The most apparent indication of serious pesticide poisoning is the sudden loss of adult bees. This loss is characterized by the appearance of many dead and dying adult bees and sometimes pupae at the colony entrances. However, in many instances, the bees are lost in the field before returning to the colony. If the pesticide is brought back to the hive by the foragers, the nurse bees are killed when they feed on contaminated honey or pollen and the brood will exhibit symptoms of neglect or poisoning. The symptoms of poisoned honey bees often depend on the class of pesticide involved (table 4).

A residue of a pesticide may be present as the original pesticide, or as an identifiable degradation product, or both. Frequently, the amount of residue is extremely small. Pesticide analysis consists primarily of the following (from Wilson et al. 1980):

(1) Blending and extraction of the biological material (such as bees or pollen) with a suitable solvent system to maximize the recovery of suspected pesticides and their metabolites. This eliminates the bulk of the biological substrate.

(2) A series of liquid-liquid extractions and column chromatographs to further separate the residues from other materials of biological origin. A very fast method for cleanup is gel permeation chromatography. Large molecules of biological origin emerge from the column first, thereby directly trimming the crude extract down to a much cleaner sample.

(3) Detection of residues at the highest possible sensitivity to avoid interference from substances not previously removed. The most popular detection system is gas-liquid chromatography, wherein the residue-containing sample is volatilized and chromatographed as a vapor. Thin-layer and paper chromatography are also useful for establishing the identity of pesticide residues. Visualization for detection usually involves spraying the chromatograms with a chemical that reacts with the pesticide or metabolite to produce a characteristic color. Other methods used for residue analysis include mass spectroscopy and fluorometric techniques. The residue must be capable of absorbing visible light or ultraviolet light. The intensity of the remitted light is measured at some suitable wavelength and compared with standards.

Table 4. Typical symptoms of pesticide poisoning

Class of pesticide	Examples of pesticides	Symptoms of poisoning
Organo- phosphorous	Parathion, methyl parathion, dimethoate (Cygon), naled (Dibrom), mevinphos (phosdrin), diazinon, dichlorvos (Vapona), monocrotophos (Azodrin), malathion, tepp, phorate (thimet), phosphamidon (Dimecron), chlorpyyrifos (Dursban)	Regurgitation (bees are wet); disorientation, lethargy. Perhaps distended abdomen, erratic attempts to clean selves, tumbling about, paralysis, ultimately death. Wings held away from body but usually remaining hooked together. High percentage of poisoned bees die at colony.
Chlorinated hydrocarbon	Aldrin, chlordane, DDT, dieldrin, heptachlor, lindane, toxaphene	Erratic movements, abnormal activities, trembling. Hindlegs dragging as if paralyzed and wings held away from body but usually remaining hooked together. High percentage of poisoned bees die in field as well as at the colony.
Carbamate	Carbaryl (Sevin), carbofuran (Furadan), aminocarb (Matacil), dimethilan (Dimetilane), mexacarbate, methomly (lannate, Nudrin)	Aggressiveness, erratic movements; then inability to fly, stupefaction as though chilled; followed by paralysis, morbidity, death. Most bees usually die at colony. Queens often cease egg laying; hive bees initiate supersedure, rearing queens before egg laying resumes.
Dini-trophenyl	Dinocap (karathane), DNOC, DNOCHP, DNOSBP	Similar to symptoms of chlorinated hydrocarbons but often accompanied by regurgitation of substances in digestive tract, as is typical of organophosphorous pesticides. Most affected bees usually die at colony.
Botanical	Pyrethrum, allethrin, and the pryethroid: resmethrin, bioresmethrin, bioethanomethrin, and cismethrin; also nicotine, rotenone, ryania, sabadilla	Perhaps regurgitation from highly toxic pyrethroids, together with erratic movements; then inability to fly and stupefaction, followed very soon by paralysis, moribundity, and death. Bees often die between foraging area and colony.