.

Gerald, L. & Wood, F.Z.S. (1982) The Guinness Book of Animal Facts and Feats, Guinness Superlative Ltd, London.

Waterson, AR. (ed.) (t975), Collins Enevlopedia of Animals, William Collins Sons & Co Ltd, London and Glasgow.

SPIDERS IN GUINESS BOOK OF RECORDS

The largest and the heaviest spider: The Guyanan ‘bird-eating’ spider (Theraphosa

blondi) of South America has long been credited with the ‘largest spider’ title. A male specimen with a leg-span of 254mm (10 in) and a body length of 89mm (3.5 in) weighed just under 57g (2 oz).

The smallest spiders are the midget spiders (Symphytognathidae), the tiniest of which is the pale yellow Patu marplesi of Western Samoa, S.W. Pacific. A male specimen found in moss at an altitude of 610m (2000 if) measured 0.43mm (0.07 in), which means it is half the size of a full-stop on this page!

The largest spider webs are the aerial ones spun by the tropical orb weavers of the genus Nephila. Several examples found in the Karrakpur Hills near Monghyr, central Bihar, India measured 1.5m (5ft) in diameter (about 4.79m (1 5ft 9in) in circumference) and had long supporting guy-lines up to 6.1 m (2Oft) in length.

The smallest webs in the world are the aerial ones spun by midget spiders. That of the orb weaver Chasmoeephaion armaturn of New Zealand measures about 9-10mm (O.35-0.39in.) in diameter which means it is half the size of a small postage stamp.

The highest speed recorded for a spider on a level surface is 53cm/s (1 .73ft/s) (= 1.90km/h; 1.18 miles/h) for a female house spider, Tegenaria atrica. This may not seem very fast, but the spider covers a distance equivalent to 330 times its own body length in ten seconds.