ARE there mosquitoes in the mountains?'' I asked Nilo, my jeepney driver, as we approached the Lobo mountain range in the southern part of the Philippine province of Batangas. Just before departing for Southeast Asia, I had been advised to take plenty of insect repellent if I traveled far from urban areas.
''Not so many,'' Nilo replied at last, a slight grin appearing on his face, ''but very dangerous ones. The mosquitoes here have rifles.''
The members of the Communist New People's Army (NPA) - the ''mosquitoes'' that Nilo referred to - are virtually everywhere in the rural Philippines, today numbering between 12,000 and 20,000. Despite the government's efforts to hunt them down, their strength is growing every day, assisted by the current economic crisis, which has impoverished hundreds of thousands of rural dwellers. A year ago, Francisco Nemenzo, formerly a ranking member of the Philippine Communist Party and today an academic at the Australian National University where he is writing a book about the ongoing rural revolution in the Philippines, estimated that the NPA could count on the support of no fewer than a million Filipinos on the island of Luzon alone. Today, in the aftermath of three devaluations, constant price increases, and the steady drain of foreign capital, the number of NPA supporters could easily be twice as large.
The NPA is not preparing a full-scale attack on the Philippine government in the immediate future. The lessons learned from the abortive Huk Rebellion (1946- 54), put down with United States assistance, and the Vietnamese struggles against France and the US have convinced NPA leaders that they must avoid a premature bid for power. NPA strategists have drawn up a 10- to 20-year game plan, calling for continuing rural recruitment and stepped-up organizational activity among the urban poor, the establishment of secure strategic areas, and a gradually escalating military campaign. They firmly believe, as one NPA sympathizer told me six weeks ago, that ''by the year 2000 we (the Communists) will have liberated the Philippines.''
In contrast to the well-organized mosquitoes in the mountains, the urban-based above-ground opposition groups in the Philippines are in disarray. The on-again, off-again alliance of establishment critics of the Marcos regime, led by Salvador Laurel, and various worker/stu-dent/radical groups is simply a marriage of convenience. The only thing that they have in common is a conviction that President Marcos must be replaced. They disagree fundamentally about tactics and programs, with the students and other radical elements calling for major social reforms and the elimination of US bases while Mr. Laurel and his allies emphasize the return to democratic government and the restoration of traditional freedoms.
Furthermore, as a leader, Mr. Laurel excites little enthusiasm. Typical of the old-style Filipino politician, he is a wealthy man with a strong, secure power base in the provinces. ''Laurel is only a marginal improvement over Marcos ,'' a student radical told me in September. ''We really don't trust the guy.''
In light of the inability of the above-ground opposition groups to identify a viable leader, the future of the Philippines looks grim indeed. Marcos will undoubtedly try to hold on as long as he can; only a few days ago he announced his intention to run for reelection in 1987.
Eventually, it seems likely that some combination of three groups will take over: Marcos's wife, Imelda, and her faction; a military clique led by Gen. Fabian Ver (or possibly by another Ilocano general if General Ver's indictment for involvement in the Aquino assassination removes him from the succession picture); and a contingent of technocrats, including Prime Minister Cesar Virata. Of all the possible scenarios, the most likely seems to be an Imelda-Army alliance, with Imelda being gradually pushed out by mounting public pressure to step down.
Clearly, the Reagan administration wants to prevent such a turn of events. But in the long run, Marcos's ability to survive will depend on his handling of the economic crisis and (to a lesser extent) the prosecution of General Ver and the others implicated in the Aquino assassination. Both problems are formidable.
If Marcos were forced to step down tomorrow and if he called for immediate elections, who would be able to gain sufficient popular support to form a viable government? Both Washington and the supporters of Mr. Laurel are concerned. ''We have to come up with someone within the next four months,'' a leading figure in the Laurel camp confided. ''If we don't, it could be disastrous.''
Each scenario poses major problems. If Marcos remains as President, he may be unable to solve the economic crisis; if he dies, the military almost certainly will take over. If elections are held, the elected government may lack sufficient popular support and become unstable. When one considers the possibilities, it is easy to see why the NPA is so confident about its long-term prospect of coming to power. With each passing day, as economic and political conditions deteriorate and as the power brokers in Manila continue to plan and plot, more and more mosquitoes are appearing in the mountains.