Skin contact with Lonomia caterpillar bristles causes a consumptive coagulopathy. From a cDNA library we cloned and expressed a prothrombin activator (rLopap) in active form, and from the bristles extract we characterized a FX activator (Losac). Several clones were sequenced and analyzed by expressed sequence tags. A database of about 1,270 sequences was constructed and deposited in NCBI. Both the native protein from the venom (Lopap) and the recombinant form (r-Lopap) promoted prothrombin hydrolysis, generating prethrombin-2, F1.2 and thrombin. Losac is a single-chain (43 kDa) protein that cleaves the FX heavy chain producing FXaα. In HUVECs rLopap and Losac are able to modulate cell survival by preventing apoptosis. rLopap increases NO and PGI2 concentration and Losac induces t-PA expression. Finally, to identify the venom proteins related to human envenomation, a 2D electrophoresis map is being performed as an attempt to find the major toxins recognized by the anti-lonomia venom.