The only insect judged to be halal is the locust; the same is true in kashruth.
Ibn Abu Aufa said: "
We went on seven expeditions with Allah's Messenger (s.a.s.) and ate locusts."
— Sahih Bukhari, Book 021, Number 4801
Ibn Abi Awfa (r.a.a.) was asked about consuming of a locust and he said:
"I fought with the Messenger of Allah (s.a.s.) in six or seven battles, and we used to eat it (locust) with him."
— Sunan Abu Dawud, Number 3806
[AMNA Note: for more information about parrallels and differences between Islamic and Jewish dietary law (kashruth), see our section: Kosher v. Halal]
Narrated at-Talabb ibn Tha'labah at-Tamimi:
"I accompanied the Apostle of Allah (peace_be_upon_him), but I did not hear about the prohibition of (eating) insects and little creatures of land."
—Sunnan Abu Dawoud, Kitab Al-At'ima. Book 27: 3789
'Abdullah b. 'Abbas reported:
"I and Khalid b. Walid went to the apartment of Maimuna along with Allah's Messenger (may peace be upon him), and there was presented to him a roasted lizard (dabb). Allah's Messenger (may peace be upon him) stretched his hand towards It, whereupon some of the women who had been in the house of Maimuna said: 'Inform Allah's Messenger (may peace be upon him) what he intends to eat.' Allah's Messenger (may peace be upon him) lifted his hand. I said: 'Messenger of Allah, Is it forbidden?' He said: 'No. It is not found in the land of my people, and I feel that I have no liking for it.' Khalid said: 'I then chewed and ate it, while, Allah's Messenger (may peace be upon him) was looking (at me).'
—Sahih Muslim, Book 021, Number 4790
Narrated Abdullah ibn Abbas:
"I was in the house of Maymunah. The Prophet, accompanied by Khalid ibn al-Walid entered. Two roasted long-tailed lizards (dabb) placed on sticks were brought to him. The Prophet (s.a.s.) spat. Khalid said: 'I think that you abominate it, O Prophet of Allah.' He said: 'Yes.' Then the Prophet of Allah was brought milk, and he drank it. The Prophet of Allah then said: 'When one of you eats food, he should say: "O Allah, bless us in it, and give us food better than it." When he is given milk to drink, he should say: "O Allah! Bless us in it and give us more of it," for no food or drink satisfies like milk.'"
Narrated Thabit ibn Wadi'ah:
"We were in an army with the Prophet (s.a.s.). We got some lizards (dabb). I roasted one lizard and brought it to the Prophet of Allah (s.a.s.) and placed it before him. He took a stick and counted its fingers. He then said: 'A group from the children of Isra'il were transformed into an animal of the land, and I do not know which animal it was.' He did not eat it, nor did he forbid (its eating).
— Abu Dawoud. Book 27, 3786
Narrated AbduRahman ibn Shibl: "The Prophet of Allah (s.a.s.) forbade eating the flesh of lizard."
— Abu Dawoud. Book 27, 3787
ISLAMIC SCHOOLS OF THOUGHT
All Islamic Schools of Jurisprudence disallow the eating of insects.
The Hanafi School of fiqh:
Within Hanafi fiqh, those land animals that have no blood in them, such as a hornet, fly, spider, beetle, scorpion, ant, etc. are considered haram, because a sound natured person would detest their consumption. The only exception is that of a locust, for the Messenger of Allah (Allah bless him & give him peace) clearly permitted its consumption, in the Hadith of Sunan Abu Dawud quoted earlier.
Within the Hanifi School of Islamic Jurisprudence, those land-animals who have blood in them but the blood does not flow, are also considered haram, such as a snake, lizard, chameleon, etc. (See below)
The Hanbali School of fiqh:
Within Hanbali fiqh, insects are not permitted because they are injurious:
"Among [the creatures] it is forbidden to be eaten are those which feed on carrion (dead meat)... owing to the evil food they feed on [so] it is prohibited to eat insects, as they are injurious."
— Al Fawzan, Dr. Salih (Professor of Islamic Jurisprudence. Member, The Permanent Committee on Fatwa and Research). "A Summary of Islamic Jurisprudence, Vol. 2," Section XI: Food, Chapter 1, p. 654.
Saudi Arabia prohibits carmine (cochineal), a red-rust food coloring made from ground carmine beetles, for use in foods imported into or sold in the Kingdom.
USDA Gain Report. "Saudi Arabia: Food and Agricultural Import Regulations and Standards" [PDF]
‘Abd al-Rahmaan ibn ‘Uthmaan, who said: "When a physician consulted the Prophet (s.a.s.) about putting frogs in medicine, he forbade him to kill them."
— Abu Dawoud 41/5249
The rule is that everything which we are forbidden to kill, we are not allowed to eat; if we are allowed to eat it we are allowed to kill it.
Saudi Arabia prohibits the importation of frog legs into the Kingdom.
USDA Gain Report #SA6016: "Saudi Arabia Retail Food Sector Update." [PDF]
SNAKES & SCORPIONS
Shaikh al-Islam Ibn Taymiyah says:
"It is unanimously agreed upon among Muslim scholars that eating snakes and scorpions is prohibited. Therefore, if any one eats such animals regarding them as lawful to be eaten, he is to be urged to repent (for denying an agreed upon legal ruling), and whoever regards them as prohibited foods but eats them is considered sinful and defiantly disobedient to Allah and His Messenger (s.a.s.)."
— Ibn Taymiyah, Majmu' ul-Fatawa. (11/690)