Criterion Insurance Co. an automobile insurer affiliated with Government Employees Insurance Co., reported a decline in third-quarter and nine-month earnings.

Profits from underwriting insurance declined to $750,000 in the first nine months compared with $3.1 million a year earlier, mainly because of a $2.2 million decrease in credits for deferred acquisition costs.

As a result, earnings in the third quarter dipped to $1.3 million (89 cents a share) from $1.5 million ($1.04) last year, not counting capital gains or losses. When capital gains of $94,000 and a tax credit of $272,000 are added to the recent quarter's results, net income is $1.66 million ($1.14) vs. $2.29 million ($1.57) a year earlier, which included capital losses of $64,000 and tax credits of $835.000.

For the first nine months, not counting capital gains or losses, Criterion earned $3.86 million ($2.65) compared with $4.38 million ($3), the company said yesterday. Net income was $4.5 million ($3.11) vs. $6.7 million ($4.60).

Premiums earned totaled $52 million in the first nine months compared with $49 million in the 1977 period.

United Services Life Insurance Co., meantime, has posted a 15 percent gain in nine-month profits. Earnings from operations were $5.7 million compared with $4.9 million. Including investments gains and losses, net income was $5.7 million ($1.81 a share) compared with $4.9 million ($1.56).

New life premiums totaled $2.7 million in the recent nine months, up 18 percent from last year for the company, which sells exclusively to active and former military officers and their families.

In the third quarter, United Services reported net income of $1.86 million (60 cents) vs. $1.67 million (53 cents). Life policies in force was $2.9 billion on Sept. 30, of which $2.3 billion was ordinary life insurance.

Baltimore Gas Electric Co. third-quarter profits rose to $34.6 million (97 cents a share) from 31.5 (89 cents) in the same period last year as revenues rose to $250 million from $198 million.

In the first nine months, BG&E earned $102 million ($2.89) vs. $84 million ($2.39) and revenues were up to $738 million from $596 million. The Baltimore-based utility firm, which had suffered from a depressed level of profitability last year, said electricity sales rose 4.6 percent in the first nine months compared with 1977 levels. Natural gas sales increased 7 percent.

Noxell Corp., a Baltimore cosmetics manufacturer, reported third-quarter profits of $2.27 million (45 cents a share) compared with $1.9 million (38 cents), as sales increased to $37 million from $34 million. Nine-month earnings were $8.7 million ($1.71) vs. $7.95 million ($1.57) as sales increased to $121 million from $110 million.

Strother Drug Co., of Lynchburg, reported record profits for the first fiscal quarter ended Sept. 30 or $267,000 (32 cents a share) compared with $253,000 (30 cents) last year as sales rose 10 percent to a record $10.5 million.