Delegates wishing to collect insects either before or after the congress must make their own arrangements for acquiring the proper permits. Groups going to the same areas may apply together.
An excellent general resource for information about collecting permits is at https://www.theskepticalmoth.com/collecting-permits/. The best advice is given on that page - "Collecting abroad requires a lot of planning in advance." If you are hoping to collect before or after the Congress, be sure to heed that idea!
For collecting insects within the California State Parks system, researchers are required to hold a Scientific Research and Collecting Permit. It is recommended that applications be submitted at least 60 days in advance of the first planned field activity. California State Parks are administered regionally, within Park Districts. Applications should be directed to the appropriate Park District where collecting will occur and may be submitted online. For multi-district collecting, permits should be addressed to the Environmental Program Manager, Natural Resources Division in Sacramento: nrd.research@parks.ca.gov; +1 (916) 653-6725.
No permits are required to collect insects.
Forest Service and Bureau of Land Management
Insect collecting is allowed in most public lands administered by the U.S. National Forest and the Bureau of Land Management throughout California and Nevada as long as it is non-commercial and not disruptive to the wilderness environment. In California, when collecting involves certain special species of concern, or if there is the potential for by-catch of such species, a scientific collecting permit (SCP) is needed from the California State Department of Fish and Wildlife (CDFW). For most cases, such a permit is not necessary for Dipterists, but if you suspect you may need a CDFW SCP, please consult the pre-application guide for further information.
National Parks
Applications for collecting within the U.S. National Parks system are handled through the National Park Service Research Permit and Reporting System (RPRS), with administration by each individual park (that is, there are no regional or blanket permits issued). Again, allowing at least 60 days in advance of planned collecting is recommended.
If you have additional questions, contact Peter Kerr (peter.kerr@cdfa.ca.gov)