There are approximately 3000 species of spiders in North America and all are poisonous. However, most of them are too small, don’t have biting apparatuses strong enough to penetrate human skin or have too little poison to be a threat to humans. There may be a mild reaction at the site of the bite, but any severe reaction from a spider bite is usually delayed from 1 to 8 hours. The two most common species of spiders that are considered health threats are the black widow and brown recluse. There are no brown recluse spiders in Canada, but there are black widow spiders, some of which may be brought into the country in produce imported from the south. Eighty percent of suspected spider bites have been found to be due to ants, fleas, bedbugs, ticks, mites, mosquitoes and biting flies.. – Psoriasis, seborrheic dermatitis, prurigo, discoid lupus erythematosus, and insect bite reactions. Dosage and Administration: A small quantity of BETADERMeshould be applied gently to the affected area once or twice daily until improvement occurs, and then only once a day to maintain improvement. The effect of BETADERM may be increased, if necessary, in the more resistant lesions, by occlusive dressings.. Bites from ants may cause a painful, itchy raised pustule. Location of bite may give some clue as to the type of insect which caused it: Flying insects tend to bite or sting exposed skin areas. Flea bites are likely to be on the lower legs and around the waist, often occurring in clusters. Bedbugs may bite in clusters, usually around the head and neck.