During the hot days of August and September, the citizens of Washington and nearby Maryland and Virginia are generally hard pushed to find something to rejoice about, so the annual return of good taste should not be overlooked.

The good taste referred to here is in food -- not in manners, morals, movies or men, although some could be used in these places also. Anyone who dines on steamed blue crabs, vine-ripened tomatoes, green lima beans and fresh corn on the cob knows that this annual return of good taste during August and September is no small blessing.

However, some people contend that only the last three items should be called late-summer delights. Steamed crabs, they say, begin in June and last all summer. Nevertheless, it apparently takes a month or two for most people to get back in the swing of good eating after the long winter layoff, and some experts even swear that steamed crabs taste better in August and September than they do in June and July.

This claim may be mostly imagination coupled with the special effect produced by cold beer in very hot weather, but there also may be some substance to it because taste is a delicate thing, easily altered. A few molecules of this or that can make the difference between a dish that is a delight and another that is just grub.

It is true that a blue crab (Calinectes sapidus) is a blue crab whether he is caught during June or August, but it is a fact admitted by all that only fat crabs have that special taste that causes them to rank even higher than Maine lobsters. And it is quite possible that August crabs are fatter than June crabs, which may still be recovering from a hard winter.

Veteran eaters of steamed crabs know all this and they also know that the way to tell fat crabs from poor ones is to heft them. The heavy crabs are the fat ones.

Many veteran crab eaters can be found lifting up first one crab and then another from the platter in front of them. When asked what they are doing, they usually say they are looking for a crab with less pepper on it -- or one with more. They are not. They are picking out the fattest and tastiest crabs and leaving the others for their fellow diners.

By August or September a Chesapeake Bay blue crab probably senses that he will soon have to burrow in the mud and so will need enough fat to last him through the winter. So he stores up all the fat he can, just like a bear or a groundhog does in getting ready for hibernation. Also, the phytoplankton in the bay, those billions of trillions of tiny plants that start the food chain on which the crab feeds, probably grow more lushly under the August sun than they do in June, and all good taste may really have its start in lush plant life. For example, look at corn, beans and tomatoes.

Corn can be used to produce such tasty products as cornpone, grits, country ham and bourbon whiskey, but, even better than all these, it can be eaten right off the cob. And while it may be debatable as to whether August crabs taste better than the June variety, no one denies the fact that a vine- ripened August tomato is vastly superior to one of those tough, green things grown in Florida during the winter and ripened with ethylene gas on the way to the market.

The difference in taste is so great that chemists have even fancied they might be able to analyze tomatoes for the various acids, esters, ketones, lactones, sugars and terpenes and then fortify a winter tomato to make it taste like a vine-ripened August tomato.

Alas, this has never worked, because the chemists found that both January tomatoes and the vine-ripened ones from Maryland and Virginia all have the same malic, maleic, ascorbic and acetic acids in them, in about the same ratio, even though they differ as much in taste as sawdust and fresh gingerbread do.

It is the same way with fresh sweet corn and green lima beans. They taste no more like the frozen brands than August tomatoes taste like those small red golf balls shipped in from Florida, but the chemicals in them are astonishingly alike.

It is all very confusing to the chemists, who have slowly come to realize that they need to refine their analytical techniques a thousand-fold or maybe a million-fold before they can analyze for the chemical ingredients which make good taste.

In the meantime, let all Washingtonians sit down and feast on the good tastes of August and September. Two plates and a tall glass are needed. One plate for the vegetables, one for the steamed crabs.

The tall glass should be chilled before the beer is poured in it.