SB 10.20.8

niśā-mukheṣu khadyotās
 tamasā bhānti na grahāḥ
yathā pāpena pāṣaṇḍā
 na hi vedāḥ kalau yuge
Word for word: 
niśā-mukheṣu — during the moments of evening twilight; khadyotāḥ — the glowworms; tamasā — because of the darkness; bhānti — shine; na — not; grahāḥ — the planets; yathā — as; pāpena — because of sinful activities; pāṣaṇḍāḥ — atheistic doctrines; na — and not; hi — certainly; vedāḥ — the Vedas; kalau yuge — in the Age of Kali.
Translation: 
In the evening twilight during the rainy season, the darkness allowed the glowworms but not the stars to shine forth, just as in the Age of Kali the predominance of sinful activities allows atheistic doctrines to overshadow the true knowledge of the Vedas.
Purport: 

Śrīla Prabhupāda comments as follows: “During the rainy season, in the evening there are many glowworms visible about the tops of trees, hither and thither, and they glitter just like lights. But the luminaries of the sky — the stars and the moon — are not visible. Similarly, in the Age of Kali, persons who are atheists or miscreants become very prominently visible, whereas persons who are actually following the Vedic principles for spiritual emancipation are practically obscured. This age, Kali-yuga, is compared to the cloudy season of the living entities. In this age, real knowledge is covered by the influence of the material advancement of civilization. The cheap mental speculators, atheists and manufacturers of so-called religious principles become prominent like the glowworms, whereas persons strictly following the Vedic principles or scriptural injunctions become covered by the clouds of this age. People should learn to take advantage of the actual luminaries of the sky — the sun, moon and stars — instead of the glowworms’ light. Actually, the glowworms cannot give any light in the darkness of night. As clouds sometimes clear, even in the rainy season, and sometimes the moon, stars and sun become visible, so even in this Kali-yuga there are sometimes advantages. The Vedic movement of Lord Caitanya — the distribution of the chanting of the Hare Kṛṣṇa mantra — is understood in this way. People seriously eager to find real light should take advantage of this movement instead of looking toward the light of mental speculators and atheists.”