Mesa of Lost Women

The film opens with a brief scene serving as its introduction. A man is being caressed by feminine hands. The next shot includes the face of the woman, Tarantella (Tandra Quinn). A brief kiss between her and the man, ends with his lifeless body falling down. A disembodied voice asks the audience "Have you ever been kissed by a girl like this?" [1] The narrative properly begins in a desert. A narrator (Lyle Talbot) mocks the overblown ego of humanity, a race of puny bipeds which claims to own planet Earth and every living thing on it. Yet, they are outnumbered by the insects, and the Hexapods are likely to survive longer than humans.[1] The narrator then claims that when men or women venture off "the well beaten path of civilization" and deal with the unknown, the price of their survival is the loss of their sanity.[1]
During this narration, the film introduces its protagonists Grant Phillips (Robert Knapp) and Doreen Culbertson (Paula Hill). The narrator explains that the two of them are lost in the "great Mexican desert", the "Muerto desert".[1] They are nearly dead from dehydration and sunburn when discovered by an American surveyor and his Mexican companion. These characters are identified as Frank (John Martin) and Pepe (Chrispin Martin).[1] The two victims of the desert recover their senses in "Amer-Exico Field Hospital", somewhere in Mexico. Grant starts narrating his story to Doc Tucker (Allan Nixon), foreman Dan Mulcahey (Richard Travis), and Pepe.[1]
The film flash-backs to events occurring a year earlier in Zarpa Mesa. Famous scientist Leland Masterson (Harmon Stevens) arrives, having accepted an invitation Dr. Aranya (Jackie Coogan). Aranya (name derived from the Spanish araÃ±a for spider) has reportedly penned "brilliant" scientific treatises, and Masterson looks forward to meeting him in person. Masterson is genuinely intrigued by Aranya's theories, but his host informs Masterson that his work is not theoretical. He has already completed successful experiments, creating both human-sized tarantula spiders and human women with the abilities and instincts of spiders.[1] His creation Tarantella has regenerative abilities, sufficient to regrow severed limbs. He seriously expects her to have a lifespan of several centuries.[1] His experiments have had less success in male humans, who simply turn to disfigured dwarfs.[1]
Masterson is horrified and denounces Aranya and his creations, proclaiming that they should be destroyed. In response, Aranya has him injected with a drug, turning him into a doddering simpleton. The front page of a newspaper called Southwest Journal explains that Masterson was eventually found wandering in the desert. He was declared insane and placed in an asylum.[1] Some time later, Masterson escapes the "Muerto State Asylum". He is next seen two days later, in an unnamed American town of the MexicoâUnited States border. Also present there are Tarantella, businessman Jan van Croft (Nico Lek), and his fiancÃ©e Doreen. They were heading to Mexico for their wedding day, but their private airplane had engine problems and stranded them there.[1] Jan's servant Wu (Samuel Wu) is seen exchanging glances with Tarantella. It serves as the first sign that he is working with her.[1]
Masterson is tracked to the bar by his nurse at the asylum, George (George Barrows). The entire bar and its patrons observe Tarantella perform an energetic dance. Masterson apparently recognizes her, pulls a handgun, and shoots her. He then takes Jan, Doreen, and George hostage. He heads for Jan's private airplane and he forces pilot Grant to prepare for takeoff, despite the pilot's protests that only one engine is fully functional. The airplane departs with Doreen, George, Grant, Jan, Masterson, and Wu aboard it.[1] Meanwhile, Tarantella regenerates following her apparent death, and leaves the bar.[1]
In mid-flight, Grant discovers that someone sabotaged the gyrocompass, resulting in them flying towards the wrong direction for most of the flight. Wu's facial expression allows the audience to learn who was the saboteur. The airplane crash-lands atop Zarpa Mesa, where the creations of Aranya were expecting them. For a while being, the creations simply observe them from afar.[1] The film follows the activities of the stranded group for quite a while. There is sexual tension between Grant and Doreen, culminating in a passionate kiss. Meanwhile, the group dwindles with the deaths of first George, secondly Wu, and lastly Jan. Wu is confirmed to have served as an agent of Aranya, but one who outlived his usefulness.[1]
The last three members of the group are then captured. Grant soon recognizes that their captor's name is identical to the Spanish term for "spider", "araÃ±a". Aranya cures Masterson from drug-induced imbecility, hoping to recruit him. This backfires as Masterson uses his intellect in a suicide attack. He allows Doreen and Grant to escape, then sets up an explosion which kills himself and everyone else.[1] The flashback ends and we return to the hospital. He fails to convince anyone but Pepe of the truth in his story. Yet the finale reveals that at least one of Aranya's spider-women has survived.[1]

Question: What did masteron use in his suicide attack?
Answer: His intellect.